1.1 --- a/extensions/sqlite/sqlite-source/where.c Fri Jul 11 06:51:21 2008 +0000
1.2 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000
1.3 @@ -1,2773 +0,0 @@
1.4 -/*
1.5 -** 2001 September 15
1.6 -**
1.7 -** The author disclaims copyright to this source code. In place of
1.8 -** a legal notice, here is a blessing:
1.9 -**
1.10 -** May you do good and not evil.
1.11 -** May you find forgiveness for yourself and forgive others.
1.12 -** May you share freely, never taking more than you give.
1.13 -**
1.14 -*************************************************************************
1.15 -** This module contains C code that generates VDBE code used to process
1.16 -** the WHERE clause of SQL statements. This module is reponsible for
1.17 -** generating the code that loops through a table looking for applicable
1.18 -** rows. Indices are selected and used to speed the search when doing
1.19 -** so is applicable. Because this module is responsible for selecting
1.20 -** indices, you might also think of this module as the "query optimizer".
1.21 -**
1.22 -** $Id$
1.23 -*/
1.24 -#include "sqliteInt.h"
1.25 -
1.26 -/*
1.27 -** The number of bits in a Bitmask. "BMS" means "BitMask Size".
1.28 -*/
1.29 -#define BMS (sizeof(Bitmask)*8)
1.30 -
1.31 -/*
1.32 -** Trace output macros
1.33 -*/
1.34 -#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
1.35 -int sqlite3_where_trace = 0;
1.36 -# define WHERETRACE(X) if(sqlite3_where_trace) sqlite3DebugPrintf X
1.37 -#else
1.38 -# define WHERETRACE(X)
1.39 -#endif
1.40 -
1.41 -/* Forward reference
1.42 -*/
1.43 -typedef struct WhereClause WhereClause;
1.44 -typedef struct ExprMaskSet ExprMaskSet;
1.45 -
1.46 -/*
1.47 -** The query generator uses an array of instances of this structure to
1.48 -** help it analyze the subexpressions of the WHERE clause. Each WHERE
1.49 -** clause subexpression is separated from the others by an AND operator.
1.50 -**
1.51 -** All WhereTerms are collected into a single WhereClause structure.
1.52 -** The following identity holds:
1.53 -**
1.54 -** WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
1.55 -**
1.56 -** When a term is of the form:
1.57 -**
1.58 -** X <op> <expr>
1.59 -**
1.60 -** where X is a column name and <op> is one of certain operators,
1.61 -** then WhereTerm.leftCursor and WhereTerm.leftColumn record the
1.62 -** cursor number and column number for X. WhereTerm.operator records
1.63 -** the <op> using a bitmask encoding defined by WO_xxx below. The
1.64 -** use of a bitmask encoding for the operator allows us to search
1.65 -** quickly for terms that match any of several different operators.
1.66 -**
1.67 -** prereqRight and prereqAll record sets of cursor numbers,
1.68 -** but they do so indirectly. A single ExprMaskSet structure translates
1.69 -** cursor number into bits and the translated bit is stored in the prereq
1.70 -** fields. The translation is used in order to maximize the number of
1.71 -** bits that will fit in a Bitmask. The VDBE cursor numbers might be
1.72 -** spread out over the non-negative integers. For example, the cursor
1.73 -** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The ExprMaskSet
1.74 -** translates these sparse cursor numbers into consecutive integers
1.75 -** beginning with 0 in order to make the best possible use of the available
1.76 -** bits in the Bitmask. So, in the example above, the cursor numbers
1.77 -** would be mapped into integers 0 through 7.
1.78 -*/
1.79 -typedef struct WhereTerm WhereTerm;
1.80 -struct WhereTerm {
1.81 - Expr *pExpr; /* Pointer to the subexpression */
1.82 - i16 iParent; /* Disable pWC->a[iParent] when this term disabled */
1.83 - i16 leftCursor; /* Cursor number of X in "X <op> <expr>" */
1.84 - i16 leftColumn; /* Column number of X in "X <op> <expr>" */
1.85 - u16 eOperator; /* A WO_xx value describing <op> */
1.86 - u8 flags; /* Bit flags. See below */
1.87 - u8 nChild; /* Number of children that must disable us */
1.88 - WhereClause *pWC; /* The clause this term is part of */
1.89 - Bitmask prereqRight; /* Bitmask of tables used by pRight */
1.90 - Bitmask prereqAll; /* Bitmask of tables referenced by p */
1.91 -};
1.92 -
1.93 -/*
1.94 -** Allowed values of WhereTerm.flags
1.95 -*/
1.96 -#define TERM_DYNAMIC 0x01 /* Need to call sqlite3ExprDelete(pExpr) */
1.97 -#define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */
1.98 -#define TERM_CODED 0x04 /* This term is already coded */
1.99 -#define TERM_COPIED 0x08 /* Has a child */
1.100 -#define TERM_OR_OK 0x10 /* Used during OR-clause processing */
1.101 -
1.102 -/*
1.103 -** An instance of the following structure holds all information about a
1.104 -** WHERE clause. Mostly this is a container for one or more WhereTerms.
1.105 -*/
1.106 -struct WhereClause {
1.107 - Parse *pParse; /* The parser context */
1.108 - ExprMaskSet *pMaskSet; /* Mapping of table indices to bitmasks */
1.109 - int nTerm; /* Number of terms */
1.110 - int nSlot; /* Number of entries in a[] */
1.111 - WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */
1.112 - WhereTerm aStatic[10]; /* Initial static space for a[] */
1.113 -};
1.114 -
1.115 -/*
1.116 -** An instance of the following structure keeps track of a mapping
1.117 -** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
1.118 -**
1.119 -** The VDBE cursor numbers are small integers contained in
1.120 -** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE
1.121 -** clause, the cursor numbers might not begin with 0 and they might
1.122 -** contain gaps in the numbering sequence. But we want to make maximum
1.123 -** use of the bits in our bitmasks. This structure provides a mapping
1.124 -** from the sparse cursor numbers into consecutive integers beginning
1.125 -** with 0.
1.126 -**
1.127 -** If ExprMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
1.128 -** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A.
1.129 -**
1.130 -** For example, if the WHERE clause expression used these VDBE
1.131 -** cursors: 4, 5, 8, 29, 57, 73. Then the ExprMaskSet structure
1.132 -** would map those cursor numbers into bits 0 through 5.
1.133 -**
1.134 -** Note that the mapping is not necessarily ordered. In the example
1.135 -** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0,
1.136 -** 57->5, 73->4. Or one of 719 other combinations might be used. It
1.137 -** does not really matter. What is important is that sparse cursor
1.138 -** numbers all get mapped into bit numbers that begin with 0 and contain
1.139 -** no gaps.
1.140 -*/
1.141 -struct ExprMaskSet {
1.142 - int n; /* Number of assigned cursor values */
1.143 - int ix[sizeof(Bitmask)*8]; /* Cursor assigned to each bit */
1.144 -};
1.145 -
1.146 -
1.147 -/*
1.148 -** Bitmasks for the operators that indices are able to exploit. An
1.149 -** OR-ed combination of these values can be used when searching for
1.150 -** terms in the where clause.
1.151 -*/
1.152 -#define WO_IN 1
1.153 -#define WO_EQ 2
1.154 -#define WO_LT (WO_EQ<<(TK_LT-TK_EQ))
1.155 -#define WO_LE (WO_EQ<<(TK_LE-TK_EQ))
1.156 -#define WO_GT (WO_EQ<<(TK_GT-TK_EQ))
1.157 -#define WO_GE (WO_EQ<<(TK_GE-TK_EQ))
1.158 -#define WO_MATCH 64
1.159 -#define WO_ISNULL 128
1.160 -
1.161 -/*
1.162 -** Value for flags returned by bestIndex().
1.163 -**
1.164 -** The least significant byte is reserved as a mask for WO_ values above.
1.165 -** The WhereLevel.flags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
1.166 -** But if the table is the right table of a left join, WhereLevel.flags
1.167 -** is set to WO_IN|WO_EQ. The WhereLevel.flags field can then be used as
1.168 -** the "op" parameter to findTerm when we are resolving equality constraints.
1.169 -** ISNULL constraints will then not be used on the right table of a left
1.170 -** join. Tickets #2177 and #2189.
1.171 -*/
1.172 -#define WHERE_ROWID_EQ 0x000100 /* rowid=EXPR or rowid IN (...) */
1.173 -#define WHERE_ROWID_RANGE 0x000200 /* rowid<EXPR and/or rowid>EXPR */
1.174 -#define WHERE_COLUMN_EQ 0x001000 /* x=EXPR or x IN (...) */
1.175 -#define WHERE_COLUMN_RANGE 0x002000 /* x<EXPR and/or x>EXPR */
1.176 -#define WHERE_COLUMN_IN 0x004000 /* x IN (...) */
1.177 -#define WHERE_TOP_LIMIT 0x010000 /* x<EXPR or x<=EXPR constraint */
1.178 -#define WHERE_BTM_LIMIT 0x020000 /* x>EXPR or x>=EXPR constraint */
1.179 -#define WHERE_IDX_ONLY 0x080000 /* Use index only - omit table */
1.180 -#define WHERE_ORDERBY 0x100000 /* Output will appear in correct order */
1.181 -#define WHERE_REVERSE 0x200000 /* Scan in reverse order */
1.182 -#define WHERE_UNIQUE 0x400000 /* Selects no more than one row */
1.183 -#define WHERE_VIRTUALTABLE 0x800000 /* Use virtual-table processing */
1.184 -
1.185 -/*
1.186 -** Initialize a preallocated WhereClause structure.
1.187 -*/
1.188 -static void whereClauseInit(
1.189 - WhereClause *pWC, /* The WhereClause to be initialized */
1.190 - Parse *pParse, /* The parsing context */
1.191 - ExprMaskSet *pMaskSet /* Mapping from table indices to bitmasks */
1.192 -){
1.193 - pWC->pParse = pParse;
1.194 - pWC->pMaskSet = pMaskSet;
1.195 - pWC->nTerm = 0;
1.196 - pWC->nSlot = ArraySize(pWC->aStatic);
1.197 - pWC->a = pWC->aStatic;
1.198 -}
1.199 -
1.200 -/*
1.201 -** Deallocate a WhereClause structure. The WhereClause structure
1.202 -** itself is not freed. This routine is the inverse of whereClauseInit().
1.203 -*/
1.204 -static void whereClauseClear(WhereClause *pWC){
1.205 - int i;
1.206 - WhereTerm *a;
1.207 - for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
1.208 - if( a->flags & TERM_DYNAMIC ){
1.209 - sqlite3ExprDelete(a->pExpr);
1.210 - }
1.211 - }
1.212 - if( pWC->a!=pWC->aStatic ){
1.213 - sqlite3_free(pWC->a);
1.214 - }
1.215 -}
1.216 -
1.217 -/*
1.218 -** Add a new entries to the WhereClause structure. Increase the allocated
1.219 -** space as necessary.
1.220 -**
1.221 -** If the flags argument includes TERM_DYNAMIC, then responsibility
1.222 -** for freeing the expression p is assumed by the WhereClause object.
1.223 -**
1.224 -** WARNING: This routine might reallocate the space used to store
1.225 -** WhereTerms. All pointers to WhereTerms should be invalided after
1.226 -** calling this routine. Such pointers may be reinitialized by referencing
1.227 -** the pWC->a[] array.
1.228 -*/
1.229 -static int whereClauseInsert(WhereClause *pWC, Expr *p, int flags){
1.230 - WhereTerm *pTerm;
1.231 - int idx;
1.232 - if( pWC->nTerm>=pWC->nSlot ){
1.233 - WhereTerm *pOld = pWC->a;
1.234 - pWC->a = sqlite3_malloc( sizeof(pWC->a[0])*pWC->nSlot*2 );
1.235 - if( pWC->a==0 ){
1.236 - pWC->pParse->db->mallocFailed = 1;
1.237 - if( flags & TERM_DYNAMIC ){
1.238 - sqlite3ExprDelete(p);
1.239 - }
1.240 - return 0;
1.241 - }
1.242 - memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
1.243 - if( pOld!=pWC->aStatic ){
1.244 - sqlite3_free(pOld);
1.245 - }
1.246 - pWC->nSlot *= 2;
1.247 - }
1.248 - pTerm = &pWC->a[idx = pWC->nTerm];
1.249 - pWC->nTerm++;
1.250 - pTerm->pExpr = p;
1.251 - pTerm->flags = flags;
1.252 - pTerm->pWC = pWC;
1.253 - pTerm->iParent = -1;
1.254 - return idx;
1.255 -}
1.256 -
1.257 -/*
1.258 -** This routine identifies subexpressions in the WHERE clause where
1.259 -** each subexpression is separated by the AND operator or some other
1.260 -** operator specified in the op parameter. The WhereClause structure
1.261 -** is filled with pointers to subexpressions. For example:
1.262 -**
1.263 -** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
1.264 -** \________/ \_______________/ \________________/
1.265 -** slot[0] slot[1] slot[2]
1.266 -**
1.267 -** The original WHERE clause in pExpr is unaltered. All this routine
1.268 -** does is make slot[] entries point to substructure within pExpr.
1.269 -**
1.270 -** In the previous sentence and in the diagram, "slot[]" refers to
1.271 -** the WhereClause.a[] array. This array grows as needed to contain
1.272 -** all terms of the WHERE clause.
1.273 -*/
1.274 -static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){
1.275 - if( pExpr==0 ) return;
1.276 - if( pExpr->op!=op ){
1.277 - whereClauseInsert(pWC, pExpr, 0);
1.278 - }else{
1.279 - whereSplit(pWC, pExpr->pLeft, op);
1.280 - whereSplit(pWC, pExpr->pRight, op);
1.281 - }
1.282 -}
1.283 -
1.284 -/*
1.285 -** Initialize an expression mask set
1.286 -*/
1.287 -#define initMaskSet(P) memset(P, 0, sizeof(*P))
1.288 -
1.289 -/*
1.290 -** Return the bitmask for the given cursor number. Return 0 if
1.291 -** iCursor is not in the set.
1.292 -*/
1.293 -static Bitmask getMask(ExprMaskSet *pMaskSet, int iCursor){
1.294 - int i;
1.295 - for(i=0; i<pMaskSet->n; i++){
1.296 - if( pMaskSet->ix[i]==iCursor ){
1.297 - return ((Bitmask)1)<<i;
1.298 - }
1.299 - }
1.300 - return 0;
1.301 -}
1.302 -
1.303 -/*
1.304 -** Create a new mask for cursor iCursor.
1.305 -**
1.306 -** There is one cursor per table in the FROM clause. The number of
1.307 -** tables in the FROM clause is limited by a test early in the
1.308 -** sqlite3WhereBegin() routine. So we know that the pMaskSet->ix[]
1.309 -** array will never overflow.
1.310 -*/
1.311 -static void createMask(ExprMaskSet *pMaskSet, int iCursor){
1.312 - assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
1.313 - pMaskSet->ix[pMaskSet->n++] = iCursor;
1.314 -}
1.315 -
1.316 -/*
1.317 -** This routine walks (recursively) an expression tree and generates
1.318 -** a bitmask indicating which tables are used in that expression
1.319 -** tree.
1.320 -**
1.321 -** In order for this routine to work, the calling function must have
1.322 -** previously invoked sqlite3ExprResolveNames() on the expression. See
1.323 -** the header comment on that routine for additional information.
1.324 -** The sqlite3ExprResolveNames() routines looks for column names and
1.325 -** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
1.326 -** the VDBE cursor number of the table. This routine just has to
1.327 -** translate the cursor numbers into bitmask values and OR all
1.328 -** the bitmasks together.
1.329 -*/
1.330 -static Bitmask exprListTableUsage(ExprMaskSet*, ExprList*);
1.331 -static Bitmask exprSelectTableUsage(ExprMaskSet*, Select*);
1.332 -static Bitmask exprTableUsage(ExprMaskSet *pMaskSet, Expr *p){
1.333 - Bitmask mask = 0;
1.334 - if( p==0 ) return 0;
1.335 - if( p->op==TK_COLUMN ){
1.336 - mask = getMask(pMaskSet, p->iTable);
1.337 - return mask;
1.338 - }
1.339 - mask = exprTableUsage(pMaskSet, p->pRight);
1.340 - mask |= exprTableUsage(pMaskSet, p->pLeft);
1.341 - mask |= exprListTableUsage(pMaskSet, p->pList);
1.342 - mask |= exprSelectTableUsage(pMaskSet, p->pSelect);
1.343 - return mask;
1.344 -}
1.345 -static Bitmask exprListTableUsage(ExprMaskSet *pMaskSet, ExprList *pList){
1.346 - int i;
1.347 - Bitmask mask = 0;
1.348 - if( pList ){
1.349 - for(i=0; i<pList->nExpr; i++){
1.350 - mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
1.351 - }
1.352 - }
1.353 - return mask;
1.354 -}
1.355 -static Bitmask exprSelectTableUsage(ExprMaskSet *pMaskSet, Select *pS){
1.356 - Bitmask mask = 0;
1.357 - while( pS ){
1.358 - mask |= exprListTableUsage(pMaskSet, pS->pEList);
1.359 - mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
1.360 - mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
1.361 - mask |= exprTableUsage(pMaskSet, pS->pWhere);
1.362 - mask |= exprTableUsage(pMaskSet, pS->pHaving);
1.363 - pS = pS->pPrior;
1.364 - }
1.365 - return mask;
1.366 -}
1.367 -
1.368 -/*
1.369 -** Return TRUE if the given operator is one of the operators that is
1.370 -** allowed for an indexable WHERE clause term. The allowed operators are
1.371 -** "=", "<", ">", "<=", ">=", and "IN".
