1.1 --- a/extensions/sqlite/sqlite-source/btreeInt.h Sun Oct 28 05:06:12 2007 +0000
1.2 +++ b/extensions/sqlite/sqlite-source/btreeInt.h Sun Oct 28 05:48:06 2007 +0000
1.3 @@ -248,7 +248,7 @@
1.4
1.5 /*
1.6 ** Page type flags. An ORed combination of these flags appear as the
1.7 -** first byte of every BTree page.
1.8 +** first byte of on-disk image of every BTree page.
1.9 */
1.10 #define PTF_INTKEY 0x01
1.11 #define PTF_ZERODATA 0x02
1.12 @@ -264,6 +264,9 @@
1.13 ** walk up the BTree from any leaf to the root. Care must be taken to
1.14 ** unref() the parent page pointer when this page is no longer referenced.
1.15 ** The pageDestructor() routine handles that chore.
1.16 +**
1.17 +** Access to all fields of this structure is controlled by the mutex
1.18 +** stored in MemPage.pBt->mutex.
1.19 */
1.20 struct MemPage {
1.21 u8 isInit; /* True if previously initialized. MUST BE FIRST! */
1.22 @@ -276,8 +279,8 @@
1.23 u8 hasData; /* True if this page stores data */
1.24 u8 hdrOffset; /* 100 for page 1. 0 otherwise */
1.25 u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */
1.26 - u16 maxLocal; /* Copy of Btree.maxLocal or Btree.maxLeaf */
1.27 - u16 minLocal; /* Copy of Btree.minLocal or Btree.minLeaf */
1.28 + u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
1.29 + u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */
1.30 u16 cellOffset; /* Index in aData of first cell pointer */
1.31 u16 idxParent; /* Index in parent of this node */
1.32 u16 nFree; /* Number of free bytes on the page */
1.33 @@ -286,8 +289,8 @@
1.34 u8 *pCell; /* Pointers to the body of the overflow cell */
1.35 u16 idx; /* Insert this cell before idx-th non-overflow cell */
1.36 } aOvfl[5];
1.37 - BtShared *pBt; /* Pointer back to BTree structure */
1.38 - u8 *aData; /* Pointer back to the start of the page */
1.39 + BtShared *pBt; /* Pointer to BtShared that this page is part of */
1.40 + u8 *aData; /* Pointer to disk image of the page data */
1.41 DbPage *pDbPage; /* Pager page handle */
1.42 Pgno pgno; /* Page number for this page */
1.43 MemPage *pParent; /* The parent of this page. NULL for root */
1.44 @@ -300,11 +303,36 @@
1.45 */
1.46 #define EXTRA_SIZE sizeof(MemPage)
1.47
1.48 -/* Btree handle */
1.49 +/* A Btree handle
1.50 +**
1.51 +** A database connection contains a pointer to an instance of
1.52 +** this object for every database file that it has open. This structure
1.53 +** is opaque to the database connection. The database connection cannot
1.54 +** see the internals of this structure and only deals with pointers to
1.55 +** this structure.
1.56 +**
1.57 +** For some database files, the same underlying database cache might be
1.58 +** shared between multiple connections. In that case, each contection
1.59 +** has it own pointer to this object. But each instance of this object
1.60 +** points to the same BtShared object. The database cache and the
1.61 +** schema associated with the database file are all contained within
1.62 +** the BtShared object.
1.63 +**
1.64 +** All fields in this structure are accessed under sqlite3.mutex.
1.65 +** The pBt pointer itself may not be changed while there exists cursors
1.66 +** in the referenced BtShared that point back to this Btree since those
1.67 +** cursors have to do go through this Btree to find their BtShared and
1.68 +** they often do so without holding sqlite3.mutex.
1.69 +*/
1.70 struct Btree {
1.71 - sqlite3 *pSqlite;
1.72 - BtShared *pBt;
1.73 - u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
1.74 + sqlite3 *pSqlite; /* The database connection holding this btree */
1.75 + BtShared *pBt; /* Sharable content of this btree */
1.76 + u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
1.77 + u8 sharable; /* True if we can share pBt with other pSqlite */
1.78 + u8 locked; /* True if pSqlite currently has pBt locked */
1.79 + int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */
1.80 + Btree *pNext; /* List of other sharable Btrees from the same pSqlite */
1.81 + Btree *pPrev; /* Back pointer of the same list */
1.82 };
1.83
1.84 /*
1.85 @@ -312,15 +340,28 @@
1.86 **
1.87 ** If the shared-data extension is enabled, there may be multiple users
1.88 ** of the Btree structure. At most one of these may open a write transaction,
1.89 -** but any number may have active read transactions. Variable Btree.pDb
1.90 -** points to the handle that owns any current write-transaction.
1.91 +** but any number may have active read transactions.
1.92 */
1.93 #define TRANS_NONE 0
1.94 #define TRANS_READ 1
1.95 #define TRANS_WRITE 2
1.96
1.97 /*
1.98 -** Everything we need to know about an open database
1.99 +** An instance of this object represents a single database file.
