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Move the rowid cache out of VdbeCursor and into BtCursor. When multiple

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BtCursors are open on the same table, set their rowid cache all at the
same time.  Ticket #3731. (CVS 6354)

FossilOrigin-Name: 189785832a7dc9f4a0a2113d850b92b987e0f9bf
This commit is contained in:
drh
2009-03-17 22:33:00 +00:00
parent 21822c58b0
commit 7f75122149
8 changed files with 125 additions and 34 deletions
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52
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.573 2009/03/16 13:19:36 danielk1977 Exp $
** $Id: btree.c,v 1.574 2009/03/17 22:33:01 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
@@ -1764,6 +1764,12 @@ int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve){
int sqlite3BtreeGetPageSize(Btree *p){
return p->pBt->pageSize;
}
/*
** Return the number of bytes of space at the end of every page that
** are intentually left unused. This is the "reserved" space that is
** sometimes used by extensions.
*/
int sqlite3BtreeGetReserve(Btree *p){
int n;
sqlite3BtreeEnter(p);
@@ -3005,6 +3011,7 @@ static int btreeCursor(
}
pBt->pCursor = pCur;
pCur->eState = CURSOR_INVALID;
pCur->cachedRowid = 0;
return SQLITE_OK;
@@ -3027,11 +3034,48 @@ int sqlite3BtreeCursor(
sqlite3BtreeLeave(p);
return rc;
}
int sqlite3BtreeCursorSize(){
/*
** Return the size of a BtCursor object in bytes.
**
** This interfaces is needed so that users of cursors can preallocate
** sufficient storage to hold a cursor. The BtCursor object is opaque
** to users so they cannot do the sizeof() themselves - they must call
** this routine.
*/
int sqlite3BtreeCursorSize(void){
return sizeof(BtCursor);
}
/*
** Set the cached rowid value of every cursor in the same database file
** as pCur and having the same root page number as pCur. The value is
** set to iRowid.
**
** Only positive rowid values are considered valid for this cache.
** The cache is initialized to zero, indicating an invalid cache.
** A btree will work fine with zero or negative rowids. We just cannot
** cache zero or negative rowids, which means tables that use zero or
** negative rowids might run a little slower. But in practice, zero
** or negative rowids are very uncommon so this should not be a problem.
*/
void sqlite3BtreeSetCachedRowid(BtCursor *pCur, sqlite3_int64 iRowid){
BtCursor *p;
for(p=pCur->pBt->pCursor; p; p=p->pNext){
if( p->pgnoRoot==pCur->pgnoRoot ) p->cachedRowid = iRowid;
}
assert( pCur->cachedRowid==iRowid );
}
/*
** Return the cached rowid for the given cursor. A negative or zero
** return value indicates that the rowid cache is invalid and should be
** ignored. If the rowid cache has never before been set, then a
** zero is returned.
*/
sqlite3_int64 sqlite3BtreeGetCachedRowid(BtCursor *pCur){
return pCur->cachedRowid;
}
/*
** Close a cursor. The read lock on the database file is released
@@ -3093,6 +3137,8 @@ void sqlite3BtreeReleaseTempCursor(BtCursor *pCur){
sqlite3_free(pCur->pKey);
}
/*
** Make sure the BtCursor* given in the argument has a valid
** BtCursor.info structure. If it is not already valid, call
@@ -3530,7 +3576,7 @@ int sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
** and data to fit on the local page and for there to be no overflow
** pages. When that is so, this routine can be used to access the
** key and data without making a copy. If the key and/or data spills
** onto overflow pages, then accessPayload() must be used to reassembly
** onto overflow pages, then accessPayload() must be used to reassemble
** the key/data and copy it into a preallocated buffer.
**
** The pointer returned by this routine looks directly into the cached