1.372 -*/
1.373 -static int allowedOp(int op){
1.374 - assert( TK_GT>TK_EQ && TK_GT<TK_GE );
1.375 - assert( TK_LT>TK_EQ && TK_LT<TK_GE );
1.376 - assert( TK_LE>TK_EQ && TK_LE<TK_GE );
1.377 - assert( TK_GE==TK_EQ+4 );
1.378 - return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
1.379 -}
1.380 -
1.381 -/*
1.382 -** Swap two objects of type T.
1.383 -*/
1.384 -#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
1.385 -
1.386 -/*
1.387 -** Commute a comparision operator. Expressions of the form "X op Y"
1.388 -** are converted into "Y op X".
1.389 -**
1.390 -** If a collation sequence is associated with either the left or right
1.391 -** side of the comparison, it remains associated with the same side after
1.392 -** the commutation. So "Y collate NOCASE op X" becomes
1.393 -** "X collate NOCASE op Y". This is because any collation sequence on
1.394 -** the left hand side of a comparison overrides any collation sequence
1.395 -** attached to the right. For the same reason the EP_ExpCollate flag
1.396 -** is not commuted.
1.397 -*/
1.398 -static void exprCommute(Expr *pExpr){
1.399 - u16 expRight = (pExpr->pRight->flags & EP_ExpCollate);
1.400 - u16 expLeft = (pExpr->pLeft->flags & EP_ExpCollate);
1.401 - assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
1.402 - SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
1.403 - pExpr->pRight->flags = (pExpr->pRight->flags & ~EP_ExpCollate) | expLeft;
1.404 - pExpr->pLeft->flags = (pExpr->pLeft->flags & ~EP_ExpCollate) | expRight;
1.405 - SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
1.406 - if( pExpr->op>=TK_GT ){
1.407 - assert( TK_LT==TK_GT+2 );
1.408 - assert( TK_GE==TK_LE+2 );
1.409 - assert( TK_GT>TK_EQ );
1.410 - assert( TK_GT<TK_LE );
1.411 - assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
1.412 - pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
1.413 - }
1.414 -}
1.415 -
1.416 -/*
1.417 -** Translate from TK_xx operator to WO_xx bitmask.
1.418 -*/
1.419 -static int operatorMask(int op){
1.420 - int c;
1.421 - assert( allowedOp(op) );
1.422 - if( op==TK_IN ){
1.423 - c = WO_IN;
1.424 - }else if( op==TK_ISNULL ){
1.425 - c = WO_ISNULL;
1.426 - }else{
1.427 - c = WO_EQ<<(op-TK_EQ);
1.428 - }
1.429 - assert( op!=TK_ISNULL || c==WO_ISNULL );
1.430 - assert( op!=TK_IN || c==WO_IN );
1.431 - assert( op!=TK_EQ || c==WO_EQ );
1.432 - assert( op!=TK_LT || c==WO_LT );
1.433 - assert( op!=TK_LE || c==WO_LE );
1.434 - assert( op!=TK_GT || c==WO_GT );
1.435 - assert( op!=TK_GE || c==WO_GE );
1.436 - return c;
1.437 -}
1.438 -
1.439 -/*
1.440 -** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
1.441 -** where X is a reference to the iColumn of table iCur and <op> is one of
1.442 -** the WO_xx operator codes specified by the op parameter.
1.443 -** Return a pointer to the term. Return 0 if not found.
1.444 -*/
1.445 -static WhereTerm *findTerm(
1.446 - WhereClause *pWC, /* The WHERE clause to be searched */
1.447 - int iCur, /* Cursor number of LHS */
1.448 - int iColumn, /* Column number of LHS */
1.449 - Bitmask notReady, /* RHS must not overlap with this mask */
1.450 - u16 op, /* Mask of WO_xx values describing operator */
1.451 - Index *pIdx /* Must be compatible with this index, if not NULL */
1.452 -){
1.453 - WhereTerm *pTerm;
1.454 - int k;
1.455 - for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
1.456 - if( pTerm->leftCursor==iCur
1.457 - && (pTerm->prereqRight & notReady)==0
1.458 - && pTerm->leftColumn==iColumn
1.459 - && (pTerm->eOperator & op)!=0
1.460 - ){
1.461 - if( iCur>=0 && pIdx && pTerm->eOperator!=WO_ISNULL ){
1.462 - Expr *pX = pTerm->pExpr;
1.463 - CollSeq *pColl;
1.464 - char idxaff;
1.465 - int j;
1.466 - Parse *pParse = pWC->pParse;
1.467 -
1.468 - idxaff = pIdx->pTable->aCol[iColumn].affinity;
1.469 - if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
1.470 -
1.471 - /* Figure out the collation sequence required from an index for
1.472 - ** it to be useful for optimising expression pX. Store this
1.473 - ** value in variable pColl.
1.474 - */
1.475 - assert(pX->pLeft);
1.476 - pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
1.477 - if( !pColl ){
1.478 - pColl = pParse->db->pDfltColl;
1.479 - }
1.480 -
1.481 - for(j=0; j<pIdx->nColumn && pIdx->aiColumn[j]!=iColumn; j++){}
1.482 - assert( j<pIdx->nColumn );
1.483 - if( sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
1.484 - }
1.485 - return pTerm;
1.486 - }
1.487 - }
1.488 - return 0;
1.489 -}
1.490 -
1.491 -/* Forward reference */
1.492 -static void exprAnalyze(SrcList*, WhereClause*, int);
1.493 -
1.494 -/*
1.495 -** Call exprAnalyze on all terms in a WHERE clause.
1.496 -**
1.497 -**
1.498 -*/
1.499 -static void exprAnalyzeAll(
1.500 - SrcList *pTabList, /* the FROM clause */
1.501 - WhereClause *pWC /* the WHERE clause to be analyzed */
1.502 -){
1.503 - int i;
1.504 - for(i=pWC->nTerm-1; i>=0; i--){
1.505 - exprAnalyze(pTabList, pWC, i);
1.506 - }
1.507 -}
1.508 -
1.509 -#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
1.510 -/*
1.511 -** Check to see if the given expression is a LIKE or GLOB operator that
1.512 -** can be optimized using inequality constraints. Return TRUE if it is
1.513 -** so and false if not.
1.514 -**
1.515 -** In order for the operator to be optimizible, the RHS must be a string
1.516 -** literal that does not begin with a wildcard.
1.517 -*/
1.518 -static int isLikeOrGlob(
1.519 - sqlite3 *db, /* The database */
1.520 - Expr *pExpr, /* Test this expression */
1.521 - int *pnPattern, /* Number of non-wildcard prefix characters */
1.522 - int *pisComplete /* True if the only wildcard is % in the last character */
1.523 -){
1.524 - const char *z;
1.525 - Expr *pRight, *pLeft;
1.526 - ExprList *pList;
1.527 - int c, cnt;
1.528 - int noCase;
1.529 - char wc[3];
1.530 - CollSeq *pColl;
1.531 -
1.532 - if( !sqlite3IsLikeFunction(db, pExpr, &noCase, wc) ){
1.533 - return 0;
1.534 - }
1.535 - pList = pExpr->pList;
1.536 - pRight = pList->a[0].pExpr;
1.537 - if( pRight->op!=TK_STRING ){
1.538 - return 0;
1.539 - }
1.540 - pLeft = pList->a[1].pExpr;
1.541 - if( pLeft->op!=TK_COLUMN ){
1.542 - return 0;
1.543 - }
1.544 - pColl = pLeft->pColl;
1.545 - if( pColl==0 ){
1.546 - /* TODO: Coverage testing doesn't get this case. Is it actually possible
1.547 - ** for an expression of type TK_COLUMN to not have an assigned collation
1.548 - ** sequence at this point?
1.549 - */
1.550 - pColl = db->pDfltColl;
1.551 - }
1.552 - if( (pColl->type!=SQLITE_COLL_BINARY || noCase) &&
1.553 - (pColl->type!=SQLITE_COLL_NOCASE || !noCase) ){
1.554 - return 0;
1.555 - }
1.556 - sqlite3DequoteExpr(db, pRight);
1.557 - z = (char *)pRight->token.z;
1.558 - for(cnt=0; (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2]; cnt++){}
1.559 - if( cnt==0 || 255==(u8)z[cnt] ){
1.560 - return 0;
1.561 - }
1.562 - *pisComplete = z[cnt]==wc[0] && z[cnt+1]==0;
1.563 - *pnPattern = cnt;
1.564 - return 1;
1.565 -}
1.566 -#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
1.567 -
1.568 -
1.569 -#ifndef SQLITE_OMIT_VIRTUALTABLE
1.570 -/*
1.571 -** Check to see if the given expression is of the form
1.572 -**
1.573 -** column MATCH expr
1.574 -**
1.575 -** If it is then return TRUE. If not, return FALSE.
1.576 -*/
1.577 -static int isMatchOfColumn(
1.578 - Expr *pExpr /* Test this expression */
1.579 -){
1.580 - ExprList *pList;
1.581 -
1.582 - if( pExpr->op!=TK_FUNCTION ){
1.583 - return 0;
1.584 - }
1.585 - if( pExpr->token.n!=5 ||
1.586 - sqlite3StrNICmp((const char*)pExpr->token.z,"match",5)!=0 ){
1.587 - return 0;
1.588 - }
1.589 - pList = pExpr->pList;
1.590 - if( pList->nExpr!=2 ){
1.591 - return 0;
1.592 - }
1.593 - if( pList->a[1].pExpr->op != TK_COLUMN ){
1.594 - return 0;
1.595 - }
1.596 - return 1;
1.597 -}
1.598 -#endif /* SQLITE_OMIT_VIRTUALTABLE */
1.599 -
1.600 -/*
1.601 -** If the pBase expression originated in the ON or USING clause of
1.602 -** a join, then transfer the appropriate markings over to derived.
1.603 -*/
1.604 -static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
1.605 - pDerived->flags |= pBase->flags & EP_FromJoin;
1.606 - pDerived->iRightJoinTable = pBase->iRightJoinTable;
1.607 -}
1.608 -
1.609 -#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
1.610 -/*
1.611 -** Return TRUE if the given term of an OR clause can be converted
1.612 -** into an IN clause. The iCursor and iColumn define the left-hand
1.613 -** side of the IN clause.
1.614 -**
1.615 -** The context is that we have multiple OR-connected equality terms
1.616 -** like this:
1.617 -**
1.618 -** a=<expr1> OR a=<expr2> OR b=<expr3> OR ...
1.619 -**
1.620 -** The pOrTerm input to this routine corresponds to a single term of
1.621 -** this OR clause. In order for the term to be a condidate for
1.622 -** conversion to an IN operator, the following must be true:
1.623 -**
1.624 -** * The left-hand side of the term must be the column which
1.625 -** is identified by iCursor and iColumn.
1.626 -**
1.627 -** * If the right-hand side is also a column, then the affinities
1.628 -** of both right and left sides must be such that no type
1.629 -** conversions are required on the right. (Ticket #2249)
1.630 -**
1.631 -** If both of these conditions are true, then return true. Otherwise
1.632 -** return false.
1.633 -*/
1.634 -static int orTermIsOptCandidate(WhereTerm *pOrTerm, int iCursor, int iColumn){
1.635 - int affLeft, affRight;
1.636 - assert( pOrTerm->eOperator==WO_EQ );
1.637 - if( pOrTerm->leftCursor!=iCursor ){
1.638 - return 0;
1.639 - }
1.640 - if( pOrTerm->leftColumn!=iColumn ){
1.641 - return 0;
1.642 - }
1.643 - affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
1.644 - if( affRight==0 ){
1.645 - return 1;
1.646 - }
1.647 - affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
1.648 - if( affRight!=affLeft ){
1.649 - return 0;
1.650 - }
1.651 - return 1;
1.652 -}
1.653 -
1.654 -/*
1.655 -** Return true if the given term of an OR clause can be ignored during
1.656 -** a check to make sure all OR terms are candidates for optimization.
1.657 -** In other words, return true if a call to the orTermIsOptCandidate()
1.658 -** above returned false but it is not necessary to disqualify the
1.659 -** optimization.
1.660 -**
1.661 -** Suppose the original OR phrase was this:
1.662 -**
1.663 -** a=4 OR a=11 OR a=b
1.664 -**
1.665 -** During analysis, the third term gets flipped around and duplicate
1.666 -** so that we are left with this:
1.667 -**
1.668 -** a=4 OR a=11 OR a=b OR b=a
1.669 -**
1.670 -** Since the last two terms are duplicates, only one of them
1.671 -** has to qualify in order for the whole phrase to qualify. When
1.672 -** this routine is called, we know that pOrTerm did not qualify.
1.673 -** This routine merely checks to see if pOrTerm has a duplicate that
1.674 -** might qualify. If there is a duplicate that has not yet been
1.675 -** disqualified, then return true. If there are no duplicates, or
1.676 -** the duplicate has also been disqualifed, return false.
1.677 -*/
1.678 -static int orTermHasOkDuplicate(WhereClause *pOr, WhereTerm *pOrTerm){
1.679 - if( pOrTerm->flags & TERM_COPIED ){
1.680 - /* This is the original term. The duplicate is to the left had
1.681 - ** has not yet been analyzed and thus has not yet been disqualified. */
1.682 - return 1;
1.683 - }
1.684 - if( (pOrTerm->flags & TERM_VIRTUAL)!=0
1.685 - && (pOr->a[pOrTerm->iParent].flags & TERM_OR_OK)!=0 ){
1.686 - /* This is a duplicate term. The original qualified so this one
1.687 - ** does not have to. */
1.688 - return 1;
1.689 - }
1.690 - /* This is either a singleton term or else it is a duplicate for
1.691 - ** which the original did not qualify. Either way we are done for. */
1.692 - return 0;
1.693 -}
1.694 -#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
1.695 -
1.696 -/*
1.697 -** The input to this routine is an WhereTerm structure with only the
1.698 -** "pExpr" field filled in. The job of this routine is to analyze the
1.699 -** subexpression and populate all the other fields of the WhereTerm
1.700 -** structure.
1.701 -**
1.702 -** If the expression is of the form "<expr> <op> X" it gets commuted
1.703 -** to the standard form of "X <op> <expr>". If the expression is of
1.704 -** the form "X <op> Y" where both X and Y are columns, then the original
1.705 -** expression is unchanged and a new virtual expression of the form
1.706 -** "Y <op> X" is added to the WHERE clause and analyzed separately.
