1.1 --- a/extensions/sqlite/sqlite-source/btreeInt.h Fri Jul 11 06:51:21 2008 +0000
1.2 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000
1.3 @@ -1,648 +0,0 @@
1.4 -/*
1.5 -** 2004 April 6
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 -** $Id$
1.16 -**
1.17 -** This file implements a external (disk-based) database using BTrees.
1.18 -** For a detailed discussion of BTrees, refer to
1.19 -**
1.20 -** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
1.21 -** "Sorting And Searching", pages 473-480. Addison-Wesley
1.22 -** Publishing Company, Reading, Massachusetts.
1.23 -**
1.24 -** The basic idea is that each page of the file contains N database
1.25 -** entries and N+1 pointers to subpages.
1.26 -**
1.27 -** ----------------------------------------------------------------
1.28 -** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) |
1.29 -** ----------------------------------------------------------------
1.30 -**
1.31 -** All of the keys on the page that Ptr(0) points to have values less
1.32 -** than Key(0). All of the keys on page Ptr(1) and its subpages have
1.33 -** values greater than Key(0) and less than Key(1). All of the keys
1.34 -** on Ptr(N) and its subpages have values greater than Key(N-1). And
1.35 -** so forth.
1.36 -**
1.37 -** Finding a particular key requires reading O(log(M)) pages from the
1.38 -** disk where M is the number of entries in the tree.
1.39 -**
1.40 -** In this implementation, a single file can hold one or more separate
1.41 -** BTrees. Each BTree is identified by the index of its root page. The
1.42 -** key and data for any entry are combined to form the "payload". A
1.43 -** fixed amount of payload can be carried directly on the database
1.44 -** page. If the payload is larger than the preset amount then surplus
1.45 -** bytes are stored on overflow pages. The payload for an entry
1.46 -** and the preceding pointer are combined to form a "Cell". Each
1.47 -** page has a small header which contains the Ptr(N) pointer and other
1.48 -** information such as the size of key and data.
1.49 -**
1.50 -** FORMAT DETAILS
1.51 -**
1.52 -** The file is divided into pages. The first page is called page 1,
1.53 -** the second is page 2, and so forth. A page number of zero indicates
1.54 -** "no such page". The page size can be anything between 512 and 65536.
1.55 -** Each page can be either a btree page, a freelist page or an overflow
1.56 -** page.
1.57 -**
1.58 -** The first page is always a btree page. The first 100 bytes of the first
1.59 -** page contain a special header (the "file header") that describes the file.
1.60 -** The format of the file header is as follows:
1.61 -**
1.62 -** OFFSET SIZE DESCRIPTION
1.63 -** 0 16 Header string: "SQLite format 3\000"
1.64 -** 16 2 Page size in bytes.
1.65 -** 18 1 File format write version
1.66 -** 19 1 File format read version
1.67 -** 20 1 Bytes of unused space at the end of each page
1.68 -** 21 1 Max embedded payload fraction
1.69 -** 22 1 Min embedded payload fraction
1.70 -** 23 1 Min leaf payload fraction
1.71 -** 24 4 File change counter
1.72 -** 28 4 Reserved for future use
1.73 -** 32 4 First freelist page
1.74 -** 36 4 Number of freelist pages in the file
1.75 -** 40 60 15 4-byte meta values passed to higher layers
1.76 -**
1.77 -** All of the integer values are big-endian (most significant byte first).
1.78 -**
1.79 -** The file change counter is incremented when the database is changed
1.80 -** This counter allows other processes to know when the file has changed
1.81 -** and thus when they need to flush their cache.
1.82 -**
1.83 -** The max embedded payload fraction is the amount of the total usable
1.84 -** space in a page that can be consumed by a single cell for standard
1.85 -** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default
1.86 -** is to limit the maximum cell size so that at least 4 cells will fit
1.87 -** on one page. Thus the default max embedded payload fraction is 64.
1.88 -**
1.89 -** If the payload for a cell is larger than the max payload, then extra
1.90 -** payload is spilled to overflow pages. Once an overflow page is allocated,
1.91 -** as many bytes as possible are moved into the overflow pages without letting
1.92 -** the cell size drop below the min embedded payload fraction.