1.100 +**
1.101 +** A single database file can be in use as the same time by two
1.102 +** or more database connections. When two or more connections are
1.103 +** sharing the same database file, each connection has it own
1.104 +** private Btree object for the file and each of those Btrees points
1.105 +** to this one BtShared object. BtShared.nRef is the number of
1.106 +** connections currently sharing this database file.
1.107 +**
1.108 +** Fields in this structure are accessed under the BtShared.mutex
1.109 +** mutex, except for nRef and pNext which are accessed under the
1.110 +** global SQLITE_MUTEX_STATIC_MASTER mutex. The pPager field
1.111 +** may not be modified once it is initially set as long as nRef>0.
1.112 +** The pSchema field may be set once under BtShared.mutex and
1.113 +** thereafter is unchanged as long as nRef>0.
1.114 */
1.115 struct BtShared {
1.116 Pager *pPager; /* The page cache */
1.117 @@ -345,13 +386,14 @@
1.118 int minLeaf; /* Minimum local payload in a LEAFDATA table */
1.119 BusyHandler *pBusyHandler; /* Callback for when there is lock contention */
1.120 u8 inTransaction; /* Transaction state */
1.121 - int nRef; /* Number of references to this structure */
1.122 int nTransaction; /* Number of open transactions (read + write) */
1.123 void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */
1.124 void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */
1.125 + sqlite3_mutex *mutex; /* Non-recursive mutex required to access this struct */
1.126 #ifndef SQLITE_OMIT_SHARED_CACHE
1.127 + int nRef; /* Number of references to this structure */
1.128 + BtShared *pNext; /* Next on a list of sharable BtShared structs */
1.129 BtLock *pLock; /* List of locks held on this shared-btree struct */
1.130 - BtShared *pNext; /* Next in ThreadData.pBtree linked list */
1.131 #endif
1.132 };
1.133
1.134 @@ -373,12 +415,22 @@
1.135 };
1.136
1.137 /*
1.138 -** A cursor is a pointer to a particular entry in the BTree.
1.139 +** A cursor is a pointer to a particular entry within a particular
1.140 +** b-tree within a database file.
1.141 +**
1.142 ** The entry is identified by its MemPage and the index in
1.143 ** MemPage.aCell[] of the entry.
1.144 +**
1.145 +** When a single database file can shared by two more database connections,
1.146 +** but cursors cannot be shared. Each cursor is associated with a
1.147 +** particular database connection identified BtCursor.pBtree.pSqlite.
1.148 +**
1.149 +** Fields in this structure are accessed under the BtShared.mutex
1.150 +** found at self->pBt->mutex.
1.151 */
1.152 struct BtCursor {
1.153 Btree *pBtree; /* The Btree to which this cursor belongs */
1.154 + BtShared *pBt; /* The BtShared this cursor points to */
1.155 BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */
1.156 int (*xCompare)(void*,int,const void*,int,const void*); /* Key comp func */
1.157 void *pArg; /* First arg to xCompare() */
1.158 @@ -414,10 +466,18 @@
1.159 ** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in
1.160 ** this state, restoreOrClearCursorPosition() can be called to attempt to
1.161 ** seek the cursor to the saved position.
1.162 +**
1.163 +** CURSOR_FAULT:
1.164 +** A unrecoverable error (an I/O error or a malloc failure) has occurred
1.165 +** on a different connection that shares the BtShared cache with this
1.166 +** cursor. The error has left the cache in an inconsistent state.
1.167 +** Do nothing else with this cursor. Any attempt to use the cursor
1.168 +** should return the error code stored in BtCursor.skip
1.169 */
1.170 #define CURSOR_INVALID 0
1.171 #define CURSOR_VALID 1
1.172 #define CURSOR_REQUIRESEEK 2
1.173 +#define CURSOR_FAULT 3
1.174
1.175 /*
1.176 ** The TRACE macro will print high-level status information about the
1.177 @@ -530,8 +590,6 @@
1.178 ** of handle p (type Btree*) are internally consistent.
1.179 */
1.180 #define btreeIntegrity(p) \
1.181 - assert( p->inTrans!=TRANS_NONE || p->pBt->nTransaction<p->pBt->nRef ); \
1.182 - assert( p->pBt->nTransaction<=p->pBt->nRef ); \
1.183 assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \
1.184 assert( p->pBt->inTransaction>=p->inTrans );
1.185
1.186 @@ -580,7 +638,9 @@
1.187 int sqlite3BtreeInitPage(MemPage *pPage, MemPage *pParent);
1.188 void sqlite3BtreeParseCellPtr(MemPage*, u8*, CellInfo*);
1.189 void sqlite3BtreeParseCell(MemPage*, int, CellInfo*);
1.190 +#ifdef SQLITE_TEST
1.191 u8 *sqlite3BtreeFindCell(MemPage *pPage, int iCell);
1.192 +#endif
1.193 int sqlite3BtreeRestoreOrClearCursorPosition(BtCursor *pCur);
1.194 void sqlite3BtreeGetTempCursor(BtCursor *pCur, BtCursor *pTempCur);
1.195 void sqlite3BtreeReleaseTempCursor(BtCursor *pCur);