1.707 -*/
1.708 -static void exprAnalyze(
1.709 - SrcList *pSrc, /* the FROM clause */
1.710 - WhereClause *pWC, /* the WHERE clause */
1.711 - int idxTerm /* Index of the term to be analyzed */
1.712 -){
1.713 - WhereTerm *pTerm = &pWC->a[idxTerm];
1.714 - ExprMaskSet *pMaskSet = pWC->pMaskSet;
1.715 - Expr *pExpr = pTerm->pExpr;
1.716 - Bitmask prereqLeft;
1.717 - Bitmask prereqAll;
1.718 - int nPattern;
1.719 - int isComplete;
1.720 - int op;
1.721 - Parse *pParse = pWC->pParse;
1.722 - sqlite3 *db = pParse->db;
1.723 -
1.724 - if( db->mallocFailed ) return;
1.725 - prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
1.726 - op = pExpr->op;
1.727 - if( op==TK_IN ){
1.728 - assert( pExpr->pRight==0 );
1.729 - pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->pList)
1.730 - | exprSelectTableUsage(pMaskSet, pExpr->pSelect);
1.731 - }else if( op==TK_ISNULL ){
1.732 - pTerm->prereqRight = 0;
1.733 - }else{
1.734 - pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
1.735 - }
1.736 - prereqAll = exprTableUsage(pMaskSet, pExpr);
1.737 - if( ExprHasProperty(pExpr, EP_FromJoin) ){
1.738 - prereqAll |= getMask(pMaskSet, pExpr->iRightJoinTable);
1.739 - }
1.740 - pTerm->prereqAll = prereqAll;
1.741 - pTerm->leftCursor = -1;
1.742 - pTerm->iParent = -1;
1.743 - pTerm->eOperator = 0;
1.744 - if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){
1.745 - Expr *pLeft = pExpr->pLeft;
1.746 - Expr *pRight = pExpr->pRight;
1.747 - if( pLeft->op==TK_COLUMN ){
1.748 - pTerm->leftCursor = pLeft->iTable;
1.749 - pTerm->leftColumn = pLeft->iColumn;
1.750 - pTerm->eOperator = operatorMask(op);
1.751 - }
1.752 - if( pRight && pRight->op==TK_COLUMN ){
1.753 - WhereTerm *pNew;
1.754 - Expr *pDup;
1.755 - if( pTerm->leftCursor>=0 ){
1.756 - int idxNew;
1.757 - pDup = sqlite3ExprDup(db, pExpr);
1.758 - if( db->mallocFailed ){
1.759 - sqlite3ExprDelete(pDup);
1.760 - return;
1.761 - }
1.762 - idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
1.763 - if( idxNew==0 ) return;
1.764 - pNew = &pWC->a[idxNew];
1.765 - pNew->iParent = idxTerm;
1.766 - pTerm = &pWC->a[idxTerm];
1.767 - pTerm->nChild = 1;
1.768 - pTerm->flags |= TERM_COPIED;
1.769 - }else{
1.770 - pDup = pExpr;
1.771 - pNew = pTerm;
1.772 - }
1.773 - exprCommute(pDup);
1.774 - pLeft = pDup->pLeft;
1.775 - pNew->leftCursor = pLeft->iTable;
1.776 - pNew->leftColumn = pLeft->iColumn;
1.777 - pNew->prereqRight = prereqLeft;
1.778 - pNew->prereqAll = prereqAll;
1.779 - pNew->eOperator = operatorMask(pDup->op);
1.780 - }
1.781 - }
1.782 -
1.783 -#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
1.784 - /* If a term is the BETWEEN operator, create two new virtual terms
1.785 - ** that define the range that the BETWEEN implements.
1.786 - */
1.787 - else if( pExpr->op==TK_BETWEEN ){
1.788 - ExprList *pList = pExpr->pList;
1.789 - int i;
1.790 - static const u8 ops[] = {TK_GE, TK_LE};
1.791 - assert( pList!=0 );
1.792 - assert( pList->nExpr==2 );
1.793 - for(i=0; i<2; i++){
1.794 - Expr *pNewExpr;
1.795 - int idxNew;
1.796 - pNewExpr = sqlite3Expr(db, ops[i], sqlite3ExprDup(db, pExpr->pLeft),
1.797 - sqlite3ExprDup(db, pList->a[i].pExpr), 0);
1.798 - idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
1.799 - exprAnalyze(pSrc, pWC, idxNew);
1.800 - pTerm = &pWC->a[idxTerm];
1.801 - pWC->a[idxNew].iParent = idxTerm;
1.802 - }
1.803 - pTerm->nChild = 2;
1.804 - }
1.805 -#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
1.806 -
1.807 -#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
1.808 - /* Attempt to convert OR-connected terms into an IN operator so that
1.809 - ** they can make use of indices. Example:
1.810 - **
1.811 - ** x = expr1 OR expr2 = x OR x = expr3
1.812 - **
1.813 - ** is converted into
1.814 - **
1.815 - ** x IN (expr1,expr2,expr3)
1.816 - **
1.817 - ** This optimization must be omitted if OMIT_SUBQUERY is defined because
1.818 - ** the compiler for the the IN operator is part of sub-queries.
1.819 - */
1.820 - else if( pExpr->op==TK_OR ){
1.821 - int ok;
1.822 - int i, j;
1.823 - int iColumn, iCursor;
1.824 - WhereClause sOr;
1.825 - WhereTerm *pOrTerm;
1.826 -
1.827 - assert( (pTerm->flags & TERM_DYNAMIC)==0 );
1.828 - whereClauseInit(&sOr, pWC->pParse, pMaskSet);
1.829 - whereSplit(&sOr, pExpr, TK_OR);
1.830 - exprAnalyzeAll(pSrc, &sOr);
1.831 - assert( sOr.nTerm>=2 );
1.832 - j = 0;
1.833 - do{
1.834 - assert( j<sOr.nTerm );
1.835 - iColumn = sOr.a[j].leftColumn;
1.836 - iCursor = sOr.a[j].leftCursor;
1.837 - ok = iCursor>=0;
1.838 - for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
1.839 - if( pOrTerm->eOperator!=WO_EQ ){
1.840 - goto or_not_possible;
1.841 - }
1.842 - if( orTermIsOptCandidate(pOrTerm, iCursor, iColumn) ){
1.843 - pOrTerm->flags |= TERM_OR_OK;
1.844 - }else if( orTermHasOkDuplicate(&sOr, pOrTerm) ){
1.845 - pOrTerm->flags &= ~TERM_OR_OK;
1.846 - }else{
1.847 - ok = 0;
1.848 - }
1.849 - }
1.850 - }while( !ok && (sOr.a[j++].flags & TERM_COPIED)!=0 && j<2 );
1.851 - if( ok ){
1.852 - ExprList *pList = 0;
1.853 - Expr *pNew, *pDup;
1.854 - Expr *pLeft = 0;
1.855 - for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
1.856 - if( (pOrTerm->flags & TERM_OR_OK)==0 ) continue;
1.857 - pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight);
1.858 - pList = sqlite3ExprListAppend(pWC->pParse, pList, pDup, 0);
1.859 - pLeft = pOrTerm->pExpr->pLeft;
1.860 - }
1.861 - assert( pLeft!=0 );
1.862 - pDup = sqlite3ExprDup(db, pLeft);
1.863 - pNew = sqlite3Expr(db, TK_IN, pDup, 0, 0);
1.864 - if( pNew ){
1.865 - int idxNew;
1.866 - transferJoinMarkings(pNew, pExpr);
1.867 - pNew->pList = pList;
1.868 - idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
1.869 - exprAnalyze(pSrc, pWC, idxNew);
1.870 - pTerm = &pWC->a[idxTerm];
1.871 - pWC->a[idxNew].iParent = idxTerm;
1.872 - pTerm->nChild = 1;
1.873 - }else{
1.874 - sqlite3ExprListDelete(pList);
1.875 - }
1.876 - }
1.877 -or_not_possible:
1.878 - whereClauseClear(&sOr);
1.879 - }
1.880 -#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
1.881 -
1.882 -#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
1.883 - /* Add constraints to reduce the search space on a LIKE or GLOB
1.884 - ** operator.
1.885 - */
1.886 - if( isLikeOrGlob(db, pExpr, &nPattern, &isComplete) ){
1.887 - Expr *pLeft, *pRight;
1.888 - Expr *pStr1, *pStr2;
1.889 - Expr *pNewExpr1, *pNewExpr2;
1.890 - int idxNew1, idxNew2;
1.891 -
1.892 - pLeft = pExpr->pList->a[1].pExpr;
1.893 - pRight = pExpr->pList->a[0].pExpr;
1.894 - pStr1 = sqlite3PExpr(pParse, TK_STRING, 0, 0, 0);
1.895 - if( pStr1 ){
1.896 - sqlite3TokenCopy(db, &pStr1->token, &pRight->token);
1.897 - pStr1->token.n = nPattern;
1.898 - pStr1->flags = EP_Dequoted;
1.899 - }
1.900 - pStr2 = sqlite3ExprDup(db, pStr1);
1.901 - if( pStr2 ){
1.902 - assert( pStr2->token.dyn );
1.903 - ++*(u8*)&pStr2->token.z[nPattern-1];
1.904 - }
1.905 - pNewExpr1 = sqlite3PExpr(pParse, TK_GE, sqlite3ExprDup(db,pLeft), pStr1, 0);
1.906 - idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
1.907 - exprAnalyze(pSrc, pWC, idxNew1);
1.908 - pNewExpr2 = sqlite3PExpr(pParse, TK_LT, sqlite3ExprDup(db,pLeft), pStr2, 0);
1.909 - idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
1.910 - exprAnalyze(pSrc, pWC, idxNew2);
1.911 - pTerm = &pWC->a[idxTerm];
1.912 - if( isComplete ){
1.913 - pWC->a[idxNew1].iParent = idxTerm;
1.914 - pWC->a[idxNew2].iParent = idxTerm;
1.915 - pTerm->nChild = 2;
1.916 - }
1.917 - }
1.918 -#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
1.919 -
1.920 -#ifndef SQLITE_OMIT_VIRTUALTABLE
1.921 - /* Add a WO_MATCH auxiliary term to the constraint set if the
1.922 - ** current expression is of the form: column MATCH expr.
1.923 - ** This information is used by the xBestIndex methods of
1.924 - ** virtual tables. The native query optimizer does not attempt
1.925 - ** to do anything with MATCH functions.
1.926 - */
1.927 - if( isMatchOfColumn(pExpr) ){
1.928 - int idxNew;
1.929 - Expr *pRight, *pLeft;
1.930 - WhereTerm *pNewTerm;
1.931 - Bitmask prereqColumn, prereqExpr;
1.932 -
1.933 - pRight = pExpr->pList->a[0].pExpr;
1.934 - pLeft = pExpr->pList->a[1].pExpr;
1.935 - prereqExpr = exprTableUsage(pMaskSet, pRight);
1.936 - prereqColumn = exprTableUsage(pMaskSet, pLeft);
1.937 - if( (prereqExpr & prereqColumn)==0 ){
1.938 - Expr *pNewExpr;
1.939 - pNewExpr = sqlite3Expr(db, TK_MATCH, 0, sqlite3ExprDup(db, pRight), 0);
1.940 - idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
1.941 - pNewTerm = &pWC->a[idxNew];
1.942 - pNewTerm->prereqRight = prereqExpr;
1.943 - pNewTerm->leftCursor = pLeft->iTable;
1.944 - pNewTerm->leftColumn = pLeft->iColumn;
1.945 - pNewTerm->eOperator = WO_MATCH;
1.946 - pNewTerm->iParent = idxTerm;
1.947 - pTerm = &pWC->a[idxTerm];
1.948 - pTerm->nChild = 1;
1.949 - pTerm->flags |= TERM_COPIED;
1.950 - pNewTerm->prereqAll = pTerm->prereqAll;
1.951 - }
1.952 - }
1.953 -#endif /* SQLITE_OMIT_VIRTUALTABLE */
1.954 -}
1.955 -
1.956 -/*
1.957 -** Return TRUE if any of the expressions in pList->a[iFirst...] contain
1.958 -** a reference to any table other than the iBase table.
1.959 -*/
1.960 -static int referencesOtherTables(
1.961 - ExprList *pList, /* Search expressions in ths list */
1.962 - ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
1.963 - int iFirst, /* Be searching with the iFirst-th expression */
1.964 - int iBase /* Ignore references to this table */
1.965 -){
1.966 - Bitmask allowed = ~getMask(pMaskSet, iBase);
1.967 - while( iFirst<pList->nExpr ){
1.968 - if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){
1.969 - return 1;
1.970 - }
1.971 - }
1.972 - return 0;
1.973 -}
1.974 -
1.975 -
1.976 -/*
1.977 -** This routine decides if pIdx can be used to satisfy the ORDER BY
1.978 -** clause. If it can, it returns 1. If pIdx cannot satisfy the
1.979 -** ORDER BY clause, this routine returns 0.
1.980 -**
1.981 -** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the
1.982 -** left-most table in the FROM clause of that same SELECT statement and
1.983 -** the table has a cursor number of "base". pIdx is an index on pTab.
1.984 -**
1.985 -** nEqCol is the number of columns of pIdx that are used as equality
1.986 -** constraints. Any of these columns may be missing from the ORDER BY
1.987 -** clause and the match can still be a success.
1.988 -**
1.989 -** All terms of the ORDER BY that match against the index must be either
1.990 -** ASC or DESC. (Terms of the ORDER BY clause past the end of a UNIQUE
1.991 -** index do not need to satisfy this constraint.) The *pbRev value is
1.992 -** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
1.993 -** the ORDER BY clause is all ASC.
1.994 -*/
1.995 -static int isSortingIndex(
1.996 - Parse *pParse, /* Parsing context */
1.997 - ExprMaskSet *pMaskSet, /* Mapping from table indices to bitmaps */
1.998 - Index *pIdx, /* The index we are testing */
1.999 - int base, /* Cursor number for the table to be sorted */
1.1000 - ExprList *pOrderBy, /* The ORDER BY clause */
1.1001 - int nEqCol, /* Number of index columns with == constraints */
1.1002 - int *pbRev /* Set to 1 if ORDER BY is DESC */
1.1003 -){
1.1004 - int i, j; /* Loop counters */
1.1005 - int sortOrder = 0; /* XOR of index and ORDER BY sort direction */
1.1006 - int nTerm; /* Number of ORDER BY terms */
1.1007 - struct ExprList_item *pTerm; /* A term of the ORDER BY clause */
1.1008 - sqlite3 *db = pParse->db;
1.1009 -
1.1010 - assert( pOrderBy!=0 );
1.1011 - nTerm = pOrderBy->nExpr;
1.1012 - assert( nTerm>0 );
1.1013 -
1.1014 - /* Match terms of the ORDER BY clause against columns of
1.1015 - ** the index.
1.1016 - **
1.1017 - ** Note that indices have pIdx->nColumn regular columns plus
1.1018 - ** one additional column containing the rowid. The rowid column
1.1019 - ** of the index is also allowed to match against the ORDER BY
1.1020 - ** clause.
1.1021 - */
1.1022 - for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<=pIdx->nColumn; i++){
1.1023 - Expr *pExpr; /* The expression of the ORDER BY pTerm */
1.1024 - CollSeq *pColl; /* The collating sequence of pExpr */
1.1025 - int termSortOrder; /* Sort order for this term */
1.1026 - int iColumn; /* The i-th column of the index. -1 for rowid */
1.1027 - int iSortOrder; /* 1 for DESC, 0 for ASC on the i-th index term */
1.1028 - const char *zColl; /* Name of the collating sequence for i-th index term */
1.1029 -
1.1030 - pExpr = pTerm->pExpr;
1.1031 - if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
1.1032 - /* Can not use an index sort on anything that is not a column in the
1.1033 - ** left-most table of the FROM clause */
1.1034 - break;
1.1035 - }
1.1036 - pColl = sqlite3ExprCollSeq(pParse, pExpr);
1.1037 - if( !pColl ){
1.1038 - pColl = db->pDfltColl;
1.1039 - }
1.1040 - if( i<pIdx->nColumn ){
1.1041 - iColumn = pIdx->aiColumn[i];
1.1042 - if( iColumn==pIdx->pTable->iPKey ){
1.1043 - iColumn = -1;
1.1044 - }
1.1045 - iSortOrder = pIdx->aSortOrder[i];
1.1046 - zColl = pIdx->azColl[i];
1.1047 - }else{
1.1048 - iColumn = -1;
1.1049 - iSortOrder = 0;
1.1050 - zColl = pColl->zName;
1.1051 - }
1.1052 - if( pExpr->iColumn!=iColumn || sqlite3StrICmp(pColl->zName, zColl) ){
1.1053 - /* Term j of the ORDER BY clause does not match column i of the index */
1.1054 - if( i<nEqCol ){
1.1055 - /* If an index column that is constrained by == fails to match an
1.1056 - ** ORDER BY term, that is OK. Just ignore that column of the index
1.1057 - */
1.1058 - continue;
1.1059 - }else{
1.1060 - /* If an index column fails to match and is not constrained by ==
1.1061 - ** then the index cannot satisfy the ORDER BY constraint.