1.93 -**
1.94 -** The min leaf payload fraction is like the min embedded payload fraction
1.95 -** except that it applies to leaf nodes in a LEAFDATA tree. The maximum
1.96 -** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
1.97 -** not specified in the header.
1.98 -**
1.99 -** Each btree pages is divided into three sections: The header, the
1.100 -** cell pointer array, and the cell content area. Page 1 also has a 100-byte
1.101 -** file header that occurs before the page header.
1.102 -**
1.103 -** |----------------|
1.104 -** | file header | 100 bytes. Page 1 only.
1.105 -** |----------------|
1.106 -** | page header | 8 bytes for leaves. 12 bytes for interior nodes
1.107 -** |----------------|
1.108 -** | cell pointer | | 2 bytes per cell. Sorted order.
1.109 -** | array | | Grows downward
1.110 -** | | v
1.111 -** |----------------|
1.112 -** | unallocated |
1.113 -** | space |
1.114 -** |----------------| ^ Grows upwards
1.115 -** | cell content | | Arbitrary order interspersed with freeblocks.
1.116 -** | area | | and free space fragments.
1.117 -** |----------------|
1.118 -**
1.119 -** The page headers looks like this:
1.120 -**
1.121 -** OFFSET SIZE DESCRIPTION
1.122 -** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
1.123 -** 1 2 byte offset to the first freeblock
1.124 -** 3 2 number of cells on this page
1.125 -** 5 2 first byte of the cell content area
1.126 -** 7 1 number of fragmented free bytes
1.127 -** 8 4 Right child (the Ptr(N) value). Omitted on leaves.
1.128 -**
1.129 -** The flags define the format of this btree page. The leaf flag means that
1.130 -** this page has no children. The zerodata flag means that this page carries
1.131 -** only keys and no data. The intkey flag means that the key is a integer
1.132 -** which is stored in the key size entry of the cell header rather than in
1.133 -** the payload area.
1.134 -**
1.135 -** The cell pointer array begins on the first byte after the page header.
1.136 -** The cell pointer array contains zero or more 2-byte numbers which are
1.137 -** offsets from the beginning of the page to the cell content in the cell
1.138 -** content area. The cell pointers occur in sorted order. The system strives
1.139 -** to keep free space after the last cell pointer so that new cells can
1.140 -** be easily added without having to defragment the page.
1.141 -**
1.142 -** Cell content is stored at the very end of the page and grows toward the
1.143 -** beginning of the page.
1.144 -**
1.145 -** Unused space within the cell content area is collected into a linked list of
1.146 -** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset
1.147 -** to the first freeblock is given in the header. Freeblocks occur in
1.148 -** increasing order. Because a freeblock must be at least 4 bytes in size,
1.149 -** any group of 3 or fewer unused bytes in the cell content area cannot
1.150 -** exist on the freeblock chain. A group of 3 or fewer free bytes is called
1.151 -** a fragment. The total number of bytes in all fragments is recorded.
1.152 -** in the page header at offset 7.
1.153 -**
1.154 -** SIZE DESCRIPTION
1.155 -** 2 Byte offset of the next freeblock
1.156 -** 2 Bytes in this freeblock
1.157 -**
1.158 -** Cells are of variable length. Cells are stored in the cell content area at
1.159 -** the end of the page. Pointers to the cells are in the cell pointer array
1.160 -** that immediately follows the page header. Cells is not necessarily
1.161 -** contiguous or in order, but cell pointers are contiguous and in order.
1.162 -**
1.163 -** Cell content makes use of variable length integers. A variable
1.164 -** length integer is 1 to 9 bytes where the lower 7 bits of each
1.165 -** byte are used. The integer consists of all bytes that have bit 8 set and
1.166 -** the first byte with bit 8 clear. The most significant byte of the integer
1.167 -** appears first. A variable-length integer may not be more than 9 bytes long.
1.168 -** As a special case, all 8 bytes of the 9th byte are used as data. This
1.169 -** allows a 64-bit integer to be encoded in 9 bytes.
