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Still more fixes for lossy-GiST-distance-functions patch.

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Fix confusion in documentation, substantial memory leakage if float8 or
float4 are pass-by-reference, and assorted comments that were obsoleted
by commit 98edd617f3.
This commit is contained in:
Tom Lane
2015-05-23 15:22:25 -04:00
parent 284bef2977
commit 821b821a24
5 changed files with 55 additions and 41 deletions
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29
src/backend/access/gist/gistget.c
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@ -191,20 +191,18 @@ gistindex_keytest(IndexScanDesc scan,
/*
* Call the Distance function to evaluate the distance. The
* arguments are the index datum (as a GISTENTRY*), the comparison
* datum, and the ordering operator's strategy number and subtype
* from pg_amop.
* datum, the ordering operator's strategy number and subtype from
* pg_amop, and the recheck flag.
*
* (Presently there's no need to pass the subtype since it'll
* always be zero, but might as well pass it for possible future
* use.)
*
* Distance functions get a recheck argument as well. In this
* case the returned distance is the lower bound of distance and
* needs to be rechecked. We return single recheck flag which
* means that both quals and distances are to be rechecked. We
* initialize the flag to 'false'. The flag was added in version
* 9.5 and the distance operators written before that won't know
* about the flag, and are never lossy.
* If the function sets the recheck flag, the returned distance is
* a lower bound on the true distance and needs to be rechecked.
* We initialize the flag to 'false'. This flag was added in
* version 9.5; distance functions written before that won't know
* about the flag, but are expected to never be lossy.
*/
recheck = false;
dist = FunctionCall5Coll(&key->sk_func,
@ -475,11 +473,22 @@ getNextNearest(IndexScanDesc scan)
{
if (so->orderByTypes[i] == FLOAT8OID)
{
#ifndef USE_FLOAT8_BYVAL
/* must free any old value to avoid memory leakage */
if (!scan->xs_orderbynulls[i])
pfree(DatumGetPointer(scan->xs_orderbyvals[i]));
#endif
scan->xs_orderbyvals[i] = Float8GetDatum(item->distances[i]);
scan->xs_orderbynulls[i] = false;
}
else if (so->orderByTypes[i] == FLOAT4OID)
{
/* convert distance function's result to ORDER BY type */
#ifndef USE_FLOAT4_BYVAL
/* must free any old value to avoid memory leakage */
if (!scan->xs_orderbynulls[i])
pfree(DatumGetPointer(scan->xs_orderbyvals[i]));
#endif
scan->xs_orderbyvals[i] = Float4GetDatum((float4) item->distances[i]);
scan->xs_orderbynulls[i] = false;
}
@ -491,7 +500,7 @@ getNextNearest(IndexScanDesc scan)
* calculated by the distance function to that. The
* executor won't actually need the order by values we
* return here, if there are no lossy results, so only
* insist on the datatype if the *recheck is set.
* insist on converting if the *recheck flag is set.
*/
if (scan->xs_recheckorderby)
elog(ERROR, "GiST operator family's FOR ORDER BY operator must return float8 or float4 if the distance function is lossy");