1.1062 - */
1.1063 - return 0;
1.1064 - }
1.1065 - }
1.1066 - assert( pIdx->aSortOrder!=0 );
1.1067 - assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 );
1.1068 - assert( iSortOrder==0 || iSortOrder==1 );
1.1069 - termSortOrder = iSortOrder ^ pTerm->sortOrder;
1.1070 - if( i>nEqCol ){
1.1071 - if( termSortOrder!=sortOrder ){
1.1072 - /* Indices can only be used if all ORDER BY terms past the
1.1073 - ** equality constraints are all either DESC or ASC. */
1.1074 - return 0;
1.1075 - }
1.1076 - }else{
1.1077 - sortOrder = termSortOrder;
1.1078 - }
1.1079 - j++;
1.1080 - pTerm++;
1.1081 - if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
1.1082 - /* If the indexed column is the primary key and everything matches
1.1083 - ** so far and none of the ORDER BY terms to the right reference other
1.1084 - ** tables in the join, then we are assured that the index can be used
1.1085 - ** to sort because the primary key is unique and so none of the other
1.1086 - ** columns will make any difference
1.1087 - */
1.1088 - j = nTerm;
1.1089 - }
1.1090 - }
1.1091 -
1.1092 - *pbRev = sortOrder!=0;
1.1093 - if( j>=nTerm ){
1.1094 - /* All terms of the ORDER BY clause are covered by this index so
1.1095 - ** this index can be used for sorting. */
1.1096 - return 1;
1.1097 - }
1.1098 - if( pIdx->onError!=OE_None && i==pIdx->nColumn
1.1099 - && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
1.1100 - /* All terms of this index match some prefix of the ORDER BY clause
1.1101 - ** and the index is UNIQUE and no terms on the tail of the ORDER BY
1.1102 - ** clause reference other tables in a join. If this is all true then
1.1103 - ** the order by clause is superfluous. */
1.1104 - return 1;
1.1105 - }
1.1106 - return 0;
1.1107 -}
1.1108 -
1.1109 -/*
1.1110 -** Check table to see if the ORDER BY clause in pOrderBy can be satisfied
1.1111 -** by sorting in order of ROWID. Return true if so and set *pbRev to be
1.1112 -** true for reverse ROWID and false for forward ROWID order.
1.1113 -*/
1.1114 -static int sortableByRowid(
1.1115 - int base, /* Cursor number for table to be sorted */
1.1116 - ExprList *pOrderBy, /* The ORDER BY clause */
1.1117 - ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
1.1118 - int *pbRev /* Set to 1 if ORDER BY is DESC */
1.1119 -){
1.1120 - Expr *p;
1.1121 -
1.1122 - assert( pOrderBy!=0 );
1.1123 - assert( pOrderBy->nExpr>0 );
1.1124 - p = pOrderBy->a[0].pExpr;
1.1125 - if( p->op==TK_COLUMN && p->iTable==base && p->iColumn==-1
1.1126 - && !referencesOtherTables(pOrderBy, pMaskSet, 1, base) ){
1.1127 - *pbRev = pOrderBy->a[0].sortOrder;
1.1128 - return 1;
1.1129 - }
1.1130 - return 0;
1.1131 -}
1.1132 -
1.1133 -/*
1.1134 -** Prepare a crude estimate of the logarithm of the input value.
1.1135 -** The results need not be exact. This is only used for estimating
1.1136 -** the total cost of performing operatings with O(logN) or O(NlogN)
1.1137 -** complexity. Because N is just a guess, it is no great tragedy if
1.1138 -** logN is a little off.
1.1139 -*/
1.1140 -static double estLog(double N){
1.1141 - double logN = 1;
1.1142 - double x = 10;
1.1143 - while( N>x ){
1.1144 - logN += 1;
1.1145 - x *= 10;
1.1146 - }
1.1147 - return logN;
1.1148 -}
1.1149 -
1.1150 -/*
1.1151 -** Two routines for printing the content of an sqlite3_index_info
1.1152 -** structure. Used for testing and debugging only. If neither
1.1153 -** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
1.1154 -** are no-ops.
1.1155 -*/
1.1156 -#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_DEBUG)
1.1157 -static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
1.1158 - int i;
1.1159 - if( !sqlite3_where_trace ) return;
1.1160 - for(i=0; i<p->nConstraint; i++){
1.1161 - sqlite3DebugPrintf(" constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
1.1162 - i,
1.1163 - p->aConstraint[i].iColumn,
1.1164 - p->aConstraint[i].iTermOffset,
1.1165 - p->aConstraint[i].op,
1.1166 - p->aConstraint[i].usable);
1.1167 - }
1.1168 - for(i=0; i<p->nOrderBy; i++){
1.1169 - sqlite3DebugPrintf(" orderby[%d]: col=%d desc=%d\n",
1.1170 - i,
1.1171 - p->aOrderBy[i].iColumn,
1.1172 - p->aOrderBy[i].desc);
1.1173 - }
1.1174 -}
1.1175 -static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
1.1176 - int i;
1.1177 - if( !sqlite3_where_trace ) return;
1.1178 - for(i=0; i<p->nConstraint; i++){
1.1179 - sqlite3DebugPrintf(" usage[%d]: argvIdx=%d omit=%d\n",
1.1180 - i,
1.1181 - p->aConstraintUsage[i].argvIndex,
1.1182 - p->aConstraintUsage[i].omit);
1.1183 - }
1.1184 - sqlite3DebugPrintf(" idxNum=%d\n", p->idxNum);
1.1185 - sqlite3DebugPrintf(" idxStr=%s\n", p->idxStr);
1.1186 - sqlite3DebugPrintf(" orderByConsumed=%d\n", p->orderByConsumed);
1.1187 - sqlite3DebugPrintf(" estimatedCost=%g\n", p->estimatedCost);
1.1188 -}
1.1189 -#else
1.1190 -#define TRACE_IDX_INPUTS(A)
1.1191 -#define TRACE_IDX_OUTPUTS(A)
1.1192 -#endif
1.1193 -
1.1194 -#ifndef SQLITE_OMIT_VIRTUALTABLE
1.1195 -/*
1.1196 -** Compute the best index for a virtual table.
1.1197 -**
1.1198 -** The best index is computed by the xBestIndex method of the virtual
1.1199 -** table module. This routine is really just a wrapper that sets up
1.1200 -** the sqlite3_index_info structure that is used to communicate with
1.1201 -** xBestIndex.
1.1202 -**
1.1203 -** In a join, this routine might be called multiple times for the
1.1204 -** same virtual table. The sqlite3_index_info structure is created
1.1205 -** and initialized on the first invocation and reused on all subsequent
1.1206 -** invocations. The sqlite3_index_info structure is also used when
1.1207 -** code is generated to access the virtual table. The whereInfoDelete()
1.1208 -** routine takes care of freeing the sqlite3_index_info structure after
1.1209 -** everybody has finished with it.
1.1210 -*/
1.1211 -static double bestVirtualIndex(
1.1212 - Parse *pParse, /* The parsing context */
1.1213 - WhereClause *pWC, /* The WHERE clause */
1.1214 - struct SrcList_item *pSrc, /* The FROM clause term to search */
1.1215 - Bitmask notReady, /* Mask of cursors that are not available */
1.1216 - ExprList *pOrderBy, /* The order by clause */
1.1217 - int orderByUsable, /* True if we can potential sort */
1.1218 - sqlite3_index_info **ppIdxInfo /* Index information passed to xBestIndex */
1.1219 -){
1.1220 - Table *pTab = pSrc->pTab;
1.1221 - sqlite3_index_info *pIdxInfo;
1.1222 - struct sqlite3_index_constraint *pIdxCons;
1.1223 - struct sqlite3_index_orderby *pIdxOrderBy;
1.1224 - struct sqlite3_index_constraint_usage *pUsage;
1.1225 - WhereTerm *pTerm;
1.1226 - int i, j;
1.1227 - int nOrderBy;
1.1228 - int rc;
1.1229 -
1.1230 - /* If the sqlite3_index_info structure has not been previously
1.1231 - ** allocated and initialized for this virtual table, then allocate
1.1232 - ** and initialize it now
1.1233 - */
1.1234 - pIdxInfo = *ppIdxInfo;
1.1235 - if( pIdxInfo==0 ){
1.1236 - WhereTerm *pTerm;
1.1237 - int nTerm;
1.1238 - WHERETRACE(("Recomputing index info for %s...\n", pTab->zName));
1.1239 -
1.1240 - /* Count the number of possible WHERE clause constraints referring
1.1241 - ** to this virtual table */
1.1242 - for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
1.1243 - if( pTerm->leftCursor != pSrc->iCursor ) continue;
1.1244 - if( pTerm->eOperator==WO_IN ) continue;
1.1245 - nTerm++;
1.1246 - }
1.1247 -
1.1248 - /* If the ORDER BY clause contains only columns in the current
1.1249 - ** virtual table then allocate space for the aOrderBy part of
1.1250 - ** the sqlite3_index_info structure.
1.1251 - */
1.1252 - nOrderBy = 0;
1.1253 - if( pOrderBy ){
1.1254 - for(i=0; i<pOrderBy->nExpr; i++){
1.1255 - Expr *pExpr = pOrderBy->a[i].pExpr;
1.1256 - if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
1.1257 - }
1.1258 - if( i==pOrderBy->nExpr ){
1.1259 - nOrderBy = pOrderBy->nExpr;
1.1260 - }
1.1261 - }
1.1262 -
1.1263 - /* Allocate the sqlite3_index_info structure
1.1264 - */
1.1265 - pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
1.1266 - + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
1.1267 - + sizeof(*pIdxOrderBy)*nOrderBy );
1.1268 - if( pIdxInfo==0 ){
1.1269 - sqlite3ErrorMsg(pParse, "out of memory");
1.1270 - return 0.0;
1.1271 - }
1.1272 - *ppIdxInfo = pIdxInfo;
1.1273 -
1.1274 - /* Initialize the structure. The sqlite3_index_info structure contains
1.1275 - ** many fields that are declared "const" to prevent xBestIndex from
1.1276 - ** changing them. We have to do some funky casting in order to
1.1277 - ** initialize those fields.
1.1278 - */
1.1279 - pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
1.1280 - pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
1.1281 - pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
1.1282 - *(int*)&pIdxInfo->nConstraint = nTerm;
1.1283 - *(int*)&pIdxInfo->nOrderBy = nOrderBy;
1.1284 - *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
1.1285 - *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
1.1286 - *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
1.1287 - pUsage;
1.1288 -
1.1289 - for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
1.1290 - if( pTerm->leftCursor != pSrc->iCursor ) continue;
1.1291 - if( pTerm->eOperator==WO_IN ) continue;
1.1292 - pIdxCons[j].iColumn = pTerm->leftColumn;
1.1293 - pIdxCons[j].iTermOffset = i;
1.1294 - pIdxCons[j].op = pTerm->eOperator;
1.1295 - /* The direct assignment in the previous line is possible only because
1.1296 - ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical. The
1.1297 - ** following asserts verify this fact. */
1.1298 - assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
1.1299 - assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
1.1300 - assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
1.1301 - assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
1.1302 - assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
1.1303 - assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
1.1304 - assert( pTerm->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
1.1305 - j++;
1.1306 - }
1.1307 - for(i=0; i<nOrderBy; i++){
1.1308 - Expr *pExpr = pOrderBy->a[i].pExpr;
1.1309 - pIdxOrderBy[i].iColumn = pExpr->iColumn;
1.1310 - pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
1.1311 - }
1.1312 - }
1.1313 -
1.1314 - /* At this point, the sqlite3_index_info structure that pIdxInfo points
1.1315 - ** to will have been initialized, either during the current invocation or
1.1316 - ** during some prior invocation. Now we just have to customize the
1.1317 - ** details of pIdxInfo for the current invocation and pass it to
1.1318 - ** xBestIndex.
1.1319 - */
1.1320 -
1.1321 - /* The module name must be defined. Also, by this point there must
1.1322 - ** be a pointer to an sqlite3_vtab structure. Otherwise
1.1323 - ** sqlite3ViewGetColumnNames() would have picked up the error.
1.1324 - */
1.1325 - assert( pTab->azModuleArg && pTab->azModuleArg[0] );
1.1326 - assert( pTab->pVtab );
1.1327 -#if 0
1.1328 - if( pTab->pVtab==0 ){
1.1329 - sqlite3ErrorMsg(pParse, "undefined module %s for table %s",
1.1330 - pTab->azModuleArg[0], pTab->zName);
1.1331 - return 0.0;
1.1332 - }
1.1333 -#endif
1.1334 -
1.1335 - /* Set the aConstraint[].usable fields and initialize all
1.1336 - ** output variables to zero.
1.1337 - **
1.1338 - ** aConstraint[].usable is true for constraints where the right-hand
1.1339 - ** side contains only references to tables to the left of the current
1.1340 - ** table. In other words, if the constraint is of the form:
1.1341 - **
1.1342 - ** column = expr
1.1343 - **
1.1344 - ** and we are evaluating a join, then the constraint on column is
1.1345 - ** only valid if all tables referenced in expr occur to the left
1.1346 - ** of the table containing column.
1.1347 - **
1.1348 - ** The aConstraints[] array contains entries for all constraints
1.1349 - ** on the current table. That way we only have to compute it once
1.1350 - ** even though we might try to pick the best index multiple times.
1.1351 - ** For each attempt at picking an index, the order of tables in the
1.1352 - ** join might be different so we have to recompute the usable flag
1.1353 - ** each time.
1.1354 - */
1.1355 - pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
1.1356 - pUsage = pIdxInfo->aConstraintUsage;
1.1357 - for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
1.1358 - j = pIdxCons->iTermOffset;
1.1359 - pTerm = &pWC->a[j];
1.1360 - pIdxCons->usable = (pTerm->prereqRight & notReady)==0;
1.1361 - }
1.1362 - memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
1.1363 - if( pIdxInfo->needToFreeIdxStr ){
1.1364 - sqlite3_free(pIdxInfo->idxStr);
1.1365 - }
1.1366 - pIdxInfo->idxStr = 0;
1.1367 - pIdxInfo->idxNum = 0;
1.1368 - pIdxInfo->needToFreeIdxStr = 0;
1.1369 - pIdxInfo->orderByConsumed = 0;
1.1370 - pIdxInfo->estimatedCost = SQLITE_BIG_DBL / 2.0;
1.1371 - nOrderBy = pIdxInfo->nOrderBy;
1.1372 - if( pIdxInfo->nOrderBy && !orderByUsable ){
1.1373 - *(int*)&pIdxInfo->nOrderBy = 0;
1.1374 - }
1.1375 -
1.1376 - sqlite3SafetyOff(pParse->db);
1.1377 - WHERETRACE(("xBestIndex for %s\n", pTab->zName));
1.1378 - TRACE_IDX_INPUTS(pIdxInfo);
1.1379 - rc = pTab->pVtab->pModule->xBestIndex(pTab->pVtab, pIdxInfo);
1.1380 - TRACE_IDX_OUTPUTS(pIdxInfo);
1.1381 - if( rc!=SQLITE_OK ){
1.1382 - if( rc==SQLITE_NOMEM ){
1.1383 - pParse->db->mallocFailed = 1;
1.1384 - }else {
1.1385 - sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
1.1386 - }
1.1387 - sqlite3SafetyOn(pParse->db);
1.1388 - }else{
1.1389 - rc = sqlite3SafetyOn(pParse->db);
1.1390 - }
1.1391 - *(int*)&pIdxInfo->nOrderBy = nOrderBy;
1.1392 -
1.1393 - return pIdxInfo->estimatedCost;
1.1394 -}
1.1395 -#endif /* SQLITE_OMIT_VIRTUALTABLE */
1.1396 -
1.1397 -/*
1.1398 -** Find the best index for accessing a particular table. Return a pointer
1.1399 -** to the index, flags that describe how the index should be used, the
1.1400 -** number of equality constraints, and the "cost" for this index.
1.1401 -**
1.1402 -** The lowest cost index wins. The cost is an estimate of the amount of
1.1403 -** CPU and disk I/O need to process the request using the selected index.
1.1404 -** Factors that influence cost include:
1.1405 -**
1.1406 -** * The estimated number of rows that will be retrieved. (The
1.1407 -** fewer the better.)
1.1408 -**
1.1409 -** * Whether or not sorting must occur.
1.1410 -**
1.1411 -** * Whether or not there must be separate lookups in the
1.1412 -** index and in the main table.
1.1413 -**
1.1414 -*/
1.1415 -static double bestIndex(
1.1416 - Parse *pParse, /* The parsing context */
1.1417 - WhereClause *pWC, /* The WHERE clause */
1.1418 - struct SrcList_item *pSrc, /* The FROM clause term to search */
1.1419 - Bitmask notReady, /* Mask of cursors that are not available */
1.1420 - ExprList *pOrderBy, /* The order by clause */
1.1421 - Index **ppIndex, /* Make *ppIndex point to the best index */
1.1422 - int *pFlags, /* Put flags describing this choice in *pFlags */
1.1423 - int *pnEq /* Put the number of == or IN constraints here */
1.1424 -){
1.1425 - WhereTerm *pTerm;
1.1426 - Index *bestIdx = 0; /* Index that gives the lowest cost */
1.1427 - double lowestCost; /* The cost of using bestIdx */
1.1428 - int bestFlags = 0; /* Flags associated with bestIdx */
1.1429 - int bestNEq = 0; /* Best value for nEq */
1.1430 - int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */
1.1431 - Index *pProbe; /* An index we are evaluating */
1.1432 - int rev; /* True to scan in reverse order */
1.1433 - int flags; /* Flags associated with pProbe */
1.1434 - int nEq; /* Number of == or IN constraints */
1.1435 - int eqTermMask; /* Mask of valid equality operators */
1.1436 - double cost; /* Cost of using pProbe */
1.1437 -
1.1438 - WHERETRACE(("bestIndex: tbl=%s notReady=%x\n", pSrc->pTab->zName, notReady));
1.1439 - lowestCost = SQLITE_BIG_DBL;
1.1440 - pProbe = pSrc->pTab->pIndex;
1.1441 -
1.1442 - /* If the table has no indices and there are no terms in the where
1.1443 - ** clause that refer to the ROWID, then we will never be able to do
1.1444 - ** anything other than a full table scan on this table. We might as
1.1445 - ** well put it first in the join order. That way, perhaps it can be
1.1446 - ** referenced by other tables in the join.
