/* 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);
}
}
static void docListAddPosOffset(DocList *d, int iPos,
int iStartOffset, int iEndOffset){
assert( d->iType==DL_POSITIONS_OFFSETS );
docListAddPos(d, iPos);
appendVarint(d, iStartOffset-d->iLastOffset);
d->iLastOffset = iStartOffset;
appendVarint(d, iEndOffset-iStartOffset);
}
/* 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);
}
}
