/* A helper function for mergeBlock(), below. Merge the position lists
* pointed to by m->in and pBlockReader.
* If the merge matches, write [iDocid] to m->pOut; if m->pOut
* has positions then write all matching positions as well. */
static void mergePosList(DocListMerge *m, sqlite_int64 iDocid,
DocListReader *pBlockReader){
int block_pos = readPosition(pBlockReader);
int in_pos = readPosition(&m->in);
int match = 0;
while( block_pos!=-1 || in_pos!=-1 ){
if( block_pos-m->iOffset==in_pos ){
if( !match ){
docListAddDocid(m->pOut, iDocid);
match = 1;
}
if( m->pOut->iType >= DL_POSITIONS ){
docListAddPos(m->pOut, in_pos);
}
block_pos = readPosition(pBlockReader);
in_pos = readPosition(&m->in);
} else if( in_pos==-1 || (block_pos!=-1 && block_pos-m->iOffset<in_pos) ){
block_pos = readPosition(pBlockReader);
} else {
in_pos = readPosition(&m->in);
}
}
if( m->pOut->iType >= DL_POSITIONS && match ){
docListAddEndPos(m->pOut);
}
}
/* Build a hash table containing all terms in zText. */
static int build_terms(Hash *terms, sqlite3_tokenizer *pTokenizer,
const char *zText, sqlite_int64 iDocid){
sqlite3_tokenizer_cursor *pCursor;
const char *pToken;
int nTokenBytes;
int iStartOffset, iEndOffset, iPosition;
int rc = pTokenizer->pModule->xOpen(pTokenizer, zText, -1, &pCursor);
if( rc!=SQLITE_OK ) return rc;
pCursor->pTokenizer = pTokenizer;
HashInit(terms, HASH_STRING, 1);
while( SQLITE_OK==pTokenizer->pModule->xNext(pCursor,
&pToken, &nTokenBytes,
&iStartOffset, &iEndOffset,
&iPosition) ){
DocList *p;
/* Positions can't be negative; we use -1 as a terminator internally. */
if( iPosition<0 ) {
rc = SQLITE_ERROR;
goto err;
}
p = HashFind(terms, pToken, nTokenBytes);
if( p==NULL ){
p = docListNew(DL_POSITIONS_OFFSETS);
docListAddDocid(p, iDocid);
HashInsert(terms, pToken, nTokenBytes, p);
}
docListAddPosOffset(p, iPosition, iStartOffset, iEndOffset);
}
err:
/* TODO(shess) Check return? Should this be able to cause errors at
** this point? Actually, same question about sqlite3_finalize(),
** though one could argue that failure there means that the data is
** not durable. *ponder*
*/
pTokenizer->pModule->xClose(pCursor);
return rc;
}
static int build_terms(Hash *terms, sqlite3_tokenizer *pTokenizer,
const char *zText, sqlite_int64 iDocid){
sqlite3_tokenizer_cursor *pCursor;
const char *pToken;
int nTokenBytes;
int iStartOffset, iEndOffset, iPosition;
int rc = pTokenizer->pModule->xOpen(pTokenizer, zText, -1, &pCursor);
if( rc!=SQLITE_OK ) return rc;
pCursor->pTokenizer = pTokenizer;
HashInit(terms, HASH_STRING, 1);
while( SQLITE_OK==pTokenizer->pModule->xNext(pCursor,
&pToken, &nTokenBytes,
&iStartOffset, &iEndOffset,
&iPosition) ){
DocList *p;
if( iPosition<0 ) {
rc = SQLITE_ERROR;
goto err;
}
p = HashFind(terms, pToken, nTokenBytes);
if( p==NULL ){
p = docListNew(DL_POSITIONS_OFFSETS);
docListAddDocid(p, iDocid);
HashInsert(terms, pToken, nTokenBytes, p);
}
docListAddPosOffset(p, iPosition, iStartOffset, iEndOffset);
}
err:
pTokenizer->pModule->xClose(pCursor);
return rc;
}
/* Merge one block of an on-disk doclist into a DocListMerge. */
static void mergeBlock(DocListMerge *m, DocList *pBlock){
DocListReader blockReader;
assert( pBlock->iType >= DL_POSITIONS );
readerInit(&blockReader, pBlock);
while( !readerAtEnd(&blockReader) ){
sqlite_int64 iDocid = readDocid(&blockReader);
if( m->in.pDoclist!=NULL ){
while( 1 ){
if( readerAtEnd(&m->in) ) return; /* nothing more to merge */
if( peekDocid(&m->in)>=iDocid ) break;
skipDocument(&m->in);
}
if( peekDocid(&m->in)>iDocid ){ /* [pIn] has no match with iDocid */
skipPositionList(&blockReader); /* skip this docid in the block */
continue;
}
readDocid(&m->in);
}
/* We have a document match. */
if( m->in.pDoclist==NULL || m->in.pDoclist->iType < DL_POSITIONS ){
/* We don't need to do a poslist merge. */
docListAddDocid(m->pOut, iDocid);
if( m->pOut->iType >= DL_POSITIONS ){
/* Copy all positions to the output doclist. */
while( 1 ){
int pos = readPosition(&blockReader);
if( pos==-1 ) break;
docListAddPos(m->pOut, pos);
}
docListAddEndPos(m->pOut);
} else skipPositionList(&blockReader);
continue;
}
mergePosList(m, iDocid, &blockReader);
}
}
static void mergeBlock(DocListMerge *m, DocList *pBlock){
DocListReader blockReader;
assert( pBlock->iType >= DL_POSITIONS );
readerInit(&blockReader, pBlock);
while( !readerAtEnd(&blockReader) ){
sqlite_int64 iDocid = readDocid(&blockReader);
if( m->in.pDoclist!=NULL ){
while( 1 ){
if( readerAtEnd(&m->in) ) return;
if( peekDocid(&m->in)>=iDocid ) break;
skipDocument(&m->in);
}
if( peekDocid(&m->in)>iDocid ){
skipPositionList(&blockReader);
continue;
}
readDocid(&m->in);
}
if( m->in.pDoclist==NULL || m->in.pDoclist->iType < DL_POSITIONS ){
docListAddDocid(m->pOut, iDocid);
if( m->pOut->iType >= DL_POSITIONS ){
while( 1 ){
int pos = readPosition(&blockReader);
if( pos==-1 ) break;
docListAddPos(m->pOut, pos);
}
docListAddEndPos(m->pOut);
} else skipPositionList(&blockReader);
continue;
}
mergePosList(m, iDocid, &blockReader);
}
}
