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.
index 54afa6f41760f7d481a8025b4862b450337097c6..bbe2fe4bce518c58212844ace32a20c5772f5ae2 100644 (file)
@@ -2205,7 +2205,8 @@ _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 (BTreeTupleIsPosting(pivot))
{
@@ -2250,6 +2251,10 @@ _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));