1.170 -**
1.171 -** 0x00 becomes 0x00000000
1.172 -** 0x7f becomes 0x0000007f
1.173 -** 0x81 0x00 becomes 0x00000080
1.174 -** 0x82 0x00 becomes 0x00000100
1.175 -** 0x80 0x7f becomes 0x0000007f
1.176 -** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678
1.177 -** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081
1.178 -**
1.179 -** Variable length integers are used for rowids and to hold the number of
1.180 -** bytes of key and data in a btree cell.
1.181 -**
1.182 -** The content of a cell looks like this:
1.183 -**
1.184 -** SIZE DESCRIPTION
1.185 -** 4 Page number of the left child. Omitted if leaf flag is set.
1.186 -** var Number of bytes of data. Omitted if the zerodata flag is set.
1.187 -** var Number of bytes of key. Or the key itself if intkey flag is set.
1.188 -** * Payload
1.189 -** 4 First page of the overflow chain. Omitted if no overflow
1.190 -**
1.191 -** Overflow pages form a linked list. Each page except the last is completely
1.192 -** filled with data (pagesize - 4 bytes). The last page can have as little
1.193 -** as 1 byte of data.
1.194 -**
1.195 -** SIZE DESCRIPTION
1.196 -** 4 Page number of next overflow page
1.197 -** * Data
1.198 -**
1.199 -** Freelist pages come in two subtypes: trunk pages and leaf pages. The
1.200 -** file header points to the first in a linked list of trunk page. Each trunk
1.201 -** page points to multiple leaf pages. The content of a leaf page is
1.202 -** unspecified. A trunk page looks like this:
1.203 -**
1.204 -** SIZE DESCRIPTION
1.205 -** 4 Page number of next trunk page
1.206 -** 4 Number of leaf pointers on this page
1.207 -** * zero or more pages numbers of leaves
1.208 -*/
1.209 -#include "sqliteInt.h"
1.210 -#include "pager.h"
1.211 -#include "btree.h"
1.212 -#include "os.h"
1.213 -#include <assert.h>
1.214 -
1.215 -/* Round up a number to the next larger multiple of 8. This is used
1.216 -** to force 8-byte alignment on 64-bit architectures.
1.217 -*/
1.218 -#define ROUND8(x) ((x+7)&~7)
1.219 -
1.220 -
1.221 -/* The following value is the maximum cell size assuming a maximum page
1.222 -** size give above.
1.223 -*/
1.224 -#define MX_CELL_SIZE(pBt) (pBt->pageSize-8)
1.225 -
1.226 -/* The maximum number of cells on a single page of the database. This
1.227 -** assumes a minimum cell size of 3 bytes. Such small cells will be
1.228 -** exceedingly rare, but they are possible.
1.229 -*/
1.230 -#define MX_CELL(pBt) ((pBt->pageSize-8)/3)
1.231 -
1.232 -/* Forward declarations */
1.233 -typedef struct MemPage MemPage;
1.234 -typedef struct BtLock BtLock;
1.235 -
1.236 -/*
1.237 -** This is a magic string that appears at the beginning of every
1.238 -** SQLite database in order to identify the file as a real database.
1.239 -**
1.240 -** You can change this value at compile-time by specifying a
1.241 -** -DSQLITE_FILE_HEADER="..." on the compiler command-line. The
1.242 -** header must be exactly 16 bytes including the zero-terminator so
1.243 -** the string itself should be 15 characters long. If you change
1.244 -** the header, then your custom library will not be able to read
1.245 -** databases generated by the standard tools and the standard tools
1.246 -** will not be able to read databases created by your custom library.
1.247 -*/
1.248 -#ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
1.249 -# define SQLITE_FILE_HEADER "SQLite format 3"
1.250 -#endif
1.251 -
1.252 -/*
1.253 -** Page type flags. An ORed combination of these flags appear as the
1.254 -** first byte of on-disk image of every BTree page.
1.255 -*/
1.256 -#define PTF_INTKEY 0x01
1.257 -#define PTF_ZERODATA 0x02
1.258 -#define PTF_LEAFDATA 0x04
1.259 -#define PTF_LEAF 0x08
1.260 -
1.261 -/*
1.262 -** As each page of the file is loaded into memory, an instance of the following
1.263 -** structure is appended and initialized to zero. This structure stores
1.264 -** information about the page that is decoded from the raw file page.
1.265 -**
1.266 -** The pParent field points back to the parent page. This allows us to
1.267 -** walk up the BTree from any leaf to the root. Care must be taken to
1.268 -** unref() the parent page pointer when this page is no longer referenced.
1.269 -** The pageDestructor() routine handles that chore.
1.270 -**
1.271 -** Access to all fields of this structure is controlled by the mutex
1.272 -** stored in MemPage.pBt->mutex.
1.273 -*/
1.274 -struct MemPage {
1.275 - u8 isInit; /* True if previously initialized. MUST BE FIRST! */
1.276 - u8 idxShift; /* True if Cell indices have changed */
1.277 - u8 nOverflow; /* Number of overflow cell bodies in aCell[] */
1.278 - u8 intKey; /* True if intkey flag is set */
1.279 - u8 leaf; /* True if leaf flag is set */
1.280 - u8 zeroData; /* True if table stores keys only */
1.281 - u8 leafData; /* True if tables stores data on leaves only */
1.282 - u8 hasData; /* True if this page stores data */
1.283 - u8 hdrOffset; /* 100 for page 1. 0 otherwise */
1.284 - u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */
1.285 - u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
1.286 - u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */
1.287 - u16 cellOffset; /* Index in aData of first cell pointer */
1.288 - u16 idxParent; /* Index in parent of this node */
1.289 - u16 nFree; /* Number of free bytes on the page */
1.290 - u16 nCell; /* Number of cells on this page, local and ovfl */
1.291 - struct _OvflCell { /* Cells that will not fit on aData[] */
1.292 - u8 *pCell; /* Pointers to the body of the overflow cell */
1.293 - u16 idx; /* Insert this cell before idx-th non-overflow cell */
1.294 - } aOvfl[5];
1.295 - BtShared *pBt; /* Pointer to BtShared that this page is part of */
1.296 - u8 *aData; /* Pointer to disk image of the page data */
1.297 - DbPage *pDbPage; /* Pager page handle */
1.298 - Pgno pgno; /* Page number for this page */
1.299 - MemPage *pParent; /* The parent of this page. NULL for root */
1.300 -};
1.301 -
1.302 -/*
1.303 -** The in-memory image of a disk page has the auxiliary information appended
1.304 -** to the end. EXTRA_SIZE is the number of bytes of space needed to hold
1.305 -** that extra information.
1.306 -*/
1.307 -#define EXTRA_SIZE sizeof(MemPage)
1.308 -
1.309 -/* A Btree handle
1.310 -**
1.311 -** A database connection contains a pointer to an instance of
1.312 -** this object for every database file that it has open. This structure
1.313 -** is opaque to the database connection. The database connection cannot
1.314 -** see the internals of this structure and only deals with pointers to
1.315 -** this structure.
1.316 -**
1.317 -** For some database files, the same underlying database cache might be
1.318 -** shared between multiple connections. In that case, each contection
1.319 -** has it own pointer to this object. But each instance of this object
1.320 -** points to the same BtShared object. The database cache and the
1.321 -** schema associated with the database file are all contained within
1.322 -** the BtShared object.
1.323 -**
1.324 -** All fields in this structure are accessed under sqlite3.mutex.
1.325 -** The pBt pointer itself may not be changed while there exists cursors
1.326 -** in the referenced BtShared that point back to this Btree since those
1.327 -** cursors have to do go through this Btree to find their BtShared and
1.328 -** they often do so without holding sqlite3.mutex.
1.329 -*/
1.330 -struct Btree {
1.331 - sqlite3 *pSqlite; /* The database connection holding this btree */
1.332 - BtShared *pBt; /* Sharable content of this btree */
1.333 - u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
1.334 - u8 sharable; /* True if we can share pBt with other pSqlite */
1.335 - u8 locked; /* True if pSqlite currently has pBt locked */
1.336 - int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */
1.337 - Btree *pNext; /* List of other sharable Btrees from the same pSqlite */
1.338 - Btree *pPrev; /* Back pointer of the same list */
1.339 -};
1.340 -
1.341 -/*
1.342 -** Btree.inTrans may take one of the following values.
