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Add error check for lossy distance functions in index-only scans.

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Maybe we should actually support this, but for the moment let's just
throw an error if the opclass tries it.
This commit is contained in:
Tom Lane 2015-05-23 16:24:31 -04:00
parent 72809480d6
commit f84c8601d6
1 changed files with 13 additions and 0 deletions
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13
src/backend/executor/nodeIndexonlyscan.c
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@ -165,6 +165,19 @@ IndexOnlyNext(IndexOnlyScanState *node)
} }
} }
/*
* We don't currently support rechecking ORDER BY distances. (In
* principle, if the index can support retrieval of the originally
* indexed value, it should be able to produce an exact distance
* calculation too. So it's not clear that adding code here for
* recheck/re-sort would be worth the trouble. But we should at least
* throw an error if someone tries it.)
*/
if (scandesc->numberOfOrderBys > 0 && scandesc->xs_recheckorderby)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("lossy distance functions are not supported in index-only scans")));
/* /*
* Predicate locks for index-only scans must be acquired at the page * Predicate locks for index-only scans must be acquired at the page
* level when the heap is not accessed, since tuple-level predicate * level when the heap is not accessed, since tuple-level predicate