/*
* Detect whether a tsquery boolean expression requires any positive matches
* to values shown in the tsquery.
*
* This is needed to know whether a GIN index search requires full index scan.
* For example, 'x & !y' requires a match of x, so it's sufficient to scan
* entries for x; but 'x | !y' could match rows containing neither x nor y.
*/
bool
tsquery_requires_match(QueryItem *curitem)
{
/* since this function recurses, it could be driven to stack overflow */
check_stack_depth();
if (curitem->type == QI_VAL)
return true;
switch (curitem->qoperator.oper)
{
case OP_NOT:
/*
* Assume there are no required matches underneath a NOT. For
* some cases with nested NOTs, we could prove there's a required
* match, but it seems unlikely to be worth the trouble.
*/
return false;
case OP_AND:
/* If either side requires a match, we're good */
if (tsquery_requires_match(curitem + curitem->qoperator.left))
return true;
else
return tsquery_requires_match(curitem + 1);
case OP_OR:
/* Both sides must require a match */
if (tsquery_requires_match(curitem + curitem->qoperator.left))
return tsquery_requires_match(curitem + 1);
else
return false;
default:
elog(ERROR, "unrecognized operator: %d", curitem->qoperator.oper);
}
/* not reachable, but keep compiler quiet */
return false;
}
Datum
gin_extract_tsquery(PG_FUNCTION_ARGS)
{
TSQuery query = PG_GETARG_TSQUERY(0);
int32 *nentries = (int32 *) PG_GETARG_POINTER(1);
/* StrategyNumber strategy = PG_GETARG_UINT16(2); */
bool **ptr_partialmatch = (bool **) PG_GETARG_POINTER(3);
Pointer **extra_data = (Pointer **) PG_GETARG_POINTER(4);
/* bool **nullFlags = (bool **) PG_GETARG_POINTER(5); */
int32 *searchMode = (int32 *) PG_GETARG_POINTER(6);
Datum *entries = NULL;
*nentries = 0;
if (query->size > 0)
{
QueryItem *item = GETQUERY(query);
int32 i,
j;
bool *partialmatch;
int *map_item_operand;
/*
* If the query doesn't have any required positive matches (for
* instance, it's something like '! foo'), we have to do a full index
* scan.
*/
if (tsquery_requires_match(item))
*searchMode = GIN_SEARCH_MODE_DEFAULT;
else
*searchMode = GIN_SEARCH_MODE_ALL;
/* count number of VAL items */
j = 0;
for (i = 0; i < query->size; i++)
{
if (item[i].type == QI_VAL)
j++;
}
*nentries = j;
entries = (Datum *) palloc(sizeof(Datum) * j);
partialmatch = *ptr_partialmatch = (bool *) palloc(sizeof(bool) * j);
/*
* Make map to convert item's number to corresponding operand's (the
* same, entry's) number. Entry's number is used in check array in
* consistent method. We use the same map for each entry.
*/
*extra_data = (Pointer *) palloc(sizeof(Pointer) * j);
map_item_operand = (int *) palloc0(sizeof(int) * query->size);
/* Now rescan the VAL items and fill in the arrays */
j = 0;
for (i = 0; i < query->size; i++)
{
if (item[i].type == QI_VAL)
{
QueryOperand *val = &item[i].qoperand;
text *txt;
txt = cstring_to_text_with_len(GETOPERAND(query) + val->distance,
val->length);
entries[j] = PointerGetDatum(txt);
partialmatch[j] = val->prefix;
(*extra_data)[j] = (Pointer) map_item_operand;
map_item_operand[i] = j;
j++;
}
}
}
PG_FREE_IF_COPY(query, 0);
PG_RETURN_POINTER(entries);
}
