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Re-introduce the prefix-search optimization of [feef1b15d6], which was lost in a reorganization of FTS3 code.

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FossilOrigin-Name: d692434b4935e8e7858230af1c126b0be8203077
This commit is contained in:
dan
2010-07-19 11:16:36 +00:00
parent bd0c001405
commit a69f7d5aa5
6 changed files with 157 additions and 96 deletions
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128
ext/fts3/fts3.c
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@ -1621,10 +1621,58 @@ static int fts3DoclistMerge(
typedef struct TermSelect TermSelect;
struct TermSelect {
int isReqPos;
char *aOutput; /* Malloc'd output buffer */
int nOutput; /* Size of output in bytes */
char *aaOutput[16]; /* Malloc'd output buffer */
int anOutput[16]; /* Size of output in bytes */
};
/*
** Merge all doclists in the TermSelect.aaOutput[] array into a single
** doclist stored in TermSelect.aaOutput[0]. If successful, delete all
** other doclists (except the aaOutput[0] one) and return SQLITE_OK.
**
** If an OOM error occurs, return SQLITE_NOMEM. In this case it is
** the responsibility of the caller to free any doclists left in the
** TermSelect.aaOutput[] array.
*/
static int fts3TermSelectMerge(TermSelect *pTS){
int mergetype = (pTS->isReqPos ? MERGE_POS_OR : MERGE_OR);
char *aOut = 0;
int nOut = 0;
int i;
/* Loop through the doclists in the aaOutput[] array. Merge them all
** into a single doclist.
*/
for(i=0; i<SizeofArray(pTS->aaOutput); i++){
if( pTS->aaOutput[i] ){
if( !aOut ){
aOut = pTS->aaOutput[i];
nOut = pTS->anOutput[i];
pTS->aaOutput[0] = 0;
}else{
int nNew = nOut + pTS->anOutput[i];
char *aNew = sqlite3_malloc(nNew);
if( !aNew ){
sqlite3_free(aOut);
return SQLITE_NOMEM;
}
fts3DoclistMerge(mergetype, 0, 0,
aNew, &nNew, pTS->aaOutput[i], pTS->anOutput[i], aOut, nOut
);
sqlite3_free(pTS->aaOutput[i]);
sqlite3_free(aOut);
pTS->aaOutput[i] = 0;
aOut = aNew;
nOut = nNew;
}
}
}
pTS->aaOutput[0] = aOut;
pTS->anOutput[0] = nOut;
return SQLITE_OK;
}
/*
** This function is used as the sqlite3Fts3SegReaderIterate() callback when
** querying the full-text index for a doclist associated with a term or
@ -1639,38 +1687,63 @@ static int fts3TermSelectCb(
int nDoclist
){
TermSelect *pTS = (TermSelect *)pContext;
int nNew = pTS->nOutput + nDoclist;
char *aNew = sqlite3_malloc(nNew);
UNUSED_PARAMETER(p);
UNUSED_PARAMETER(zTerm);
UNUSED_PARAMETER(nTerm);
if( !aNew ){
return SQLITE_NOMEM;
}
if( pTS->nOutput==0 ){
if( pTS->aaOutput[0]==0 ){
/* If this is the first term selected, copy the doclist to the output
** buffer using memcpy(). TODO: Add a way to transfer control of the
** aDoclist buffer from the caller so as to avoid the memcpy().
*/
memcpy(aNew, aDoclist, nDoclist);
pTS->aaOutput[0] = sqlite3_malloc(nDoclist);
pTS->anOutput[0] = nDoclist;
if( pTS->aaOutput[0] ){
memcpy(pTS->aaOutput[0], aDoclist, nDoclist);
}else{
return SQLITE_NOMEM;
}
}else{
/* The output buffer is not empty. Merge doclist aDoclist with the
** existing output. This can only happen with prefix-searches (as
** searches for exact terms return exactly one doclist).
*/
int mergetype = (pTS->isReqPos ? MERGE_POS_OR : MERGE_OR);
fts3DoclistMerge(mergetype, 0, 0,
aNew, &nNew, pTS->aOutput, pTS->nOutput, aDoclist, nDoclist
);
char *aMerge = aDoclist;
int nMerge = nDoclist;
int iOut;
for(iOut=0; iOut<SizeofArray(pTS->aaOutput); iOut++){
char *aNew;
int nNew;
if( pTS->aaOutput[iOut]==0 ){
assert( iOut>0 );
pTS->aaOutput[iOut] = aMerge;
pTS->anOutput[iOut] = nMerge;
break;
}
nNew = nMerge + pTS->anOutput[iOut];
aNew = sqlite3_malloc(nNew);
if( !aNew ){
if( aMerge!=aDoclist ){
sqlite3_free(aMerge);
}
return SQLITE_NOMEM;
}
fts3DoclistMerge(mergetype, 0, 0,
aNew, &nNew, pTS->aaOutput[iOut], pTS->anOutput[iOut], aMerge, nMerge
);
if( iOut>0 ) sqlite3_free(aMerge);
sqlite3_free(pTS->aaOutput[iOut]);
pTS->aaOutput[iOut] = 0;
aMerge = aNew;
nMerge = nNew;
if( (iOut+1)==SizeofArray(pTS->aaOutput) ){
pTS->aaOutput[iOut] = aMerge;
pTS->anOutput[iOut] = nMerge;
}
}
}
sqlite3_free(pTS->aOutput);
pTS->aOutput = aNew;
pTS->nOutput = nNew;
return SQLITE_OK;
}
@ -1794,12 +1867,17 @@ static int fts3TermSelect(
rc = sqlite3Fts3SegReaderIterate(p, apSegment, nSegment, &filter,
fts3TermSelectCb, (void *)&tsc
);
if( rc==SQLITE_OK ){
rc = fts3TermSelectMerge(&tsc);
}
if( rc==SQLITE_OK ){
*ppOut = tsc.aOutput;
*pnOut = tsc.nOutput;
*ppOut = tsc.aaOutput[0];
*pnOut = tsc.anOutput[0];
}else{
sqlite3_free(tsc.aOutput);
for(i=0; i<SizeofArray(tsc.aaOutput); i++){
sqlite3_free(tsc.aaOutput[i]);
}
}
finished: