database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-07-29 08:01:23 +03:00
Code Activity

Add code for the matchinfo 'longest common substring' feature.

Browse Source 
FossilOrigin-Name: 71011a4f9baf09ec6935ad591145252bf3c286ed
This commit is contained in:
dan
2010-11-24 19:26:18 +00:00
parent d6e12384bd
commit f9376540fa
6 changed files with 185 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

123
ext/fts3/fts3_snippet.c
View File

@ -970,7 +970,123 @@ static int fts3MatchinfoSelectDoctotal(
if( paLen ) *paLen = a;
return SQLITE_OK;
}
typedef struct LcsIterator LcsIterator;
struct LcsIterator {
Fts3Expr *pExpr; /* Pointer to phrase expression */
char *pRead; /* Cursor used to iterate through aDoclist */
int iPosOffset; /* Tokens count up to end of this phrase */
int iCol; /* Current column number */
int iPos; /* Current position */
};
#define LCS_ITERATOR_FINISHED 0x7FFFFFFF;
static int fts3MatchinfoLcsCb(
Fts3Expr *pExpr, /* Phrase expression node */
int iPhrase, /* Phrase number (numbered from zero) */
void *pCtx /* Pointer to MatchInfo structure */
){
LcsIterator *aIter = (LcsIterator *)pCtx;
aIter[iPhrase].pExpr = pExpr;
return SQLITE_OK;
}
static int fts3LcsIteratorAdvance(LcsIterator *pIter){
char *pRead = pIter->pRead;
sqlite3_int64 iRead;
int rc = 0;
pRead += sqlite3Fts3GetVarint(pRead, &iRead);
if( iRead==0 ){
pIter->iCol = LCS_ITERATOR_FINISHED;
rc = 1;
}else{
if( iRead==1 ){
pRead += sqlite3Fts3GetVarint(pRead, &iRead);
pIter->iCol = iRead;
pIter->iPos = pIter->iPosOffset;
pRead += sqlite3Fts3GetVarint(pRead, &iRead);
rc = 1;
}
pIter->iPos += (iRead-2);
}
pIter->pRead = pRead;
return rc;
}
static int fts3MatchinfoLcs(Fts3Cursor *pCsr, MatchInfo *pInfo){
LcsIterator *aIter;
int i;
int iCol;
int nToken = 0;
/* Allocate and populate the array of LcsIterator objects. The array
** contains one element for each matchable phrase in the query.
**/
aIter = sqlite3_malloc(sizeof(LcsIterator) * pCsr->nPhrase);
if( !aIter ) return SQLITE_NOMEM;
memset(aIter, 0, sizeof(LcsIterator) * pCsr->nPhrase);
(void)fts3ExprIterate(pCsr->pExpr, fts3MatchinfoLcsCb, (void*)aIter);
for(i=0; i<pInfo->nPhrase; i++){
LcsIterator *pIter = &aIter[i];
nToken -= pIter->pExpr->pPhrase->nToken;
pIter->iPosOffset = nToken;
pIter->pRead = sqlite3Fts3FindPositions(pIter->pExpr, pCsr->iPrevId, -1);
if( pIter->pRead ){
pIter->iPos = pIter->iPosOffset;
fts3LcsIteratorAdvance(&aIter[i]);
}else{
pIter->iCol = LCS_ITERATOR_FINISHED;
}
}
for(iCol=0; iCol<pInfo->nCol; iCol++){
int nLcs = 0;
int nLive = 0;
for(i=0; i<pInfo->nPhrase; i++){
assert( aIter[i].iCol>=iCol );
if( aIter[i].iCol==iCol ) nLive++;
}
while( nLive>0 ){
LcsIterator *pAdv = 0;
int nThisLcs = 0;
char *aRead;
sqlite3_int64 iRead;
for(i=0; i<pInfo->nPhrase; i++){
LcsIterator *pIter = &aIter[i];
int nToken = pIter->pExpr->pPhrase->nToken;
if( iCol!=pIter->iCol ){
nThisLcs = 0;
continue;
}
if( pAdv==0 || pIter->iPos<pAdv->iPos ){
pAdv = pIter;
}
if( nThisLcs==0 || pIter->iPos==pIter[-1].iPos ){
nThisLcs++;
}else{
nThisLcs = 1;
}
if( nThisLcs>nLcs ) nLcs = nThisLcs;
}
if( fts3LcsIteratorAdvance(pAdv) ) nLive--;
}
pInfo->aMatchinfo[iCol] = nLcs;
}
sqlite3_free(aIter);
}
static int fts3MatchinfoValues(
Fts3Cursor *pCsr, /* FTS3 cursor object */
@ -1048,9 +1164,12 @@ static int fts3MatchinfoValues(
break;
}
case FTS3_MATCHINFO_LCS:
fts3MatchinfoLcs(pCsr, pInfo);
break;
default:
assert( zArg[i]==FTS3_MATCHINFO_LCS );
default:
assert( !"this cannot happen" );
}
pInfo->aMatchinfo += fts3MatchinfoSize(pInfo, zArg[i]);