database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-10-21 11:13:54 +03:00
Code Activity

Improve the performance of the built-in REPLACE() function in cases where

Browse Source 
it does many substitutions that make the string larger.  OSSFuzz is reporting
intermittant timeouts when running a test where it does a REPLACE() on a 
930KB random blob. Perhaps this enhancement will fix that.

FossilOrigin-Name: fab2c2b07b5d3cd851db3e6f5c8a44155e32b0df22905ea33412b153b825a928
This commit is contained in:
drh
2018-02-09 23:25:14 +00:00
parent 510fea885e
commit f313952097
4 changed files with 45 additions and 25 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
src/func.c
View File

@@ -1199,6 +1199,8 @@ static void replaceFunc(
i64 nOut; /* Maximum size of zOut */
int loopLimit; /* Last zStr[] that might match zPattern[] */
int i, j; /* Loop counters */
unsigned cntExpand; /* Number zOut expansions */
sqlite3 *db = sqlite3_context_db_handle(context);
assert( argc==3 );
UNUSED_PARAMETER(argc);
@@ -1230,33 +1232,40 @@ static void replaceFunc(
return;
}
loopLimit = nStr - nPattern;
cntExpand = 0;
for(i=j=0; i<=loopLimit; i++){
if( zStr[i]!=zPattern[0] || memcmp(&zStr[i], zPattern, nPattern) ){
zOut[j++] = zStr[i];
}else{
u8 *zOld;
sqlite3 *db = sqlite3_context_db_handle(context);
nOut += nRep - nPattern;
testcase( nOut-1==db->aLimit[SQLITE_LIMIT_LENGTH] );
testcase( nOut-2==db->aLimit[SQLITE_LIMIT_LENGTH] );
if( nOut-1>db->aLimit[SQLITE_LIMIT_LENGTH] ){
sqlite3_result_error_toobig(context);
sqlite3_free(zOut);
return;
}
zOld = zOut;
zOut = sqlite3_realloc64(zOut, (int)nOut);
if( zOut==0 ){
sqlite3_result_error_nomem(context);
sqlite3_free(zOld);
return;
if( nRep>nPattern ){
nOut += nRep - nPattern;
if( nOut-1>db->aLimit[SQLITE_LIMIT_LENGTH] ){
sqlite3_result_error_toobig(context);
sqlite3_free(zOut);
return;
}
testcase( nOut-1==db->aLimit[SQLITE_LIMIT_LENGTH] );
testcase( nOut-2==db->aLimit[SQLITE_LIMIT_LENGTH] );
cntExpand++;
if( (cntExpand&(cntExpand-1))==0 ){
/* Grow the size of the output buffer only on substitutions
** whose index is a power of two: 1, 2, 4, 8, 16, 32, ... */
u8 *zOld;
zOld = zOut;
zOut = sqlite3_realloc64(zOut, (int)nOut + (nOut - nStr - 1));
if( zOut==0 ){
sqlite3_result_error_nomem(context);
sqlite3_free(zOld);
return;
}
}
}
memcpy(&zOut[j], zRep, nRep);
j += nRep;
i += nPattern-1;
}
}
assert( j+nStr-i+1==nOut );
assert( j+nStr-i+1<=nOut );
memcpy(&zOut[j], &zStr[i], nStr-i);
j += nStr - i;
assert( j<=nOut );