1.343 -**
1.344 -** If the shared-data extension is enabled, there may be multiple users
1.345 -** of the Btree structure. At most one of these may open a write transaction,
1.346 -** but any number may have active read transactions.
1.347 -*/
1.348 -#define TRANS_NONE 0
1.349 -#define TRANS_READ 1
1.350 -#define TRANS_WRITE 2
1.351 -
1.352 -/*
1.353 -** An instance of this object represents a single database file.
1.354 -**
1.355 -** A single database file can be in use as the same time by two
1.356 -** or more database connections. When two or more connections are
1.357 -** sharing the same database file, each connection has it own
1.358 -** private Btree object for the file and each of those Btrees points
1.359 -** to this one BtShared object. BtShared.nRef is the number of
1.360 -** connections currently sharing this database file.
1.361 -**
1.362 -** Fields in this structure are accessed under the BtShared.mutex
1.363 -** mutex, except for nRef and pNext which are accessed under the
1.364 -** global SQLITE_MUTEX_STATIC_MASTER mutex. The pPager field
1.365 -** may not be modified once it is initially set as long as nRef>0.
1.366 -** The pSchema field may be set once under BtShared.mutex and
1.367 -** thereafter is unchanged as long as nRef>0.
1.368 -*/
1.369 -struct BtShared {
1.370 - Pager *pPager; /* The page cache */
1.371 - BtCursor *pCursor; /* A list of all open cursors */
1.372 - MemPage *pPage1; /* First page of the database */
1.373 - u8 inStmt; /* True if we are in a statement subtransaction */
1.374 - u8 readOnly; /* True if the underlying file is readonly */
1.375 - u8 maxEmbedFrac; /* Maximum payload as % of total page size */
1.376 - u8 minEmbedFrac; /* Minimum payload as % of total page size */
1.377 - u8 minLeafFrac; /* Minimum leaf payload as % of total page size */
1.378 - u8 pageSizeFixed; /* True if the page size can no longer be changed */
1.379 -#ifndef SQLITE_OMIT_AUTOVACUUM
1.380 - u8 autoVacuum; /* True if auto-vacuum is enabled */
1.381 - u8 incrVacuum; /* True if incr-vacuum is enabled */
1.382 - Pgno nTrunc; /* Non-zero if the db will be truncated (incr vacuum) */
1.383 -#endif
1.384 - u16 pageSize; /* Total number of bytes on a page */
1.385 - u16 usableSize; /* Number of usable bytes on each page */
1.386 - int maxLocal; /* Maximum local payload in non-LEAFDATA tables */
1.387 - int minLocal; /* Minimum local payload in non-LEAFDATA tables */
1.388 - int maxLeaf; /* Maximum local payload in a LEAFDATA table */
1.389 - int minLeaf; /* Minimum local payload in a LEAFDATA table */
1.390 - BusyHandler *pBusyHandler; /* Callback for when there is lock contention */
1.391 - u8 inTransaction; /* Transaction state */
1.392 - int nTransaction; /* Number of open transactions (read + write) */
1.393 - void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */
1.394 - void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */
1.395 - sqlite3_mutex *mutex; /* Non-recursive mutex required to access this struct */
1.396 -#ifndef SQLITE_OMIT_SHARED_CACHE
1.397 - int nRef; /* Number of references to this structure */
1.398 - BtShared *pNext; /* Next on a list of sharable BtShared structs */
1.399 - BtLock *pLock; /* List of locks held on this shared-btree struct */
1.400 -#endif
1.401 -};
1.402 -
1.403 -/*
1.404 -** An instance of the following structure is used to hold information
1.405 -** about a cell. The parseCellPtr() function fills in this structure
1.406 -** based on information extract from the raw disk page.