1.1447 - */
1.1448 - if( pProbe==0 &&
1.1449 - findTerm(pWC, iCur, -1, 0, WO_EQ|WO_IN|WO_LT|WO_LE|WO_GT|WO_GE,0)==0 &&
1.1450 - (pOrderBy==0 || !sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev)) ){
1.1451 - *pFlags = 0;
1.1452 - *ppIndex = 0;
1.1453 - *pnEq = 0;
1.1454 - return 0.0;
1.1455 - }
1.1456 -
1.1457 - /* Check for a rowid=EXPR or rowid IN (...) constraints
1.1458 - */
1.1459 - pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
1.1460 - if( pTerm ){
1.1461 - Expr *pExpr;
1.1462 - *ppIndex = 0;
1.1463 - bestFlags = WHERE_ROWID_EQ;
1.1464 - if( pTerm->eOperator & WO_EQ ){
1.1465 - /* Rowid== is always the best pick. Look no further. Because only
1.1466 - ** a single row is generated, output is always in sorted order */
1.1467 - *pFlags = WHERE_ROWID_EQ | WHERE_UNIQUE;
1.1468 - *pnEq = 1;
1.1469 - WHERETRACE(("... best is rowid\n"));
1.1470 - return 0.0;
1.1471 - }else if( (pExpr = pTerm->pExpr)->pList!=0 ){
1.1472 - /* Rowid IN (LIST): cost is NlogN where N is the number of list
1.1473 - ** elements. */
1.1474 - lowestCost = pExpr->pList->nExpr;
1.1475 - lowestCost *= estLog(lowestCost);
1.1476 - }else{
1.1477 - /* Rowid IN (SELECT): cost is NlogN where N is the number of rows
1.1478 - ** in the result of the inner select. We have no way to estimate
1.1479 - ** that value so make a wild guess. */
1.1480 - lowestCost = 200;
1.1481 - }
1.1482 - WHERETRACE(("... rowid IN cost: %.9g\n", lowestCost));
1.1483 - }
1.1484 -
1.1485 - /* Estimate the cost of a table scan. If we do not know how many
1.1486 - ** entries are in the table, use 1 million as a guess.
1.1487 - */
1.1488 - cost = pProbe ? pProbe->aiRowEst[0] : 1000000;
1.1489 - WHERETRACE(("... table scan base cost: %.9g\n", cost));
1.1490 - flags = WHERE_ROWID_RANGE;
1.1491 -
1.1492 - /* Check for constraints on a range of rowids in a table scan.
1.1493 - */
1.1494 - pTerm = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE|WO_GT|WO_GE, 0);
1.1495 - if( pTerm ){
1.1496 - if( findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0) ){
1.1497 - flags |= WHERE_TOP_LIMIT;
1.1498 - cost /= 3; /* Guess that rowid<EXPR eliminates two-thirds or rows */
1.1499 - }
1.1500 - if( findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0) ){
1.1501 - flags |= WHERE_BTM_LIMIT;
1.1502 - cost /= 3; /* Guess that rowid>EXPR eliminates two-thirds of rows */
1.1503 - }
1.1504 - WHERETRACE(("... rowid range reduces cost to %.9g\n", cost));
1.1505 - }else{
1.1506 - flags = 0;
1.1507 - }
1.1508 -
1.1509 - /* If the table scan does not satisfy the ORDER BY clause, increase
1.1510 - ** the cost by NlogN to cover the expense of sorting. */
1.1511 - if( pOrderBy ){
1.1512 - if( sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev) ){
1.1513 - flags |= WHERE_ORDERBY|WHERE_ROWID_RANGE;
1.1514 - if( rev ){
1.1515 - flags |= WHERE_REVERSE;
1.1516 - }
1.1517 - }else{
1.1518 - cost += cost*estLog(cost);
1.1519 - WHERETRACE(("... sorting increases cost to %.9g\n", cost));
1.1520 - }
1.1521 - }
1.1522 - if( cost<lowestCost ){
1.1523 - lowestCost = cost;
1.1524 - bestFlags = flags;
1.1525 - }
1.1526 -
1.1527 - /* If the pSrc table is the right table of a LEFT JOIN then we may not
1.1528 - ** use an index to satisfy IS NULL constraints on that table. This is
1.1529 - ** because columns might end up being NULL if the table does not match -
1.1530 - ** a circumstance which the index cannot help us discover. Ticket #2177.
1.1531 - */
1.1532 - if( (pSrc->jointype & JT_LEFT)!=0 ){
1.1533 - eqTermMask = WO_EQ|WO_IN;
1.1534 - }else{
1.1535 - eqTermMask = WO_EQ|WO_IN|WO_ISNULL;
1.1536 - }
1.1537 -
1.1538 - /* Look at each index.
1.1539 - */
1.1540 - for(; pProbe; pProbe=pProbe->pNext){
1.1541 - int i; /* Loop counter */
1.1542 - double inMultiplier = 1;
1.1543 -
1.1544 - WHERETRACE(("... index %s:\n", pProbe->zName));
1.1545 -
1.1546 - /* Count the number of columns in the index that are satisfied
1.1547 - ** by x=EXPR constraints or x IN (...) constraints.
1.1548 - */
1.1549 - flags = 0;
1.1550 - for(i=0; i<pProbe->nColumn; i++){
1.1551 - int j = pProbe->aiColumn[i];
1.1552 - pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pProbe);
1.1553 - if( pTerm==0 ) break;
1.1554 - flags |= WHERE_COLUMN_EQ;
1.1555 - if( pTerm->eOperator & WO_IN ){
1.1556 - Expr *pExpr = pTerm->pExpr;
1.1557 - flags |= WHERE_COLUMN_IN;
1.1558 - if( pExpr->pSelect!=0 ){
1.1559 - inMultiplier *= 25;
1.1560 - }else if( pExpr->pList!=0 ){
1.1561 - inMultiplier *= pExpr->pList->nExpr + 1;
1.1562 - }
1.1563 - }
1.1564 - }
1.1565 - cost = pProbe->aiRowEst[i] * inMultiplier * estLog(inMultiplier);
1.1566 - nEq = i;
1.1567 - if( pProbe->onError!=OE_None && (flags & WHERE_COLUMN_IN)==0
1.1568 - && nEq==pProbe->nColumn ){
1.1569 - flags |= WHERE_UNIQUE;
1.1570 - }
1.1571 - WHERETRACE(("...... nEq=%d inMult=%.9g cost=%.9g\n",nEq,inMultiplier,cost));
1.1572 -
1.1573 - /* Look for range constraints
1.1574 - */
1.1575 - if( nEq<pProbe->nColumn ){
1.1576 - int j = pProbe->aiColumn[nEq];
1.1577 - pTerm = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pProbe);
1.1578 - if( pTerm ){
1.1579 - flags |= WHERE_COLUMN_RANGE;
1.1580 - if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pProbe) ){
1.1581 - flags |= WHERE_TOP_LIMIT;
1.1582 - cost /= 3;
1.1583 - }
1.1584 - if( findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pProbe) ){
1.1585 - flags |= WHERE_BTM_LIMIT;
1.1586 - cost /= 3;
1.1587 - }
1.1588 - WHERETRACE(("...... range reduces cost to %.9g\n", cost));
1.1589 - }
1.1590 - }
1.1591 -
1.1592 - /* Add the additional cost of sorting if that is a factor.
1.1593 - */
1.1594 - if( pOrderBy ){
1.1595 - if( (flags & WHERE_COLUMN_IN)==0 &&
1.1596 - isSortingIndex(pParse,pWC->pMaskSet,pProbe,iCur,pOrderBy,nEq,&rev) ){
1.1597 - if( flags==0 ){
1.1598 - flags = WHERE_COLUMN_RANGE;
1.1599 - }
1.1600 - flags |= WHERE_ORDERBY;
1.1601 - if( rev ){
1.1602 - flags |= WHERE_REVERSE;
1.1603 - }
1.1604 - }else{
1.1605 - cost += cost*estLog(cost);
1.1606 - WHERETRACE(("...... orderby increases cost to %.9g\n", cost));
1.1607 - }
1.1608 - }
1.1609 -
1.1610 - /* Check to see if we can get away with using just the index without
1.1611 - ** ever reading the table. If that is the case, then halve the
1.1612 - ** cost of this index.
1.1613 - */
1.1614 - if( flags && pSrc->colUsed < (((Bitmask)1)<<(BMS-1)) ){
1.1615 - Bitmask m = pSrc->colUsed;
1.1616 - int j;
1.1617 - for(j=0; j<pProbe->nColumn; j++){
1.1618 - int x = pProbe->aiColumn[j];
1.1619 - if( x<BMS-1 ){
1.1620 - m &= ~(((Bitmask)1)<<x);
1.1621 - }
1.1622 - }
1.1623 - if( m==0 ){
1.1624 - flags |= WHERE_IDX_ONLY;
1.1625 - cost /= 2;
1.1626 - WHERETRACE(("...... idx-only reduces cost to %.9g\n", cost));
1.1627 - }
1.1628 - }
1.1629 -
1.1630 - /* If this index has achieved the lowest cost so far, then use it.
1.1631 - */
1.1632 - if( flags && cost < lowestCost ){
1.1633 - bestIdx = pProbe;
1.1634 - lowestCost = cost;
1.1635 - bestFlags = flags;
1.1636 - bestNEq = nEq;
1.1637 - }
1.1638 - }
1.1639 -
1.1640 - /* Report the best result
1.1641 - */
1.1642 - *ppIndex = bestIdx;
1.1643 - WHERETRACE(("best index is %s, cost=%.9g, flags=%x, nEq=%d\n",
1.1644 - bestIdx ? bestIdx->zName : "(none)", lowestCost, bestFlags, bestNEq));
1.1645 - *pFlags = bestFlags | eqTermMask;
1.1646 - *pnEq = bestNEq;
1.1647 - return lowestCost;
1.1648 -}
1.1649 -
1.1650 -
1.1651 -/*
1.1652 -** Disable a term in the WHERE clause. Except, do not disable the term
1.1653 -** if it controls a LEFT OUTER JOIN and it did not originate in the ON
1.1654 -** or USING clause of that join.
1.1655 -**
1.1656 -** Consider the term t2.z='ok' in the following queries:
1.1657 -**
1.1658 -** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
1.1659 -** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
1.1660 -** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
1.1661 -**
1.1662 -** The t2.z='ok' is disabled in the in (2) because it originates
1.1663 -** in the ON clause. The term is disabled in (3) because it is not part
1.1664 -** of a LEFT OUTER JOIN. In (1), the term is not disabled.
1.1665 -**
1.1666 -** Disabling a term causes that term to not be tested in the inner loop
1.1667 -** of the join. Disabling is an optimization. When terms are satisfied
1.1668 -** by indices, we disable them to prevent redundant tests in the inner
1.1669 -** loop. We would get the correct results if nothing were ever disabled,
1.1670 -** but joins might run a little slower. The trick is to disable as much
1.1671 -** as we can without disabling too much. If we disabled in (1), we'd get
1.1672 -** the wrong answer. See ticket #813.
1.1673 -*/
1.1674 -static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
1.1675 - if( pTerm
1.1676 - && (pTerm->flags & TERM_CODED)==0
1.1677 - && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
1.1678 - ){
1.1679 - pTerm->flags |= TERM_CODED;
1.1680 - if( pTerm->iParent>=0 ){
1.1681 - WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
1.1682 - if( (--pOther->nChild)==0 ){
1.1683 - disableTerm(pLevel, pOther);
1.1684 - }
1.1685 - }
1.1686 - }
1.1687 -}
1.1688 -
1.1689 -/*
1.1690 -** Generate code that builds a probe for an index.
1.1691 -**
1.1692 -** There should be nColumn values on the stack. The index
1.1693 -** to be probed is pIdx. Pop the values from the stack and
1.1694 -** replace them all with a single record that is the index
1.1695 -** problem.
1.1696 -*/
1.1697 -static void buildIndexProbe(
1.1698 - Vdbe *v, /* Generate code into this VM */
1.1699 - int nColumn, /* The number of columns to check for NULL */
1.1700 - Index *pIdx /* Index that we will be searching */
1.1701 -){
1.1702 - sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
1.1703 - sqlite3IndexAffinityStr(v, pIdx);
1.1704 -}
1.1705 -
1.1706 -
1.1707 -/*
1.1708 -** Generate code for a single equality term of the WHERE clause. An equality
1.1709 -** term can be either X=expr or X IN (...). pTerm is the term to be
1.1710 -** coded.
1.1711 -**
1.1712 -** The current value for the constraint is left on the top of the stack.
1.1713 -**
1.1714 -** For a constraint of the form X=expr, the expression is evaluated and its
1.1715 -** result is left on the stack. For constraints of the form X IN (...)
1.1716 -** this routine sets up a loop that will iterate over all values of X.
1.1717 -*/
1.1718 -static void codeEqualityTerm(
1.1719 - Parse *pParse, /* The parsing context */
1.1720 - WhereTerm *pTerm, /* The term of the WHERE clause to be coded */
1.1721 - WhereLevel *pLevel /* When level of the FROM clause we are working on */
1.1722 -){
1.1723 - Expr *pX = pTerm->pExpr;
1.1724 - Vdbe *v = pParse->pVdbe;
1.1725 - if( pX->op==TK_EQ ){
1.1726 - sqlite3ExprCode(pParse, pX->pRight);
1.1727 - }else if( pX->op==TK_ISNULL ){
1.1728 - sqlite3VdbeAddOp(v, OP_Null, 0, 0);
1.1729 -#ifndef SQLITE_OMIT_SUBQUERY
1.1730 - }else{
1.1731 - int iTab;
1.1732 - struct InLoop *pIn;
1.1733 -
1.1734 - assert( pX->op==TK_IN );
1.1735 - sqlite3CodeSubselect(pParse, pX);
1.1736 - iTab = pX->iTable;
1.1737 - sqlite3VdbeAddOp(v, OP_Rewind, iTab, 0);
1.1738 - VdbeComment((v, "# %.*s", pX->span.n, pX->span.z));
1.1739 - if( pLevel->nIn==0 ){
1.1740 - pLevel->nxt = sqlite3VdbeMakeLabel(v);
1.1741 - }
1.1742 - pLevel->nIn++;
1.1743 - pLevel->aInLoop = sqlite3DbReallocOrFree(pParse->db, pLevel->aInLoop,
1.1744 - sizeof(pLevel->aInLoop[0])*pLevel->nIn);
1.1745 - pIn = pLevel->aInLoop;
1.1746 - if( pIn ){
1.1747 - pIn += pLevel->nIn - 1;
1.1748 - pIn->iCur = iTab;
1.1749 - pIn->topAddr = sqlite3VdbeAddOp(v, OP_Column, iTab, 0);
1.1750 - sqlite3VdbeAddOp(v, OP_IsNull, -1, 0);
1.1751 - }else{
1.1752 - pLevel->nIn = 0;
1.1753 - }
1.1754 -#endif
1.1755 - }
1.1756 - disableTerm(pLevel, pTerm);
1.1757 -}
1.1758 -
1.1759 -/*
1.1760 -** Generate code that will evaluate all == and IN constraints for an
1.1761 -** index. The values for all constraints are left on the stack.
1.1762 -**
1.1763 -** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
1.1764 -** Suppose the WHERE clause is this: a==5 AND b IN (1,2,3) AND c>5 AND c<10
1.1765 -** The index has as many as three equality constraints, but in this
1.1766 -** example, the third "c" value is an inequality. So only two
1.1767 -** constraints are coded. This routine will generate code to evaluate
1.1768 -** a==5 and b IN (1,2,3). The current values for a and b will be left
1.1769 -** on the stack - a is the deepest and b the shallowest.
1.1770 -**
1.1771 -** In the example above nEq==2. But this subroutine works for any value
1.1772 -** of nEq including 0. If nEq==0, this routine is nearly a no-op.
1.1773 -** The only thing it does is allocate the pLevel->iMem memory cell.
1.1774 -**
1.1775 -** This routine always allocates at least one memory cell and puts
1.1776 -** the address of that memory cell in pLevel->iMem. The code that
1.1777 -** calls this routine will use pLevel->iMem to store the termination
1.1778 -** key value of the loop. If one or more IN operators appear, then
1.1779 -** this routine allocates an additional nEq memory cells for internal
1.1780 -** use.
