From f84c8601d604811a530dadb53ddb52f08639e72b Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 23 May 2015 16:24:31 -0400 Subject: [PATCH] Add error check for lossy distance functions in index-only scans. Maybe we should actually support this, but for the moment let's just throw an error if the opclass tries it. --- src/backend/executor/nodeIndexonlyscan.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/src/backend/executor/nodeIndexonlyscan.c b/src/backend/executor/nodeIndexonlyscan.c index 61bd644ab7..976c77b76c 100644 --- a/src/backend/executor/nodeIndexonlyscan.c +++ b/src/backend/executor/nodeIndexonlyscan.c @@ -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 * level when the heap is not accessed, since tuple-level predicate