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First attempt at enhancing the "PRAGMA cache_spill" statement to accept a

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cache threashold size.

FossilOrigin-Name: 549d42be0dac87dc04c3eeccfdc60615c3a6ad3f
This commit is contained in:
drh
2015-11-12 14:57:19 +00:00
parent 3d38cec99a
commit 9b0cf34f81
12 changed files with 257 additions and 140 deletions
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38
src/btree.c
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@@ -2556,19 +2556,11 @@ int sqlite3BtreeClose(Btree *p){
}
/*
** Change the limit on the number of pages allowed in the cache.
**
** The maximum number of cache pages is set to the absolute
** value of mxPage. If mxPage is negative, the pager will
** operate asynchronously - it will not stop to do fsync()s
** to insure data is written to the disk surface before
** continuing. Transactions still work if synchronous is off,
** and the database cannot be corrupted if this program
** crashes. But if the operating system crashes or there is
** an abrupt power failure when synchronous is off, the database
** could be left in an inconsistent and unrecoverable state.
** Synchronous is on by default so database corruption is not
** normally a worry.
** Change the "soft" limit on the number of pages in the cache.
** Unused and unmodified pages will be recycled when the number of
** pages in the cache exceeds this soft limit. But the size of the
** cache is allowed to grow larger than this limit if it contains
** dirty pages or pages still in active use.
*/
int sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
BtShared *pBt = p->pBt;
@@ -2579,6 +2571,26 @@ int sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
return SQLITE_OK;
}
/*
** Change the "spill" limit on the number of pages in the cache.
** If the number of pages exceeds this limit during a write transaction,
** the pager might attempt to "spill" pages to the journal early in
** order to free up memory.
**
** The value returned is the current spill size. If zero is passed
** as an argument, no changes are made to the spill size setting, so
** using mxPage of 0 is a way to query the current spill size.
*/
int sqlite3BtreeSetSpillSize(Btree *p, int mxPage){
BtShared *pBt = p->pBt;
int res;
assert( sqlite3_mutex_held(p->db->mutex) );
sqlite3BtreeEnter(p);
res = sqlite3PagerSetSpillsize(pBt->pPager, mxPage);
sqlite3BtreeLeave(p);
return res;
}
#if SQLITE_MAX_MMAP_SIZE>0
/*
** Change the limit on the amount of the database file that may be