1.1781 -*/
1.1782 -static void codeAllEqualityTerms(
1.1783 - Parse *pParse, /* Parsing context */
1.1784 - WhereLevel *pLevel, /* Which nested loop of the FROM we are coding */
1.1785 - WhereClause *pWC, /* The WHERE clause */
1.1786 - Bitmask notReady /* Which parts of FROM have not yet been coded */
1.1787 -){
1.1788 - int nEq = pLevel->nEq; /* The number of == or IN constraints to code */
1.1789 - int termsInMem = 0; /* If true, store value in mem[] cells */
1.1790 - Vdbe *v = pParse->pVdbe; /* The virtual machine under construction */
1.1791 - Index *pIdx = pLevel->pIdx; /* The index being used for this loop */
1.1792 - int iCur = pLevel->iTabCur; /* The cursor of the table */
1.1793 - WhereTerm *pTerm; /* A single constraint term */
1.1794 - int j; /* Loop counter */
1.1795 -
1.1796 - /* Figure out how many memory cells we will need then allocate them.
1.1797 - ** We always need at least one used to store the loop terminator
1.1798 - ** value. If there are IN operators we'll need one for each == or
1.1799 - ** IN constraint.
1.1800 - */
1.1801 - pLevel->iMem = pParse->nMem++;
1.1802 - if( pLevel->flags & WHERE_COLUMN_IN ){
1.1803 - pParse->nMem += pLevel->nEq;
1.1804 - termsInMem = 1;
1.1805 - }
1.1806 -
1.1807 - /* Evaluate the equality constraints
1.1808 - */
1.1809 - assert( pIdx->nColumn>=nEq );
1.1810 - for(j=0; j<nEq; j++){
1.1811 - int k = pIdx->aiColumn[j];
1.1812 - pTerm = findTerm(pWC, iCur, k, notReady, pLevel->flags, pIdx);
1.1813 - if( pTerm==0 ) break;
1.1814 - assert( (pTerm->flags & TERM_CODED)==0 );
1.1815 - codeEqualityTerm(pParse, pTerm, pLevel);
1.1816 - if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
1.1817 - sqlite3VdbeAddOp(v, OP_IsNull, termsInMem ? -1 : -(j+1), pLevel->brk);
1.1818 - }
1.1819 - if( termsInMem ){
1.1820 - sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem+j+1, 1);
1.1821 - }
1.1822 - }
1.1823 -
1.1824 - /* Make sure all the constraint values are on the top of the stack
1.1825 - */
1.1826 - if( termsInMem ){
1.1827 - for(j=0; j<nEq; j++){
1.1828 - sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem+j+1, 0);
1.1829 - }
1.1830 - }
1.1831 -}
1.1832 -
1.1833 -#if defined(SQLITE_TEST)
1.1834 -/*
1.1835 -** The following variable holds a text description of query plan generated
1.1836 -** by the most recent call to sqlite3WhereBegin(). Each call to WhereBegin
1.1837 -** overwrites the previous. This information is used for testing and
1.1838 -** analysis only.
1.1839 -*/
1.1840 -char sqlite3_query_plan[BMS*2*40]; /* Text of the join */
1.1841 -static int nQPlan = 0; /* Next free slow in _query_plan[] */
1.1842 -
1.1843 -#endif /* SQLITE_TEST */
1.1844 -
1.1845 -
1.1846 -/*
1.1847 -** Free a WhereInfo structure
1.1848 -*/
1.1849 -static void whereInfoFree(WhereInfo *pWInfo){
1.1850 - if( pWInfo ){
1.1851 - int i;
1.1852 - for(i=0; i<pWInfo->nLevel; i++){
1.1853 - sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
1.1854 - if( pInfo ){
1.1855 - if( pInfo->needToFreeIdxStr ){
1.1856 - /* Coverage: Don't think this can be reached. By the time this
1.1857 - ** function is called, the index-strings have been passed
1.1858 - ** to the vdbe layer for deletion.
1.1859 - */
1.1860 - sqlite3_free(pInfo->idxStr);
1.1861 - }
1.1862 - sqlite3_free(pInfo);
1.1863 - }
1.1864 - }
1.1865 - sqlite3_free(pWInfo);
1.1866 - }
1.1867 -}
1.1868 -
1.1869 -
1.1870 -/*
1.1871 -** Generate the beginning of the loop used for WHERE clause processing.
1.1872 -** The return value is a pointer to an opaque structure that contains
1.1873 -** information needed to terminate the loop. Later, the calling routine
1.1874 -** should invoke sqlite3WhereEnd() with the return value of this function
1.1875 -** in order to complete the WHERE clause processing.
1.1876 -**
1.1877 -** If an error occurs, this routine returns NULL.
1.1878 -**
1.1879 -** The basic idea is to do a nested loop, one loop for each table in
1.1880 -** the FROM clause of a select. (INSERT and UPDATE statements are the
1.1881 -** same as a SELECT with only a single table in the FROM clause.) For
1.1882 -** example, if the SQL is this:
1.1883 -**
1.1884 -** SELECT * FROM t1, t2, t3 WHERE ...;
1.1885 -**
1.1886 -** Then the code generated is conceptually like the following:
1.1887 -**
1.1888 -** foreach row1 in t1 do \ Code generated
1.1889 -** foreach row2 in t2 do |-- by sqlite3WhereBegin()
1.1890 -** foreach row3 in t3 do /
1.1891 -** ...
1.1892 -** end \ Code generated
1.1893 -** end |-- by sqlite3WhereEnd()
1.1894 -** end /
1.1895 -**
1.1896 -** Note that the loops might not be nested in the order in which they
1.1897 -** appear in the FROM clause if a different order is better able to make
1.1898 -** use of indices. Note also that when the IN operator appears in
1.1899 -** the WHERE clause, it might result in additional nested loops for
1.1900 -** scanning through all values on the right-hand side of the IN.
1.1901 -**
1.1902 -** There are Btree cursors associated with each table. t1 uses cursor
1.1903 -** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor.
1.1904 -** And so forth. This routine generates code to open those VDBE cursors
1.1905 -** and sqlite3WhereEnd() generates the code to close them.
1.1906 -**
1.1907 -** The code that sqlite3WhereBegin() generates leaves the cursors named
1.1908 -** in pTabList pointing at their appropriate entries. The [...] code
1.1909 -** can use OP_Column and OP_Rowid opcodes on these cursors to extract
1.1910 -** data from the various tables of the loop.
1.1911 -**
1.1912 -** If the WHERE clause is empty, the foreach loops must each scan their
1.1913 -** entire tables. Thus a three-way join is an O(N^3) operation. But if
1.1914 -** the tables have indices and there are terms in the WHERE clause that
1.1915 -** refer to those indices, a complete table scan can be avoided and the
1.1916 -** code will run much faster. Most of the work of this routine is checking
1.1917 -** to see if there are indices that can be used to speed up the loop.
1.1918 -**
1.1919 -** Terms of the WHERE clause are also used to limit which rows actually
1.1920 -** make it to the "..." in the middle of the loop. After each "foreach",
1.1921 -** terms of the WHERE clause that use only terms in that loop and outer
1.1922 -** loops are evaluated and if false a jump is made around all subsequent
1.1923 -** inner loops (or around the "..." if the test occurs within the inner-
1.1924 -** most loop)
1.1925 -**
1.1926 -** OUTER JOINS
1.1927 -**
1.1928 -** An outer join of tables t1 and t2 is conceptally coded as follows:
1.1929 -**
1.1930 -** foreach row1 in t1 do
1.1931 -** flag = 0
1.1932 -** foreach row2 in t2 do
1.1933 -** start:
1.1934 -** ...
1.1935 -** flag = 1
1.1936 -** end
1.1937 -** if flag==0 then
1.1938 -** move the row2 cursor to a null row
1.1939 -** goto start
1.1940 -** fi
1.1941 -** end
1.1942 -**
1.1943 -** ORDER BY CLAUSE PROCESSING
1.1944 -**
1.1945 -** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
1.1946 -** if there is one. If there is no ORDER BY clause or if this routine
1.1947 -** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
1.1948 -**
1.1949 -** If an index can be used so that the natural output order of the table
1.1950 -** scan is correct for the ORDER BY clause, then that index is used and
1.1951 -** *ppOrderBy is set to NULL. This is an optimization that prevents an
1.1952 -** unnecessary sort of the result set if an index appropriate for the
1.1953 -** ORDER BY clause already exists.
1.1954 -**
1.1955 -** If the where clause loops cannot be arranged to provide the correct
1.1956 -** output order, then the *ppOrderBy is unchanged.
1.1957 -*/
1.1958 -WhereInfo *sqlite3WhereBegin(
1.1959 - Parse *pParse, /* The parser context */
1.1960 - SrcList *pTabList, /* A list of all tables to be scanned */
1.1961 - Expr *pWhere, /* The WHERE clause */
1.1962 - ExprList **ppOrderBy /* An ORDER BY clause, or NULL */
1.1963 -){
1.1964 - int i; /* Loop counter */
1.1965 - WhereInfo *pWInfo; /* Will become the return value of this function */
1.1966 - Vdbe *v = pParse->pVdbe; /* The virtual database engine */
1.1967 - int brk, cont = 0; /* Addresses used during code generation */
1.1968 - Bitmask notReady; /* Cursors that are not yet positioned */
1.1969 - WhereTerm *pTerm; /* A single term in the WHERE clause */
1.1970 - ExprMaskSet maskSet; /* The expression mask set */
1.1971 - WhereClause wc; /* The WHERE clause is divided into these terms */
1.1972 - struct SrcList_item *pTabItem; /* A single entry from pTabList */
1.1973 - WhereLevel *pLevel; /* A single level in the pWInfo list */
1.1974 - int iFrom; /* First unused FROM clause element */
1.1975 - int andFlags; /* AND-ed combination of all wc.a[].flags */
1.1976 - sqlite3 *db; /* Database connection */
1.1977 -
1.1978 - /* The number of tables in the FROM clause is limited by the number of
1.1979 - ** bits in a Bitmask
1.1980 - */
1.1981 - if( pTabList->nSrc>BMS ){
1.1982 - sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
1.1983 - return 0;
1.1984 - }
1.1985 -
1.1986 - /* Split the WHERE clause into separate subexpressions where each
1.1987 - ** subexpression is separated by an AND operator.
1.1988 - */
1.1989 - initMaskSet(&maskSet);
1.1990 - whereClauseInit(&wc, pParse, &maskSet);
1.1991 - whereSplit(&wc, pWhere, TK_AND);
1.1992 -
1.1993 - /* Allocate and initialize the WhereInfo structure that will become the
1.1994 - ** return value.
1.1995 - */
1.1996 - db = pParse->db;
1.1997 - pWInfo = sqlite3DbMallocZero(db,
1.1998 - sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel));
1.1999 - if( db->mallocFailed ){
1.2000 - goto whereBeginNoMem;
1.2001 - }
1.2002 - pWInfo->nLevel = pTabList->nSrc;
1.2003 - pWInfo->pParse = pParse;
1.2004 - pWInfo->pTabList = pTabList;
1.2005 - pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
1.2006 -
1.2007 - /* Special case: a WHERE clause that is constant. Evaluate the
1.2008 - ** expression and either jump over all of the code or fall thru.
1.2009 - */
1.2010 - if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
1.2011 - sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1);
1.2012 - pWhere = 0;
1.2013 - }
1.2014 -
1.2015 - /* Analyze all of the subexpressions. Note that exprAnalyze() might
1.2016 - ** add new virtual terms onto the end of the WHERE clause. We do not
1.2017 - ** want to analyze these virtual terms, so start analyzing at the end
1.2018 - ** and work forward so that the added virtual terms are never processed.
1.2019 - */
1.2020 - for(i=0; i<pTabList->nSrc; i++){
1.2021 - createMask(&maskSet, pTabList->a[i].iCursor);
1.2022 - }
1.2023 - exprAnalyzeAll(pTabList, &wc);
1.2024 - if( db->mallocFailed ){
1.2025 - goto whereBeginNoMem;
1.2026 - }
1.2027 -
1.2028 - /* Chose the best index to use for each table in the FROM clause.
1.2029 - **
1.2030 - ** This loop fills in the following fields:
1.2031 - **
1.2032 - ** pWInfo->a[].pIdx The index to use for this level of the loop.
1.2033 - ** pWInfo->a[].flags WHERE_xxx flags associated with pIdx
1.2034 - ** pWInfo->a[].nEq The number of == and IN constraints
1.2035 - ** pWInfo->a[].iFrom When term of the FROM clause is being coded
1.2036 - ** pWInfo->a[].iTabCur The VDBE cursor for the database table
1.2037 - ** pWInfo->a[].iIdxCur The VDBE cursor for the index
1.2038 - **
1.2039 - ** This loop also figures out the nesting order of tables in the FROM
1.2040 - ** clause.
1.2041 - */
1.2042 - notReady = ~(Bitmask)0;
1.2043 - pTabItem = pTabList->a;
1.2044 - pLevel = pWInfo->a;
1.2045 - andFlags = ~0;
1.2046 - WHERETRACE(("*** Optimizer Start ***\n"));
1.2047 - for(i=iFrom=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
1.2048 - Index *pIdx; /* Index for FROM table at pTabItem */
1.2049 - int flags; /* Flags asssociated with pIdx */
1.2050 - int nEq; /* Number of == or IN constraints */
1.2051 - double cost; /* The cost for pIdx */
1.2052 - int j; /* For looping over FROM tables */
1.2053 - Index *pBest = 0; /* The best index seen so far */
1.2054 - int bestFlags = 0; /* Flags associated with pBest */
1.2055 - int bestNEq = 0; /* nEq associated with pBest */
1.2056 - double lowestCost; /* Cost of the pBest */
1.2057 - int bestJ = 0; /* The value of j */
1.2058 - Bitmask m; /* Bitmask value for j or bestJ */
1.2059 - int once = 0; /* True when first table is seen */
1.2060 - sqlite3_index_info *pIndex; /* Current virtual index */
1.2061 -
1.2062 - lowestCost = SQLITE_BIG_DBL;
1.2063 - for(j=iFrom, pTabItem=&pTabList->a[j]; j<pTabList->nSrc; j++, pTabItem++){
1.2064 - int doNotReorder; /* True if this table should not be reordered */
1.2065 -
1.2066 - doNotReorder = (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;
1.2067 - if( once && doNotReorder ) break;
1.2068 - m = getMask(&maskSet, pTabItem->iCursor);
1.2069 - if( (m & notReady)==0 ){
1.2070 - if( j==iFrom ) iFrom++;
1.2071 - continue;
1.2072 - }
1.2073 - assert( pTabItem->pTab );
1.2074 -#ifndef SQLITE_OMIT_VIRTUALTABLE
1.2075 - if( IsVirtual(pTabItem->pTab) ){
1.2076 - sqlite3_index_info **ppIdxInfo = &pWInfo->a[j].pIdxInfo;
1.2077 - cost = bestVirtualIndex(pParse, &wc, pTabItem, notReady,
1.2078 - ppOrderBy ? *ppOrderBy : 0, i==0,
1.2079 - ppIdxInfo);
1.2080 - flags = WHERE_VIRTUALTABLE;
1.2081 - pIndex = *ppIdxInfo;
1.2082 - if( pIndex && pIndex->orderByConsumed ){
1.2083 - flags = WHERE_VIRTUALTABLE | WHERE_ORDERBY;
1.2084 - }
1.2085 - pIdx = 0;
1.2086 - nEq = 0;
1.2087 - if( (SQLITE_BIG_DBL/2.0)<cost ){
1.2088 - /* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
1.2089 - ** inital value of lowestCost in this loop. If it is, then
1.2090 - ** the (cost<lowestCost) test below will never be true and
1.2091 - ** pLevel->pBestIdx never set.
