From 97cda93d81dc89ab05703e1c3344525ab268e49f Mon Sep 17 00:00:00 2001 From: Peter Geoghegan Date: Mon, 30 Mar 2020 12:03:57 -0700 Subject: [PATCH] Consistently truncate non-key suffix columns. INCLUDE indexes failed to have their non-key attributes physically truncated away in certain rare cases. This led to physically larger pivot tuples that contained useless non-key attribute values. The impact on users should be negligible, but this is still clearly a regression (Postgres 11 supports INCLUDE indexes, and yet was not affected). The bug appeared in commit dd299df8, which introduced "true" suffix truncation of key attributes. Discussion: https://postgr.es/m/CAH2-Wz=E8pkV9ivRSFHtv812H5ckf8s1-yhx61_WrJbKccGcrQ@mail.gmail.com Backpatch: 12-, where "true" suffix truncation was introduced. --- src/backend/access/nbtree/nbtutils.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c index 93fab264ae..a1e7636adb 100644 --- a/src/backend/access/nbtree/nbtutils.c +++ b/src/backend/access/nbtree/nbtutils.c @@ -2143,7 +2143,8 @@ _bt_truncate(Relation rel, IndexTuple lastleft, IndexTuple firstright, { IndexTuple tidpivot; - pivot = index_truncate_tuple(itupdesc, firstright, keepnatts); + pivot = index_truncate_tuple(itupdesc, firstright, + Min(keepnatts, nkeyatts)); /* * If there is a distinguishing key attribute within new pivot tuple, @@ -2173,6 +2174,10 @@ _bt_truncate(Relation rel, IndexTuple lastleft, IndexTuple firstright, /* * No truncation was possible, since key attributes are all equal. * It's necessary to add a heap TID attribute to the new pivot tuple. + * + * This path is only taken when rel is not an INCLUDE index. It + * avoids a second palloc0() by avoiding the index_truncate_tuple() + * call completely. */ Assert(natts == nkeyatts); newsize = IndexTupleSize(firstright) + MAXALIGN(sizeof(ItemPointerData));