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.

FossilOrigin-Name: a518bc3318232d652349eb29303ff250aee40459

diff --git a/manifest b/manifest
index 3034b1c1804f1993e8581d0d0cade934eee79d4b..de67a3e45aba5acc9528262db0fbfcec4237084c 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C When\senlarging\sthe\ssize\sof\sa\sStrAccum\sobject,\suse\ssqlite3DbMallocSize()\sto\nrecord\sthe\sentire\ssize\sof\sthe\sallocation,\snot\sjust\sthe\srequested\ssize.
-D 2014-11-03T13:24:12.668
+C Use\sexponential\sbuffer\ssize\sgrowth\sin\sStrAccum,\sas\slong\sas\sthe\ssize\sdoes\snot\ngrow\sto\slarge,\sto\savoid\sexcess\smemory\sallocation\sresize\soperations.\s\sAlso,\ndocument\sthe\sfact\sthat\ssetting\sscratch\smemory\scauses\sSQLite\sto\stry\sto\savoid\nlarge\smemory\sallocations.
+D 2014-11-03T14:46:29.027
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in cf57f673d77606ab0f2d9627ca52a9ba1464146a
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -223,13 +223,13 @@ F src/pcache.h 9b559127b83f84ff76d735c8262f04853be0c59a
 F src/pcache1.c e412cb585f777c840ddce0500eddc5c6043c2bb5
 F src/pragma.c 3f3e959390a10c0131676f0e307acce372777e0f
 F src/prepare.c b7b7bf020bd4c962f7c8aed5a3c542c7dfe9f9c7
-F src/printf.c ee13daccd49ddf767d057bc98395c9e83d4e2067
+F src/printf.c 9e75a6a0b55bf61cfff7d7e19d89834a1b938236
 F src/random.c ba2679f80ec82c4190062d756f22d0c358180696
 F src/resolve.c 4965007d6497b6a4d7a6d98751cc39712885f952
 F src/rowset.c eccf6af6d620aaa4579bd3b72c1b6395d9e9fa1e
 F src/select.c 428165951748151e87a15295b7357221433e311b
 F src/shell.c 282f8f5278e0c78eb442217531172ec9e1538796
-F src/sqlite.h.in c3c6180be49d91d3b0001a8d3c604684f361adc2
+F src/sqlite.h.in dd0cb63fb7cb558892afe8253c3279c508c50329
 F src/sqlite3.rc 992c9f5fb8285ae285d6be28240a7e8d3a7f2bad
 F src/sqlite3ext.h 17d487c3c91b0b8c584a32fbeb393f6f795eea7d
 F src/sqliteInt.h 8f67ca79e957b8ece7453b8e320b6a996e1b4761
@@ -296,7 +296,7 @@ F src/vdbeapi.c 02d8afcff710eb35e3d9e49cb677308296b00009
 F src/vdbeaux.c 3d6b2b412ef2193aa4729922dfc5df1efadbf6df
 F src/vdbeblob.c 8b5442ff0954c44b45cbabbe2e94091a2e16fdef
 F src/vdbemem.c 31d8eabb0cd78bfeab4e5124c7363c3e9e54db9f
-F src/vdbesort.c 975aeffa99acb0991b2f288d30294756bff41438
+F src/vdbesort.c daf87ea542df088ac4607660d09976d36b6bd95d
 F src/vdbetrace.c 7e4222955e07dd707a2f360c0eb73452be1cb010
 F src/vtab.c 2a30791bbd7926b589401bd09c3abb33de563793
 F src/wal.c 10e7de7ce90865a68153f001a61f1d985cd17983
@@ -1210,7 +1210,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 49188b2bb53a92b0b0b6aaf8247edeb0c1bcd1f5
-R 041ffec3947ff9e90700478ea54978f5
+P 3dda3c937469ce661d1cd0e8d8963a03e698ee39
+R e2c699e9cb6d832117ea76de0a03f26b
 U drh
-Z 42c888343c3ca87538d56b9b17ae76ab
+Z 91c9a2887aef0ce4f97740bae4c1a9ba

diff --git a/manifest.uuid b/manifest.uuid
index 8be6ab985634186ad4d1b8aa21cc4423eb895161..11815fb0c2d38c65584a2aedcdf3d82296d04be5 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-3dda3c937469ce661d1cd0e8d8963a03e698ee39
\ No newline at end of file
+a518bc3318232d652349eb29303ff250aee40459
\ No newline at end of file

diff --git a/src/printf.c b/src/printf.c
index e20619f9a715010d7634353d08df40af56fad227..ac7b0516314450947899517fc47d0ad07967ba8c 100644 (file)
--- a/src/printf.c
+++ b/src/printf.c
@@ -770,6 +770,11 @@ static int sqlite3StrAccumEnlarge(StrAccum *p, int N){
     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);

diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index d0f213f156f7c646e64ac01d34323bd235623721..ffd0ade039771886dfbef63731f87e4ca11670d0 100644 (file)
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -1535,8 +1535,7 @@ struct sqlite3_mem_methods {
 ** 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 sz
-** argument must be a multiple of 16.
+** 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
@@ -1548,7 +1547,13 @@ struct sqlite3_mem_methods {
 ** 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.</dd>
+** [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

diff --git a/src/vdbesort.c b/src/vdbesort.c
index 46c9f3789de323f2dbadda1fe902bf00f282a617..918d84071601d1accd5339dbb8a998ceeeb2cdad 100644 (file)
--- a/src/vdbesort.c
+++ b/src/vdbesort.c
@@ -847,11 +847,9 @@ int sqlite3VdbeSorterInit(
       if( mxCache<SORTER_MIN_WORKING ) mxCache = SORTER_MIN_WORKING;
       pSorter->mxPmaSize = mxCache * pgsz;
 
-      /* If the application has not configure scratch memory using
-      ** SQLITE_CONFIG_SCRATCH then we assume it is OK to do large memory
-      ** allocations.  If scratch memory has been configured, then assume
-      ** large memory allocations should be avoided to prevent heap
-      ** fragmentation.
+      /* 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 );