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Overview
| Comment: | Use exponential buffer size growth in StrAccum, as long as the size does not grow to large, to avoid excess memory allocation resize operations. Also, document the fact that setting scratch memory causes SQLite to try to avoid large memory allocations. |
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| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
a518bc3318232d652349eb29303ff250 |
| User & Date: | drh 2014-11-03 14:46:29.027 |
Context
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2014-11-03
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| 16:56 | Add the experimental sqlite3_stmt_scanstatus() API. For comparing the number of rows actually visited by a loop with the estimate used by the query planner. (check-in: ab3b0fc576 user: dan tags: trunk) | |
| 14:46 | Use exponential buffer size growth in StrAccum, as long as the size does not grow to large, to avoid excess memory allocation resize operations. Also, document the fact that setting scratch memory causes SQLite to try to avoid large memory allocations. (check-in: a518bc3318 user: drh tags: trunk) | |
| 13:24 | When enlarging the size of a StrAccum object, use sqlite3DbMallocSize() to record the entire size of the allocation, not just the requested size. (check-in: 3dda3c9374 user: drh tags: trunk) | |
Changes
Changes to src/printf.c.
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766 767 768 769 770 771 772 773 774 775 776 777 778 779 |
N = p->nAlloc - p->nChar - 1;
setStrAccumError(p, STRACCUM_TOOBIG);
return N;
}else{
char *zOld = (p->zText==p->zBase ? 0 : p->zText);
i64 szNew = p->nChar;
szNew += N + 1;
if( szNew > p->mxAlloc ){
sqlite3StrAccumReset(p);
setStrAccumError(p, STRACCUM_TOOBIG);
return 0;
}else{
p->nAlloc = (int)szNew;
}
| > > > > > | 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 |
N = p->nAlloc - p->nChar - 1;
setStrAccumError(p, STRACCUM_TOOBIG);
return N;
}else{
char *zOld = (p->zText==p->zBase ? 0 : p->zText);
i64 szNew = p->nChar;
szNew += N + 1;
if( szNew+p->nChar<=p->mxAlloc ){
/* Force exponential buffer size growth as long as it does not overflow,
** to avoid having to call this routine too often */
szNew += p->nChar;
}
if( szNew > p->mxAlloc ){
sqlite3StrAccumReset(p);
setStrAccumError(p, STRACCUM_TOOBIG);
return 0;
}else{
p->nAlloc = (int)szNew;
}
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Changes to src/sqlite.h.in.
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1531 1532 1533 1534 1535 1536 1537 | ** </dd> ** ** [[SQLITE_CONFIG_SCRATCH]] <dt>SQLITE_CONFIG_SCRATCH</dt> ** <dd> ^This option specifies a static memory buffer that SQLite can use for ** scratch memory. ^(There are three arguments: A pointer an 8-byte ** aligned memory buffer from which the scratch allocations will be ** drawn, the size of each scratch allocation (sz), | | < | > > > > > > | 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 | ** </dd> ** ** [[SQLITE_CONFIG_SCRATCH]] <dt>SQLITE_CONFIG_SCRATCH</dt> ** <dd> ^This option specifies a static memory buffer that SQLite can use for ** scratch memory. ^(There are three arguments: A pointer an 8-byte ** aligned memory buffer from which the scratch allocations will be ** drawn, the size of each scratch allocation (sz), ** and the maximum number of scratch allocations (N).)^ ** The first argument must be a pointer to an 8-byte aligned buffer ** of at least sz*N bytes of memory. ** ^SQLite will not use more than two scratch buffers per thread and not ** more than one scratch buffer per thread when not performing ** a [checkpoint] in [WAL mode]. ** ^SQLite will never request a scratch buffer that is more than 6 ** times the database page size, except when performing a [checkpoint] ** in [WAL mode] when the scratch buffer request size is a small fraction ** of the size of the WAL file. ** ^If SQLite needs needs additional ** scratch memory beyond what is provided by this configuration option, then ** [sqlite3_malloc()] will be used to obtain the memory needed.<p> ** ^When the application provides any amount of scratch memory using ** SQLITE_CONFIG_SCRATCH, SQLite avoids unnecessary large ** [sqlite3_malloc|heap allocations]. ** This can help [Robson proof|prevent memory allocation failures] due to heap ** fragmentation in low-memory embedded systems. ** </dd> ** ** [[SQLITE_CONFIG_PAGECACHE]] <dt>SQLITE_CONFIG_PAGECACHE</dt> ** <dd> ^This option specifies a static memory buffer that SQLite can use for ** the database page cache with the default page cache implementation. ** This configuration should not be used if an application-define page ** cache implementation is loaded using the SQLITE_CONFIG_PCACHE2 option. ** There are three arguments to this option: A pointer to 8-byte aligned |
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Changes to src/vdbesort.c.
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843 844 845 846 847 848 849 |
if( !sqlite3TempInMemory(db) ){
pSorter->mnPmaSize = SORTER_MIN_WORKING * pgsz;
mxCache = db->aDb[0].pSchema->cache_size;
if( mxCache<SORTER_MIN_WORKING ) mxCache = SORTER_MIN_WORKING;
pSorter->mxPmaSize = mxCache * pgsz;
| | | < | < | 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 |
if( !sqlite3TempInMemory(db) ){
pSorter->mnPmaSize = SORTER_MIN_WORKING * pgsz;
mxCache = db->aDb[0].pSchema->cache_size;
if( mxCache<SORTER_MIN_WORKING ) mxCache = SORTER_MIN_WORKING;
pSorter->mxPmaSize = mxCache * pgsz;
/* EVIDENCE-OF: R-26747-61719 When the application provides any amount of
** scratch memory using SQLITE_CONFIG_SCRATCH, SQLite avoids unnecessary
** large heap allocations.
*/
if( sqlite3GlobalConfig.pScratch==0 ){
assert( pSorter->iMemory==0 );
pSorter->nMemory = pgsz;
pSorter->list.aMemory = (u8*)sqlite3Malloc(pgsz);
if( !pSorter->list.aMemory ) rc = SQLITE_NOMEM;
}
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