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Refactor fts2 loadSegmentLeaf() in preparation for prefix-searching.

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Prefix-searching will want to accumulate data across multiple leaves
in the segment, using LeavesReader instead of LeafReader is the first
step in that direction. (CVS 3881)

FossilOrigin-Name: 22ffdae4b6f3d0ea584dafa5268af7aa6fdcdc6e
This commit is contained in:
shess
2007-04-27 21:01:59 +00:00
parent 9310ef23e2
commit 1c7ebb0805
3 changed files with 50 additions and 31 deletions
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ext/fts2/fts2.c
+42 -23
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@@ -5079,45 +5079,64 @@ static int segmentMerge(fulltext_vtab *v, int iLevel){
return rc;
}
/* Read pData[nData] as a leaf node, and if the doclist for
** pTerm[nTerm] is present, merge it over *out (any duplicate doclists
** read from pData will overwrite those in *out).
/* Scan pReader for pTerm/nTerm, and merge the term's doclist over
** *out (any doclists with duplicate docids overwrite those in *out).
** Internal function for loadSegmentLeaf().
*/
static int loadSegmentLeaf(fulltext_vtab *v, const char *pData, int nData,
const char *pTerm, int nTerm, DataBuffer *out){
LeafReader reader;
assert( nData>1 );
assert( *pData=='\0' );
static int loadSegmentLeavesInt(fulltext_vtab *v, LeavesReader *pReader,
const char *pTerm, int nTerm, DataBuffer *out){
assert( nTerm>0 );
/* This code should never be called with buffered updates. */
assert( v->nPendingData<0 );
leafReaderInit(pData, nData, &reader);
while( !leafReaderAtEnd(&reader) ){
int c = leafReaderTermCmp(&reader, pTerm, nTerm);
/* Process while the prefix matches. */
while( !leavesReaderAtEnd(pReader) ){
/* TODO(shess) Really want leavesReaderTermCmp(), but that name is
** already taken to compare the terms of two LeavesReaders. Think
** on a better name. [Meanwhile, break encapsulation rather than
** use a confusing name.]
*/
int rc, c = leafReaderTermCmp(&pReader->leafReader, pTerm, nTerm);
if( c==0 ){
const char *pData = leavesReaderData(pReader);
int nData = leavesReaderDataBytes(pReader);
if( out->nData==0 ){
dataBufferReplace(out,
leafReaderData(&reader), leafReaderDataBytes(&reader));
dataBufferReplace(out, pData, nData);
}else{
DLReader readers[2];
DataBuffer result;
dlrInit(&readers[0], DL_DEFAULT, out->pData, out->nData);
dlrInit(&readers[1], DL_DEFAULT,
leafReaderData(&reader), leafReaderDataBytes(&reader));
dataBufferInit(&result, out->nData+leafReaderDataBytes(&reader));
dlrInit(&readers[1], DL_DEFAULT, pData, nData);
dataBufferInit(&result, out->nData+nData);
docListMerge(&result, readers, 2);
dataBufferDestroy(out);
*out = result;
dlrDestroy(&readers[0]);
dlrDestroy(&readers[1]);
}
}
if( c>=0 ) break;
leafReaderStep(&reader);
}
if( c>=0 ) break; /* Past any possible matches. */
rc = leavesReaderStep(v, pReader);
if( rc!=SQLITE_OK ) return rc;
}
leafReaderDestroy(&reader);
return SQLITE_OK;
}
/* Call loadSegmentLeavesInt() with pData/nData as input. */
static int loadSegmentLeaf(fulltext_vtab *v, const char *pData, int nData,
const char *pTerm, int nTerm, DataBuffer *out){
LeavesReader reader;
int rc;
assert( nData>1 );
assert( *pData=='\0' );
rc = leavesReaderInit(v, 0, 0, 0, pData, nData, &reader);
if( rc!=SQLITE_OK ) return rc;
rc = loadSegmentLeavesInt(v, &reader, pTerm, nTerm, out);
leavesReaderDestroy(&reader);
return rc;
}
/* Traverse the tree represented by pData[nData] looking for
** pTerm[nTerm], merging its doclist over *out if found (any duplicate
** doclists read from the segment rooted at pData will overwrite those