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Teach SP-GiST to do index-only scans.

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Operator classes can specify whether or not they support this; this
preserves the flexibility to use lossy representations within an index.

In passing, move constant data about a given index into the rd_amcache
cache area, instead of doing fresh lookups each time we start an index
operation.  This is mainly to try to make sure that spgcanreturn() has
insignificant cost; I still don't have any proof that it matters for
actual index accesses.  Also, get rid of useless copying of FmgrInfo
pointers; we can perfectly well use the relcache's versions in-place.
This commit is contained in:
Tom Lane
2011-12-19 14:58:41 -05:00
parent 3695a55513
commit 9220362493
10 changed files with 286 additions and 172 deletions
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13
src/backend/access/spgist/spgtextproc.c
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@ -51,6 +51,7 @@ spg_text_config(PG_FUNCTION_ARGS)
cfg->prefixType = TEXTOID;
cfg->labelType = CHAROID;
cfg->canReturnData = true;
cfg->longValuesOK = true; /* suffixing will shorten long values */
PG_RETURN_VOID();
}
@ -521,7 +522,10 @@ spg_text_leaf_consistent(PG_FUNCTION_ARGS)
queryLen = VARSIZE_ANY_EXHDR(query);
/* For equality, we needn't reconstruct fullValue if not same length */
/*
* For an equality check, we needn't reconstruct fullValue if not same
* length; it can't match
*/
if (strategy == BTEqualStrategyNumber && queryLen != fullLen)
PG_RETURN_BOOL(false);
@ -529,15 +533,20 @@ spg_text_leaf_consistent(PG_FUNCTION_ARGS)
if (VARSIZE_ANY_EXHDR(leafValue) == 0 && level > 0)
{
fullValue = VARDATA(reconstrValue);
out->leafValue = PointerGetDatum(reconstrValue);
}
else
{
fullValue = palloc(fullLen);
text *fullText = palloc(VARHDRSZ + fullLen);
SET_VARSIZE(fullText, VARHDRSZ + fullLen);
fullValue = VARDATA(fullText);
if (level)
memcpy(fullValue, VARDATA(reconstrValue), level);
if (VARSIZE_ANY_EXHDR(leafValue) > 0)
memcpy(fullValue + level, VARDATA_ANY(leafValue),
VARSIZE_ANY_EXHDR(leafValue));
out->leafValue = PointerGetDatum(fullText);
}
/* Run the appropriate type of comparison */