1.407 -*/
1.408 -typedef struct CellInfo CellInfo;
1.409 -struct CellInfo {
1.410 - u8 *pCell; /* Pointer to the start of cell content */
1.411 - i64 nKey; /* The key for INTKEY tables, or number of bytes in key */
1.412 - u32 nData; /* Number of bytes of data */
1.413 - u32 nPayload; /* Total amount of payload */
1.414 - u16 nHeader; /* Size of the cell content header in bytes */
1.415 - u16 nLocal; /* Amount of payload held locally */
1.416 - u16 iOverflow; /* Offset to overflow page number. Zero if no overflow */
1.417 - u16 nSize; /* Size of the cell content on the main b-tree page */
1.418 -};
1.419 -
1.420 -/*
1.421 -** A cursor is a pointer to a particular entry within a particular
1.422 -** b-tree within a database file.
1.423 -**
1.424 -** The entry is identified by its MemPage and the index in
1.425 -** MemPage.aCell[] of the entry.
1.426 -**
1.427 -** When a single database file can shared by two more database connections,
1.428 -** but cursors cannot be shared. Each cursor is associated with a
1.429 -** particular database connection identified BtCursor.pBtree.pSqlite.
1.430 -**
1.431 -** Fields in this structure are accessed under the BtShared.mutex
1.432 -** found at self->pBt->mutex.
1.433 -*/
1.434 -struct BtCursor {
1.435 - Btree *pBtree; /* The Btree to which this cursor belongs */
1.436 - BtShared *pBt; /* The BtShared this cursor points to */
1.437 - BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */
1.438 - int (*xCompare)(void*,int,const void*,int,const void*); /* Key comp func */
1.439 - void *pArg; /* First arg to xCompare() */
1.440 - Pgno pgnoRoot; /* The root page of this tree */
1.441 - MemPage *pPage; /* Page that contains the entry */
1.442 - int idx; /* Index of the entry in pPage->aCell[] */
1.443 - CellInfo info; /* A parse of the cell we are pointing at */
1.444 - u8 wrFlag; /* True if writable */
1.445 - u8 eState; /* One of the CURSOR_XXX constants (see below) */
1.446 - void *pKey; /* Saved key that was cursor's last known position */
1.447 - i64 nKey; /* Size of pKey, or last integer key */
1.448 - int skip; /* (skip<0) -> Prev() is a no-op. (skip>0) -> Next() is */
1.449 -#ifndef SQLITE_OMIT_INCRBLOB
1.450 - u8 isIncrblobHandle; /* True if this cursor is an incr. io handle */
1.451 - Pgno *aOverflow; /* Cache of overflow page locations */
1.452 -#endif
1.453 -};
1.454 -
1.455 -/*
1.456 -** Potential values for BtCursor.eState.
1.457 -**
1.458 -** CURSOR_VALID:
1.459 -** Cursor points to a valid entry. getPayload() etc. may be called.
1.460 -**
1.461 -** CURSOR_INVALID:
1.462 -** Cursor does not point to a valid entry. This can happen (for example)
1.463 -** because the table is empty or because BtreeCursorFirst() has not been
1.464 -** called.
1.465 -**
1.466 -** CURSOR_REQUIRESEEK:
1.467 -** The table that this cursor was opened on still exists, but has been
1.468 -** modified since the cursor was last used. The cursor position is saved
1.469 -** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in
1.470 -** this state, restoreOrClearCursorPosition() can be called to attempt to
1.471 -** seek the cursor to the saved position.
1.472 -**
1.473 -** CURSOR_FAULT:
1.474 -** A unrecoverable error (an I/O error or a malloc failure) has occurred
1.475 -** on a different connection that shares the BtShared cache with this
1.476 -** cursor. The error has left the cache in an inconsistent state.
1.477 -** Do nothing else with this cursor. Any attempt to use the cursor
1.478 -** should return the error code stored in BtCursor.skip
1.479 -*/
1.480 -#define CURSOR_INVALID 0
1.481 -#define CURSOR_VALID 1
1.482 -#define CURSOR_REQUIRESEEK 2
1.483 -#define CURSOR_FAULT 3
1.484 -
1.485 -/*
1.486 -** The TRACE macro will print high-level status information about the
1.487 -** btree operation when the global variable sqlite3_btree_trace is
1.488 -** enabled.
