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Keep track of the optimal number of reserved bytes (by looking at reserve

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byte requests in calls to sqlite3BtreeSetPageSize()) and then change the
reserve byte count to the optimal when doing a VACUUM or when using the
backup API.

FossilOrigin-Name: 28c2b726285ea88b334acfd6390a057d2d244838
This commit is contained in:
drh
2015-02-21 00:19:25 +00:00
parent db222adfd3
commit ad0961b31b
9 changed files with 45 additions and 28 deletions
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23
src/btree.c
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@@ -2405,6 +2405,9 @@ int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve, int iFix){
BtShared *pBt = p->pBt;
assert( nReserve>=-1 && nReserve<=255 );
sqlite3BtreeEnter(p);
#if SQLITE_HAS_CODEC
if( nReserve>pBt->optimalReserve ) pBt->optimalReserve = (u8)nReserve;
#endif
if( pBt->btsFlags & BTS_PAGESIZE_FIXED ){
sqlite3BtreeLeave(p);
return SQLITE_READONLY;
@@ -2434,7 +2437,6 @@ int sqlite3BtreeGetPageSize(Btree *p){
return p->pBt->pageSize;
}
#if defined(SQLITE_HAS_CODEC) || defined(SQLITE_DEBUG)
/*
** This function is similar to sqlite3BtreeGetReserve(), except that it
** may only be called if it is guaranteed that the b-tree mutex is already
@@ -2447,25 +2449,33 @@ int sqlite3BtreeGetPageSize(Btree *p){
** database handle that owns *p, causing undefined behavior.
*/
int sqlite3BtreeGetReserveNoMutex(Btree *p){
int n;
assert( sqlite3_mutex_held(p->pBt->mutex) );
return p->pBt->pageSize - p->pBt->usableSize;
n = p->pBt->pageSize - p->pBt->usableSize;
return n;
}
#endif /* SQLITE_HAS_CODEC || SQLITE_DEBUG */
#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM)
/*
** 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.
**
** If SQLITE_HAS_MUTEX is defined then the number returned is the
** greater of the current reserved space and the maximum requested
** reserve space.
*/
int sqlite3BtreeGetReserve(Btree *p){
int sqlite3BtreeGetOptimalReserve(Btree *p){
int n;
sqlite3BtreeEnter(p);
n = p->pBt->pageSize - p->pBt->usableSize;
n = sqlite3BtreeGetReserveNoMutex(p);
#ifdef SQLITE_HAS_CODEC
if( n<p->pBt->optimalReserve ) n = p->pBt->optimalReserve;
#endif
sqlite3BtreeLeave(p);
return n;
}
/*
** Set the maximum page count for a database if mxPage is positive.
** No changes are made if mxPage is 0 or negative.
@@ -2496,7 +2506,6 @@ int sqlite3BtreeSecureDelete(Btree *p, int newFlag){
sqlite3BtreeLeave(p);
return b;
}
#endif /* !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM) */
/*
** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'