1.2092 - */
1.2093 - cost = (SQLITE_BIG_DBL/2.0);
1.2094 - }
1.2095 - }else
1.2096 -#endif
1.2097 - {
1.2098 - cost = bestIndex(pParse, &wc, pTabItem, notReady,
1.2099 - (i==0 && ppOrderBy) ? *ppOrderBy : 0,
1.2100 - &pIdx, &flags, &nEq);
1.2101 - pIndex = 0;
1.2102 - }
1.2103 - if( cost<lowestCost ){
1.2104 - once = 1;
1.2105 - lowestCost = cost;
1.2106 - pBest = pIdx;
1.2107 - bestFlags = flags;
1.2108 - bestNEq = nEq;
1.2109 - bestJ = j;
1.2110 - pLevel->pBestIdx = pIndex;
1.2111 - }
1.2112 - if( doNotReorder ) break;
1.2113 - }
1.2114 - WHERETRACE(("*** Optimizer choose table %d for loop %d\n", bestJ,
1.2115 - pLevel-pWInfo->a));
1.2116 - if( (bestFlags & WHERE_ORDERBY)!=0 ){
1.2117 - *ppOrderBy = 0;
1.2118 - }
1.2119 - andFlags &= bestFlags;
1.2120 - pLevel->flags = bestFlags;
1.2121 - pLevel->pIdx = pBest;
1.2122 - pLevel->nEq = bestNEq;
1.2123 - pLevel->aInLoop = 0;
1.2124 - pLevel->nIn = 0;
1.2125 - if( pBest ){
1.2126 - pLevel->iIdxCur = pParse->nTab++;
1.2127 - }else{
1.2128 - pLevel->iIdxCur = -1;
1.2129 - }
1.2130 - notReady &= ~getMask(&maskSet, pTabList->a[bestJ].iCursor);
1.2131 - pLevel->iFrom = bestJ;
1.2132 - }
1.2133 - WHERETRACE(("*** Optimizer Finished ***\n"));
1.2134 -
1.2135 - /* If the total query only selects a single row, then the ORDER BY
1.2136 - ** clause is irrelevant.
1.2137 - */
1.2138 - if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){
1.2139 - *ppOrderBy = 0;
1.2140 - }
1.2141 -
1.2142 - /* Open all tables in the pTabList and any indices selected for
1.2143 - ** searching those tables.
1.2144 - */
1.2145 - sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
1.2146 - for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
1.2147 - Table *pTab; /* Table to open */
1.2148 - Index *pIx; /* Index used to access pTab (if any) */
1.2149 - int iDb; /* Index of database containing table/index */
1.2150 - int iIdxCur = pLevel->iIdxCur;
1.2151 -
1.2152 -#ifndef SQLITE_OMIT_EXPLAIN
1.2153 - if( pParse->explain==2 ){
1.2154 - char *zMsg;
1.2155 - struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
1.2156 - zMsg = sqlite3MPrintf(db, "TABLE %s", pItem->zName);
1.2157 - if( pItem->zAlias ){
1.2158 - zMsg = sqlite3MPrintf(db, "%z AS %s", zMsg, pItem->zAlias);
1.2159 - }
1.2160 - if( (pIx = pLevel->pIdx)!=0 ){
1.2161 - zMsg = sqlite3MPrintf(db, "%z WITH INDEX %s", zMsg, pIx->zName);
1.2162 - }else if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
1.2163 - zMsg = sqlite3MPrintf(db, "%z USING PRIMARY KEY", zMsg);
1.2164 - }
1.2165 -#ifndef SQLITE_OMIT_VIRTUALTABLE
1.2166 - else if( pLevel->pBestIdx ){
1.2167 - sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
1.2168 - zMsg = sqlite3MPrintf(db, "%z VIRTUAL TABLE INDEX %d:%s", zMsg,
1.2169 - pBestIdx->idxNum, pBestIdx->idxStr);
1.2170 - }
1.2171 -#endif
1.2172 - if( pLevel->flags & WHERE_ORDERBY ){
1.2173 - zMsg = sqlite3MPrintf(db, "%z ORDER BY", zMsg);
1.2174 - }
1.2175 - sqlite3VdbeOp3(v, OP_Explain, i, pLevel->iFrom, zMsg, P3_DYNAMIC);
1.2176 - }
1.2177 -#endif /* SQLITE_OMIT_EXPLAIN */
1.2178 - pTabItem = &pTabList->a[pLevel->iFrom];
1.2179 - pTab = pTabItem->pTab;
1.2180 - iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
1.2181 - if( pTab->isEphem || pTab->pSelect ) continue;
1.2182 -#ifndef SQLITE_OMIT_VIRTUALTABLE
1.2183 - if( pLevel->pBestIdx ){
1.2184 - int iCur = pTabItem->iCursor;
1.2185 - sqlite3VdbeOp3(v, OP_VOpen, iCur, 0, (const char*)pTab->pVtab, P3_VTAB);
1.2186 - }else
1.2187 -#endif
1.2188 - if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
1.2189 - sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, OP_OpenRead);
1.2190 - if( pTab->nCol<(sizeof(Bitmask)*8) ){
1.2191 - Bitmask b = pTabItem->colUsed;
1.2192 - int n = 0;
1.2193 - for(; b; b=b>>1, n++){}
1.2194 - sqlite3VdbeChangeP2(v, sqlite3VdbeCurrentAddr(v)-1, n);
1.2195 - assert( n<=pTab->nCol );
1.2196 - }
1.2197 - }else{
1.2198 - sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
1.2199 - }
1.2200 - pLevel->iTabCur = pTabItem->iCursor;
1.2201 - if( (pIx = pLevel->pIdx)!=0 ){
1.2202 - KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
1.2203 - assert( pIx->pSchema==pTab->pSchema );
1.2204 - sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
1.2205 - VdbeComment((v, "# %s", pIx->zName));
1.2206 - sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
1.2207 - (char*)pKey, P3_KEYINFO_HANDOFF);
1.2208 - }
1.2209 - if( (pLevel->flags & (WHERE_IDX_ONLY|WHERE_COLUMN_RANGE))!=0 ){
1.2210 - /* Only call OP_SetNumColumns on the index if we might later use
1.2211 - ** OP_Column on the index. */
1.2212 - sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
1.2213 - }
1.2214 - sqlite3CodeVerifySchema(pParse, iDb);
1.2215 - }
1.2216 - pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
1.2217 -
1.2218 - /* Generate the code to do the search. Each iteration of the for
1.2219 - ** loop below generates code for a single nested loop of the VM
1.2220 - ** program.
1.2221 - */
1.2222 - notReady = ~(Bitmask)0;
1.2223 - for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
1.2224 - int j;
1.2225 - int iCur = pTabItem->iCursor; /* The VDBE cursor for the table */
1.2226 - Index *pIdx; /* The index we will be using */
1.2227 - int nxt; /* Where to jump to continue with the next IN case */
1.2228 - int iIdxCur; /* The VDBE cursor for the index */
1.2229 - int omitTable; /* True if we use the index only */
1.2230 - int bRev; /* True if we need to scan in reverse order */
1.2231 -
1.2232 - pTabItem = &pTabList->a[pLevel->iFrom];
1.2233 - iCur = pTabItem->iCursor;
1.2234 - pIdx = pLevel->pIdx;
1.2235 - iIdxCur = pLevel->iIdxCur;
1.2236 - bRev = (pLevel->flags & WHERE_REVERSE)!=0;
1.2237 - omitTable = (pLevel->flags & WHERE_IDX_ONLY)!=0;
1.2238 -
1.2239 - /* Create labels for the "break" and "continue" instructions
1.2240 - ** for the current loop. Jump to brk to break out of a loop.
1.2241 - ** Jump to cont to go immediately to the next iteration of the
1.2242 - ** loop.
1.2243 - **
1.2244 - ** When there is an IN operator, we also have a "nxt" label that
1.2245 - ** means to continue with the next IN value combination. When
1.2246 - ** there are no IN operators in the constraints, the "nxt" label
1.2247 - ** is the same as "brk".
1.2248 - */
1.2249 - brk = pLevel->brk = pLevel->nxt = sqlite3VdbeMakeLabel(v);
1.2250 - cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
1.2251 -
1.2252 - /* If this is the right table of a LEFT OUTER JOIN, allocate and
1.2253 - ** initialize a memory cell that records if this table matches any
1.2254 - ** row of the left table of the join.
1.2255 - */
1.2256 - if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
1.2257 - if( !pParse->nMem ) pParse->nMem++;
1.2258 - pLevel->iLeftJoin = pParse->nMem++;
1.2259 - sqlite3VdbeAddOp(v, OP_MemInt, 0, pLevel->iLeftJoin);
1.2260 - VdbeComment((v, "# init LEFT JOIN no-match flag"));
1.2261 - }
1.2262 -
1.2263 -#ifndef SQLITE_OMIT_VIRTUALTABLE
1.2264 - if( pLevel->pBestIdx ){
1.2265 - /* Case 0: The table is a virtual-table. Use the VFilter and VNext
1.2266 - ** to access the data.
1.2267 - */
1.2268 - int j;
1.2269 - sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
1.2270 - int nConstraint = pBestIdx->nConstraint;
1.2271 - struct sqlite3_index_constraint_usage *aUsage =
1.2272 - pBestIdx->aConstraintUsage;
1.2273 - const struct sqlite3_index_constraint *aConstraint =
1.2274 - pBestIdx->aConstraint;
1.2275 -
1.2276 - for(j=1; j<=nConstraint; j++){
1.2277 - int k;
1.2278 - for(k=0; k<nConstraint; k++){
1.2279 - if( aUsage[k].argvIndex==j ){
1.2280 - int iTerm = aConstraint[k].iTermOffset;
1.2281 - sqlite3ExprCode(pParse, wc.a[iTerm].pExpr->pRight);
1.2282 - break;
1.2283 - }
1.2284 - }
1.2285 - if( k==nConstraint ) break;
1.2286 - }
1.2287 - sqlite3VdbeAddOp(v, OP_Integer, j-1, 0);
1.2288 - sqlite3VdbeAddOp(v, OP_Integer, pBestIdx->idxNum, 0);
1.2289 - sqlite3VdbeOp3(v, OP_VFilter, iCur, brk, pBestIdx->idxStr,
1.2290 - pBestIdx->needToFreeIdxStr ? P3_MPRINTF : P3_STATIC);
1.2291 - pBestIdx->needToFreeIdxStr = 0;
1.2292 - for(j=0; j<pBestIdx->nConstraint; j++){
1.2293 - if( aUsage[j].omit ){
1.2294 - int iTerm = aConstraint[j].iTermOffset;
1.2295 - disableTerm(pLevel, &wc.a[iTerm]);
1.2296 - }
1.2297 - }
1.2298 - pLevel->op = OP_VNext;
1.2299 - pLevel->p1 = iCur;
1.2300 - pLevel->p2 = sqlite3VdbeCurrentAddr(v);
1.2301 - }else
1.2302 -#endif /* SQLITE_OMIT_VIRTUALTABLE */
1.2303 -
1.2304 - if( pLevel->flags & WHERE_ROWID_EQ ){
1.2305 - /* Case 1: We can directly reference a single row using an
1.2306 - ** equality comparison against the ROWID field. Or
1.2307 - ** we reference multiple rows using a "rowid IN (...)"
1.2308 - ** construct.
1.2309 - */
1.2310 - pTerm = findTerm(&wc, iCur, -1, notReady, WO_EQ|WO_IN, 0);
1.2311 - assert( pTerm!=0 );
1.2312 - assert( pTerm->pExpr!=0 );
1.2313 - assert( pTerm->leftCursor==iCur );
1.2314 - assert( omitTable==0 );
1.2315 - codeEqualityTerm(pParse, pTerm, pLevel);
1.2316 - nxt = pLevel->nxt;
1.2317 - sqlite3VdbeAddOp(v, OP_MustBeInt, 1, nxt);
1.2318 - sqlite3VdbeAddOp(v, OP_NotExists, iCur, nxt);
1.2319 - VdbeComment((v, "pk"));
1.2320 - pLevel->op = OP_Noop;
1.2321 - }else if( pLevel->flags & WHERE_ROWID_RANGE ){
1.2322 - /* Case 2: We have an inequality comparison against the ROWID field.
1.2323 - */
1.2324 - int testOp = OP_Noop;
1.2325 - int start;
1.2326 - WhereTerm *pStart, *pEnd;
1.2327 -
1.2328 - assert( omitTable==0 );
1.2329 - pStart = findTerm(&wc, iCur, -1, notReady, WO_GT|WO_GE, 0);
1.2330 - pEnd = findTerm(&wc, iCur, -1, notReady, WO_LT|WO_LE, 0);
1.2331 - if( bRev ){
1.2332 - pTerm = pStart;
1.2333 - pStart = pEnd;
1.2334 - pEnd = pTerm;
1.2335 - }
1.2336 - if( pStart ){
1.2337 - Expr *pX;
1.2338 - pX = pStart->pExpr;
1.2339 - assert( pX!=0 );
1.2340 - assert( pStart->leftCursor==iCur );
1.2341 - sqlite3ExprCode(pParse, pX->pRight);
1.2342 - sqlite3VdbeAddOp(v, OP_ForceInt, pX->op==TK_LE || pX->op==TK_GT, brk);
1.2343 - sqlite3VdbeAddOp(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk);
1.2344 - VdbeComment((v, "pk"));
1.2345 - disableTerm(pLevel, pStart);
1.2346 - }else{
1.2347 - sqlite3VdbeAddOp(v, bRev ? OP_Last : OP_Rewind, iCur, brk);
1.2348 - }
1.2349 - if( pEnd ){
1.2350 - Expr *pX;
1.2351 - pX = pEnd->pExpr;
1.2352 - assert( pX!=0 );
1.2353 - assert( pEnd->leftCursor==iCur );
1.2354 - sqlite3ExprCode(pParse, pX->pRight);
1.2355 - pLevel->iMem = pParse->nMem++;
1.2356 - sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
1.2357 - if( pX->op==TK_LT || pX->op==TK_GT ){
1.2358 - testOp = bRev ? OP_Le : OP_Ge;
1.2359 - }else{
1.2360 - testOp = bRev ? OP_Lt : OP_Gt;
1.2361 - }
1.2362 - disableTerm(pLevel, pEnd);
1.2363 - }
1.2364 - start = sqlite3VdbeCurrentAddr(v);
1.2365 - pLevel->op = bRev ? OP_Prev : OP_Next;
1.2366 - pLevel->p1 = iCur;
1.2367 - pLevel->p2 = start;
1.2368 - if( testOp!=OP_Noop ){
1.2369 - sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
1.2370 - sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
1.2371 - sqlite3VdbeAddOp(v, testOp, SQLITE_AFF_NUMERIC|0x100, brk);
1.2372 - }
1.2373 - }else if( pLevel->flags & WHERE_COLUMN_RANGE ){
1.2374 - /* Case 3: The WHERE clause term that refers to the right-most
1.2375 - ** column of the index is an inequality. For example, if
1.2376 - ** the index is on (x,y,z) and the WHERE clause is of the
1.2377 - ** form "x=5 AND y<10" then this case is used. Only the
1.2378 - ** right-most column can be an inequality - the rest must
1.2379 - ** use the "==" and "IN" operators.
1.2380 - **
1.2381 - ** This case is also used when there are no WHERE clause
1.2382 - ** constraints but an index is selected anyway, in order
1.2383 - ** to force the output order to conform to an ORDER BY.
1.2384 - */
1.2385 - int start;
1.2386 - int nEq = pLevel->nEq;
1.2387 - int topEq=0; /* True if top limit uses ==. False is strictly < */
1.2388 - int btmEq=0; /* True if btm limit uses ==. False if strictly > */
1.2389 - int topOp, btmOp; /* Operators for the top and bottom search bounds */
1.2390 - int testOp;
1.2391 - int topLimit = (pLevel->flags & WHERE_TOP_LIMIT)!=0;
1.2392 - int btmLimit = (pLevel->flags & WHERE_BTM_LIMIT)!=0;
1.2393 -
1.2394 - /* Generate code to evaluate all constraint terms using == or IN
1.2395 - ** and level the values of those terms on the stack.
1.2396 - */
1.2397 - codeAllEqualityTerms(pParse, pLevel, &wc, notReady);
1.2398 -
1.2399 - /* Duplicate the equality term values because they will all be
1.2400 - ** used twice: once to make the termination key and once to make the
1.2401 - ** start key.
1.2402 - */
1.2403 - for(j=0; j<nEq; j++){
1.2404 - sqlite3VdbeAddOp(v, OP_Dup, nEq-1, 0);
1.2405 - }
1.2406 -
1.2407 - /* Figure out what comparison operators to use for top and bottom
1.2408 - ** search bounds. For an ascending index, the bottom bound is a > or >=
1.2409 - ** operator and the top bound is a < or <= operator. For a descending
1.2410 - ** index the operators are reversed.
1.2411 - */
1.2412 - if( pIdx->aSortOrder[nEq]==SQLITE_SO_ASC ){
1.2413 - topOp = WO_LT|WO_LE;
1.2414 - btmOp = WO_GT|WO_GE;
1.2415 - }else{
1.2416 - topOp = WO_GT|WO_GE;
1.2417 - btmOp = WO_LT|WO_LE;
1.2418 - SWAP(int, topLimit, btmLimit);
1.2419 - }
1.2420 -
1.2421 - /* Generate the termination key. This is the key value that
1.2422 - ** will end the search. There is no termination key if there
1.2423 - ** are no equality terms and no "X<..." term.
1.2424 - **
1.2425 - ** 2002-Dec-04: On a reverse-order scan, the so-called "termination"
1.2426 - ** key computed here really ends up being the start key.