1.489 -*/
1.490 -#if SQLITE_TEST
1.491 -# define TRACE(X) if( sqlite3_btree_trace ){ printf X; fflush(stdout); }
1.492 -#else
1.493 -# define TRACE(X)
1.494 -#endif
1.495 -
1.496 -/*
1.497 -** Routines to read and write variable-length integers. These used to
1.498 -** be defined locally, but now we use the varint routines in the util.c
1.499 -** file.
1.500 -*/
1.501 -#define getVarint sqlite3GetVarint
1.502 -#define getVarint32(A,B) ((*B=*(A))<=0x7f?1:sqlite3GetVarint32(A,B))
1.503 -#define putVarint sqlite3PutVarint
1.504 -
1.505 -/* The database page the PENDING_BYTE occupies. This page is never used.
1.506 -** TODO: This macro is very similary to PAGER_MJ_PGNO() in pager.c. They
1.507 -** should possibly be consolidated (presumably in pager.h).
1.508 -**
1.509 -** If disk I/O is omitted (meaning that the database is stored purely
1.510 -** in memory) then there is no pending byte.
1.511 -*/
1.512 -#ifdef SQLITE_OMIT_DISKIO
1.513 -# define PENDING_BYTE_PAGE(pBt) 0x7fffffff
1.514 -#else
1.515 -# define PENDING_BYTE_PAGE(pBt) ((PENDING_BYTE/(pBt)->pageSize)+1)
1.516 -#endif
1.517 -
1.518 -/*
1.519 -** A linked list of the following structures is stored at BtShared.pLock.
1.520 -** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor
1.521 -** is opened on the table with root page BtShared.iTable. Locks are removed
1.522 -** from this list when a transaction is committed or rolled back, or when
1.523 -** a btree handle is closed.
1.524 -*/
1.525 -struct BtLock {
1.526 - Btree *pBtree; /* Btree handle holding this lock */
1.527 - Pgno iTable; /* Root page of table */
1.528 - u8 eLock; /* READ_LOCK or WRITE_LOCK */
1.529 - BtLock *pNext; /* Next in BtShared.pLock list */
1.530 -};
1.531 -
1.532 -/* Candidate values for BtLock.eLock */
1.533 -#define READ_LOCK 1
1.534 -#define WRITE_LOCK 2
1.535 -
1.536 -/*
1.537 -** These macros define the location of the pointer-map entry for a
1.538 -** database page. The first argument to each is the number of usable
1.539 -** bytes on each page of the database (often 1024). The second is the
1.540 -** page number to look up in the pointer map.
1.541 -**
1.542 -** PTRMAP_PAGENO returns the database page number of the pointer-map
1.543 -** page that stores the required pointer. PTRMAP_PTROFFSET returns
1.544 -** the offset of the requested map entry.
1.545 -**
1.546 -** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
1.547 -** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
1.548 -** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
1.549 -** this test.
1.550 -*/
1.551 -#define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)
1.552 -#define PTRMAP_PTROFFSET(pBt, pgno) (5*(pgno-ptrmapPageno(pBt, pgno)-1))
1.553 -#define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))
1.554 -
1.555 -/*
1.556 -** The pointer map is a lookup table that identifies the parent page for
1.557 -** each child page in the database file. The parent page is the page that
1.558 -** contains a pointer to the child. Every page in the database contains
1.559 -** 0 or 1 parent pages. (In this context 'database page' refers
1.560 -** to any page that is not part of the pointer map itself.) Each pointer map
1.561 -** entry consists of a single byte 'type' and a 4 byte parent page number.
1.562 -** The PTRMAP_XXX identifiers below are the valid types.
1.563 -**
1.564 -** The purpose of the pointer map is to facility moving pages from one
1.565 -** position in the file to another as part of autovacuum. When a page
1.566 -** is moved, the pointer in its parent must be updated to point to the
1.567 -** new location. The pointer map is used to locate the parent page quickly.
1.568 -**
1.569 -** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
1.570 -** used in this case.
