/* 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);
}
}
/* Doclist multi-tool. Pass pUpdate==NULL to delete the indicated docid;
* otherwise pUpdate, which must contain only the single docid [iDocid], is
* inserted (if not present) or updated (if already present). */
static int docListUpdate(DocList *d, sqlite_int64 iDocid, DocList *pUpdate){
int modified = 0;
DocListReader reader;
char *p;
if( pUpdate!=NULL ){
assert( d->iType==pUpdate->iType);
assert( iDocid==firstDocid(pUpdate) );
}
readerInit(&reader, d);
while( !readerAtEnd(&reader) && peekDocid(&reader)<iDocid ){
skipDocument(&reader);
}
p = reader.p;
/* Delete if there is a matching element. */
if( !readerAtEnd(&reader) && iDocid==peekDocid(&reader) ){
skipDocument(&reader);
memmove(p, reader.p, docListEnd(d) - reader.p);
d->nData -= (reader.p - p);
modified = 1;
}
/* Insert if indicated. */
if( pUpdate!=NULL ){
int iDoclist = p-d->pData;
docListAddEndPos(pUpdate);
d->pData = realloc(d->pData, d->nData+pUpdate->nData);
p = d->pData + iDoclist;
memmove(p+pUpdate->nData, p, docListEnd(d) - p);
memcpy(p, pUpdate->pData, pUpdate->nData);
d->nData += pUpdate->nData;
modified = 1;
}
return modified;
}
/* 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);
}
}