1.2427 - */
1.2428 - nxt = pLevel->nxt;
1.2429 - if( topLimit ){
1.2430 - Expr *pX;
1.2431 - int k = pIdx->aiColumn[j];
1.2432 - pTerm = findTerm(&wc, iCur, k, notReady, topOp, pIdx);
1.2433 - assert( pTerm!=0 );
1.2434 - pX = pTerm->pExpr;
1.2435 - assert( (pTerm->flags & TERM_CODED)==0 );
1.2436 - sqlite3ExprCode(pParse, pX->pRight);
1.2437 - sqlite3VdbeAddOp(v, OP_IsNull, -(nEq*2+1), nxt);
1.2438 - topEq = pTerm->eOperator & (WO_LE|WO_GE);
1.2439 - disableTerm(pLevel, pTerm);
1.2440 - testOp = OP_IdxGE;
1.2441 - }else{
1.2442 - testOp = nEq>0 ? OP_IdxGE : OP_Noop;
1.2443 - topEq = 1;
1.2444 - }
1.2445 - if( testOp!=OP_Noop ){
1.2446 - int nCol = nEq + topLimit;
1.2447 - pLevel->iMem = pParse->nMem++;
1.2448 - buildIndexProbe(v, nCol, pIdx);
1.2449 - if( bRev ){
1.2450 - int op = topEq ? OP_MoveLe : OP_MoveLt;
1.2451 - sqlite3VdbeAddOp(v, op, iIdxCur, nxt);
1.2452 - }else{
1.2453 - sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
1.2454 - }
1.2455 - }else if( bRev ){
1.2456 - sqlite3VdbeAddOp(v, OP_Last, iIdxCur, brk);
1.2457 - }
1.2458 -
1.2459 - /* Generate the start key. This is the key that defines the lower
1.2460 - ** bound on the search. There is no start key if there are no
1.2461 - ** equality terms and if there is no "X>..." term. In
1.2462 - ** that case, generate a "Rewind" instruction in place of the
1.2463 - ** start key search.
1.2464 - **
1.2465 - ** 2002-Dec-04: In the case of a reverse-order search, the so-called
1.2466 - ** "start" key really ends up being used as the termination key.
1.2467 - */
1.2468 - if( btmLimit ){
1.2469 - Expr *pX;
1.2470 - int k = pIdx->aiColumn[j];
1.2471 - pTerm = findTerm(&wc, iCur, k, notReady, btmOp, pIdx);
1.2472 - assert( pTerm!=0 );
1.2473 - pX = pTerm->pExpr;
1.2474 - assert( (pTerm->flags & TERM_CODED)==0 );
1.2475 - sqlite3ExprCode(pParse, pX->pRight);
1.2476 - sqlite3VdbeAddOp(v, OP_IsNull, -(nEq+1), nxt);
1.2477 - btmEq = pTerm->eOperator & (WO_LE|WO_GE);
1.2478 - disableTerm(pLevel, pTerm);
1.2479 - }else{
1.2480 - btmEq = 1;
1.2481 - }
1.2482 - if( nEq>0 || btmLimit ){
1.2483 - int nCol = nEq + btmLimit;
1.2484 - buildIndexProbe(v, nCol, pIdx);
1.2485 - if( bRev ){
1.2486 - pLevel->iMem = pParse->nMem++;
1.2487 - sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
1.2488 - testOp = OP_IdxLT;
1.2489 - }else{
1.2490 - int op = btmEq ? OP_MoveGe : OP_MoveGt;
1.2491 - sqlite3VdbeAddOp(v, op, iIdxCur, nxt);
1.2492 - }
1.2493 - }else if( bRev ){
1.2494 - testOp = OP_Noop;
1.2495 - }else{
1.2496 - sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, brk);
1.2497 - }
1.2498 -
1.2499 - /* Generate the the top of the loop. If there is a termination
1.2500 - ** key we have to test for that key and abort at the top of the
1.2501 - ** loop.
1.2502 - */
1.2503 - start = sqlite3VdbeCurrentAddr(v);
1.2504 - if( testOp!=OP_Noop ){
1.2505 - sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
1.2506 - sqlite3VdbeAddOp(v, testOp, iIdxCur, nxt);
1.2507 - if( (topEq && !bRev) || (!btmEq && bRev) ){
1.2508 - sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC);
1.2509 - }
1.2510 - }
1.2511 - if( topLimit | btmLimit ){
1.2512 - sqlite3VdbeAddOp(v, OP_Column, iIdxCur, nEq);
1.2513 - sqlite3VdbeAddOp(v, OP_IsNull, 1, cont);
1.2514 - }
1.2515 - if( !omitTable ){
1.2516 - sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
1.2517 - sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
1.2518 - }
1.2519 -
1.2520 - /* Record the instruction used to terminate the loop.
1.2521 - */
1.2522 - pLevel->op = bRev ? OP_Prev : OP_Next;
1.2523 - pLevel->p1 = iIdxCur;
1.2524 - pLevel->p2 = start;
1.2525 - }else if( pLevel->flags & WHERE_COLUMN_EQ ){
1.2526 - /* Case 4: There is an index and all terms of the WHERE clause that
1.2527 - ** refer to the index using the "==" or "IN" operators.
1.2528 - */
1.2529 - int start;
1.2530 - int nEq = pLevel->nEq;
1.2531 -
1.2532 - /* Generate code to evaluate all constraint terms using == or IN
1.2533 - ** and leave the values of those terms on the stack.
1.2534 - */
1.2535 - codeAllEqualityTerms(pParse, pLevel, &wc, notReady);
1.2536 - nxt = pLevel->nxt;
1.2537 -
1.2538 - /* Generate a single key that will be used to both start and terminate
1.2539 - ** the search
1.2540 - */
1.2541 - buildIndexProbe(v, nEq, pIdx);
1.2542 - sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0);
1.2543 -
1.2544 - /* Generate code (1) to move to the first matching element of the table.
1.2545 - ** Then generate code (2) that jumps to "nxt" after the cursor is past
1.2546 - ** the last matching element of the table. The code (1) is executed
1.2547 - ** once to initialize the search, the code (2) is executed before each
1.2548 - ** iteration of the scan to see if the scan has finished. */
1.2549 - if( bRev ){
1.2550 - /* Scan in reverse order */
1.2551 - sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, nxt);
1.2552 - start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
1.2553 - sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, nxt);
1.2554 - pLevel->op = OP_Prev;
1.2555 - }else{
1.2556 - /* Scan in the forward order */
1.2557 - sqlite3VdbeAddOp(v, OP_MoveGe, iIdxCur, nxt);
1.2558 - start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
1.2559 - sqlite3VdbeOp3(v, OP_IdxGE, iIdxCur, nxt, "+", P3_STATIC);
1.2560 - pLevel->op = OP_Next;
1.2561 - }
1.2562 - if( !omitTable ){
1.2563 - sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
1.2564 - sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
1.2565 - }
1.2566 - pLevel->p1 = iIdxCur;
1.2567 - pLevel->p2 = start;
1.2568 - }else{
1.2569 - /* Case 5: There is no usable index. We must do a complete
1.2570 - ** scan of the entire table.
1.2571 - */
1.2572 - assert( omitTable==0 );
1.2573 - assert( bRev==0 );
1.2574 - pLevel->op = OP_Next;
1.2575 - pLevel->p1 = iCur;
1.2576 - pLevel->p2 = 1 + sqlite3VdbeAddOp(v, OP_Rewind, iCur, brk);
1.2577 - }
1.2578 - notReady &= ~getMask(&maskSet, iCur);
1.2579 -
1.2580 - /* Insert code to test every subexpression that can be completely
1.2581 - ** computed using the current set of tables.
1.2582 - */
1.2583 - for(pTerm=wc.a, j=wc.nTerm; j>0; j--, pTerm++){
1.2584 - Expr *pE;
1.2585 - if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
1.2586 - if( (pTerm->prereqAll & notReady)!=0 ) continue;
1.2587 - pE = pTerm->pExpr;
1.2588 - assert( pE!=0 );
1.2589 - if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
1.2590 - continue;
1.2591 - }
1.2592 - sqlite3ExprIfFalse(pParse, pE, cont, 1);
1.2593 - pTerm->flags |= TERM_CODED;
1.2594 - }
1.2595 -
1.2596 - /* For a LEFT OUTER JOIN, generate code that will record the fact that
1.2597 - ** at least one row of the right table has matched the left table.
1.2598 - */
1.2599 - if( pLevel->iLeftJoin ){
1.2600 - pLevel->top = sqlite3VdbeCurrentAddr(v);
1.2601 - sqlite3VdbeAddOp(v, OP_MemInt, 1, pLevel->iLeftJoin);
1.2602 - VdbeComment((v, "# record LEFT JOIN hit"));
1.2603 - for(pTerm=wc.a, j=0; j<wc.nTerm; j++, pTerm++){
1.2604 - if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
1.2605 - if( (pTerm->prereqAll & notReady)!=0 ) continue;
1.2606 - assert( pTerm->pExpr );
1.2607 - sqlite3ExprIfFalse(pParse, pTerm->pExpr, cont, 1);
1.2608 - pTerm->flags |= TERM_CODED;
1.2609 - }
1.2610 - }
1.2611 - }
1.2612 -
1.2613 -#ifdef SQLITE_TEST /* For testing and debugging use only */
1.2614 - /* Record in the query plan information about the current table
1.2615 - ** and the index used to access it (if any). If the table itself
1.2616 - ** is not used, its name is just '{}'. If no index is used
1.2617 - ** the index is listed as "{}". If the primary key is used the
1.2618 - ** index name is '*'.
1.2619 - */
1.2620 - for(i=0; i<pTabList->nSrc; i++){
1.2621 - char *z;
1.2622 - int n;
1.2623 - pLevel = &pWInfo->a[i];
1.2624 - pTabItem = &pTabList->a[pLevel->iFrom];
1.2625 - z = pTabItem->zAlias;
1.2626 - if( z==0 ) z = pTabItem->pTab->zName;
1.2627 - n = strlen(z);
1.2628 - if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
1.2629 - if( pLevel->flags & WHERE_IDX_ONLY ){
1.2630 - memcpy(&sqlite3_query_plan[nQPlan], "{}", 2);
1.2631 - nQPlan += 2;
1.2632 - }else{
1.2633 - memcpy(&sqlite3_query_plan[nQPlan], z, n);
1.2634 - nQPlan += n;
1.2635 - }
1.2636 - sqlite3_query_plan[nQPlan++] = ' ';
1.2637 - }
1.2638 - if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
1.2639 - memcpy(&sqlite3_query_plan[nQPlan], "* ", 2);
1.2640 - nQPlan += 2;
1.2641 - }else if( pLevel->pIdx==0 ){
1.2642 - memcpy(&sqlite3_query_plan[nQPlan], "{} ", 3);
1.2643 - nQPlan += 3;
1.2644 - }else{
1.2645 - n = strlen(pLevel->pIdx->zName);
1.2646 - if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
1.2647 - memcpy(&sqlite3_query_plan[nQPlan], pLevel->pIdx->zName, n);
1.2648 - nQPlan += n;
1.2649 - sqlite3_query_plan[nQPlan++] = ' ';
1.2650 - }
1.2651 - }
1.2652 - }
1.2653 - while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
1.2654 - sqlite3_query_plan[--nQPlan] = 0;
1.2655 - }
1.2656 - sqlite3_query_plan[nQPlan] = 0;
1.2657 - nQPlan = 0;
1.2658 -#endif /* SQLITE_TEST // Testing and debugging use only */
1.2659 -
1.2660 - /* Record the continuation address in the WhereInfo structure. Then
1.2661 - ** clean up and return.
1.2662 - */
1.2663 - pWInfo->iContinue = cont;
1.2664 - whereClauseClear(&wc);
1.2665 - return pWInfo;
1.2666 -
1.2667 - /* Jump here if malloc fails */
1.2668 -whereBeginNoMem:
1.2669 - whereClauseClear(&wc);
1.2670 - whereInfoFree(pWInfo);
1.2671 - return 0;
1.2672 -}
1.2673 -
1.2674 -/*
1.2675 -** Generate the end of the WHERE loop. See comments on
1.2676 -** sqlite3WhereBegin() for additional information.
1.2677 -*/
1.2678 -void sqlite3WhereEnd(WhereInfo *pWInfo){
1.2679 - Vdbe *v = pWInfo->pParse->pVdbe;
1.2680 - int i;
1.2681 - WhereLevel *pLevel;
1.2682 - SrcList *pTabList = pWInfo->pTabList;
1.2683 -
1.2684 - /* Generate loop termination code.
1.2685 - */
1.2686 - for(i=pTabList->nSrc-1; i>=0; i--){
1.2687 - pLevel = &pWInfo->a[i];
1.2688 - sqlite3VdbeResolveLabel(v, pLevel->cont);
1.2689 - if( pLevel->op!=OP_Noop ){
1.2690 - sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2);
1.2691 - }
1.2692 - if( pLevel->nIn ){
1.2693 - struct InLoop *pIn;
1.2694 - int j;
1.2695 - sqlite3VdbeResolveLabel(v, pLevel->nxt);
1.2696 - for(j=pLevel->nIn, pIn=&pLevel->aInLoop[j-1]; j>0; j--, pIn--){
1.2697 - sqlite3VdbeJumpHere(v, pIn->topAddr+1);
1.2698 - sqlite3VdbeAddOp(v, OP_Next, pIn->iCur, pIn->topAddr);
1.2699 - sqlite3VdbeJumpHere(v, pIn->topAddr-1);
1.2700 - }
1.2701 - sqlite3_free(pLevel->aInLoop);
1.2702 - }
1.2703 - sqlite3VdbeResolveLabel(v, pLevel->brk);
1.2704 - if( pLevel->iLeftJoin ){
1.2705 - int addr;
1.2706 - addr = sqlite3VdbeAddOp(v, OP_IfMemPos, pLevel->iLeftJoin, 0);
1.2707 - sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0);
1.2708 - if( pLevel->iIdxCur>=0 ){
1.2709 - sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iIdxCur, 0);
1.2710 - }
1.2711 - sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top);
1.2712 - sqlite3VdbeJumpHere(v, addr);
1.2713 - }
1.2714 - }
1.2715 -
1.2716 - /* The "break" point is here, just past the end of the outer loop.
1.2717 - ** Set it.
1.2718 - */
1.2719 - sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
1.2720 -
1.2721 - /* Close all of the cursors that were opened by sqlite3WhereBegin.
1.2722 - */
1.2723 - for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
1.2724 - struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
1.2725 - Table *pTab = pTabItem->pTab;
1.2726 - assert( pTab!=0 );
1.2727 - if( pTab->isEphem || pTab->pSelect ) continue;
1.2728 - if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
1.2729 - sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
1.2730 - }
1.2731 - if( pLevel->pIdx!=0 ){
1.2732 - sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0);
1.2733 - }
1.2734 -
1.2735 - /* Make cursor substitutions for cases where we want to use
1.2736 - ** just the index and never reference the table.
1.2737 - **
1.2738 - ** Calls to the code generator in between sqlite3WhereBegin and
1.2739 - ** sqlite3WhereEnd will have created code that references the table
1.2740 - ** directly. This loop scans all that code looking for opcodes
1.2741 - ** that reference the table and converts them into opcodes that
1.2742 - ** reference the index.
1.2743 - */
1.2744 - if( pLevel->flags & WHERE_IDX_ONLY ){
1.2745 - int k, j, last;
1.2746 - VdbeOp *pOp;
1.2747 - Index *pIdx = pLevel->pIdx;
1.2748 -
1.2749 - assert( pIdx!=0 );
1.2750 - pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
1.2751 - last = sqlite3VdbeCurrentAddr(v);
1.2752 - for(k=pWInfo->iTop; k<last; k++, pOp++){
1.2753 - if( pOp->p1!=pLevel->iTabCur ) continue;
1.2754 - if( pOp->opcode==OP_Column ){
1.2755 - pOp->p1 = pLevel->iIdxCur;
1.2756 - for(j=0; j<pIdx->nColumn; j++){
1.2757 - if( pOp->p2==pIdx->aiColumn[j] ){
1.2758 - pOp->p2 = j;
1.2759 - break;
1.2760 - }
1.2761 - }
1.2762 - }else if( pOp->opcode==OP_Rowid ){
1.2763 - pOp->p1 = pLevel->iIdxCur;
1.2764 - pOp->opcode = OP_IdxRowid;
1.2765 - }else if( pOp->opcode==OP_NullRow ){
1.2766 - pOp->opcode = OP_Noop;
1.2767 - }
1.2768 - }
1.2769 - }
1.2770 - }
1.2771 -
1.2772 - /* Final cleanup
1.2773 - */
1.2774 - whereInfoFree(pWInfo);
1.2775 - return;
1.2776 -}