1.571 -**
1.572 -** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number
1.573 -** is not used in this case.
1.574 -**
1.575 -** PTRMAP_OVERFLOW1: The database page is the first page in a list of
1.576 -** overflow pages. The page number identifies the page that
1.577 -** contains the cell with a pointer to this overflow page.
1.578 -**
1.579 -** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
1.580 -** overflow pages. The page-number identifies the previous
1.581 -** page in the overflow page list.
1.582 -**
1.583 -** PTRMAP_BTREE: The database page is a non-root btree page. The page number
1.584 -** identifies the parent page in the btree.
1.585 -*/
1.586 -#define PTRMAP_ROOTPAGE 1
1.587 -#define PTRMAP_FREEPAGE 2
1.588 -#define PTRMAP_OVERFLOW1 3
1.589 -#define PTRMAP_OVERFLOW2 4
1.590 -#define PTRMAP_BTREE 5
1.591 -
1.592 -/* A bunch of assert() statements to check the transaction state variables
1.593 -** of handle p (type Btree*) are internally consistent.
1.594 -*/
1.595 -#define btreeIntegrity(p) \
1.596 - assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \
1.597 - assert( p->pBt->inTransaction>=p->inTrans );
1.598 -
1.599 -
1.600 -/*
1.601 -** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
1.602 -** if the database supports auto-vacuum or not. Because it is used
1.603 -** within an expression that is an argument to another macro
1.604 -** (sqliteMallocRaw), it is not possible to use conditional compilation.
1.605 -** So, this macro is defined instead.
1.606 -*/
1.607 -#ifndef SQLITE_OMIT_AUTOVACUUM
1.608 -#define ISAUTOVACUUM (pBt->autoVacuum)
1.609 -#else
1.610 -#define ISAUTOVACUUM 0
1.611 -#endif
1.612 -
1.613 -
1.614 -/*
1.615 -** This structure is passed around through all the sanity checking routines
1.616 -** in order to keep track of some global state information.
1.617 -*/
1.618 -typedef struct IntegrityCk IntegrityCk;
1.619 -struct IntegrityCk {
1.620 - BtShared *pBt; /* The tree being checked out */
1.621 - Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */
1.622 - int nPage; /* Number of pages in the database */
1.623 - int *anRef; /* Number of times each page is referenced */
1.624 - int mxErr; /* Stop accumulating errors when this reaches zero */
1.625 - char *zErrMsg; /* An error message. NULL if no errors seen. */
1.626 - int nErr; /* Number of messages written to zErrMsg so far */
1.627 -};
1.628 -
1.629 -/*
1.630 -** Read or write a two- and four-byte big-endian integer values.
1.631 -*/
1.632 -#define get2byte(x) ((x)[0]<<8 | (x)[1])
1.633 -#define put2byte(p,v) ((p)[0] = (v)>>8, (p)[1] = (v))
1.634 -#define get4byte sqlite3Get4byte
1.635 -#define put4byte sqlite3Put4byte
1.636 -
1.637 -/*
1.638 -** Internal routines that should be accessed by the btree layer only.
1.639 -*/
1.640 -int sqlite3BtreeGetPage(BtShared*, Pgno, MemPage**, int);
1.641 -int sqlite3BtreeInitPage(MemPage *pPage, MemPage *pParent);
1.642 -void sqlite3BtreeParseCellPtr(MemPage*, u8*, CellInfo*);
1.643 -void sqlite3BtreeParseCell(MemPage*, int, CellInfo*);
1.644 -#ifdef SQLITE_TEST
1.645 -u8 *sqlite3BtreeFindCell(MemPage *pPage, int iCell);
1.646 -#endif
1.647 -int sqlite3BtreeRestoreOrClearCursorPosition(BtCursor *pCur);
1.648 -void sqlite3BtreeGetTempCursor(BtCursor *pCur, BtCursor *pTempCur);
1.649 -void sqlite3BtreeReleaseTempCursor(BtCursor *pCur);
1.650 -int sqlite3BtreeIsRootPage(MemPage *pPage);
1.651 -void sqlite3BtreeMoveToParent(BtCursor *pCur);
