The results of the KNN-search test cases were indeterminate, as they asked
the system to sort pairs of points that are exactly equidistant from the
query reference point. It's a bit surprising that we've seen no
platform-specific failures from this in the buildfarm. Perhaps IEEE-float
math is well enough standardized that no such failures will ever occur on
supported platforms ... but since this entire regression test has yet to be
shipped in any non-alpha release, that seems like an unduly optimistic
assumption. Tweak the queries so that the correct output is uniquely
defined.
(The other queries in this test are also underdetermined; but it looks like
they are regurgitating index rows in insertion order, so for the moment
assume that that behavior is stable enough.)
Per Greg Stark's experiments with VAX. Back-patch to 9.5 where this test
script was introduced.
This reverts commit 5cdf25e168,
which was almost immediately proven insufficient by the buildfarm.
On second thought, the tables involved are not large enough that
autovacuum or autoanalyze would notice them; what seems far more
likely to be the culprit is the database-wide "vacuum analyze"
in the concurrent gist test. That thing has given us one headache
too many, so get rid of it in favor of targeted vacuuming of that
test's own tables only.
Paul Ramsey reported that commit 35fcb1b3d0
induced a core dump on commuted ORDER BY expressions, because it was
assuming that the indexorderby expression could be found verbatim in the
relevant equivalence class, but it wasn't there. We really don't need
anything that complicated anyway; for the data types likely to be used for
index ORDER BY operators in the foreseeable future, the exprType() of the
ORDER BY expression will serve fine. (The case where we'd have to work
harder is where the ORDER BY expression's result is only binary-compatible
with the declared input type of the ordering operator; long before worrying
about that, one would need to get rid of GiST's hard-wired assumption that
said datatype is float8.)
Aside from fixing that crash and adding a regression test for the case,
I did some desultory code review:
nodeIndexscan.c was likewise overthinking how hard it ought to work to
identify the datatype of the ORDER BY expressions.
Add comments explaining how come nodeIndexscan.c can get away with
simplifying assumptions about NULLS LAST ordering and no backward scan.
Revert no-longer-needed changes of find_ec_member_for_tle(); while the
new definition was no worse than the old, it wasn't better either, and
it might cause back-patching pain.
Revert entirely bogus additions to genam.h.
This adds a new GiST opclass method, 'fetch', which is used to reconstruct
the original Datum from the value stored in the index. Also, the 'canreturn'
index AM interface function gains a new 'attno' argument. That makes it
possible to use index-only scans on a multi-column index where some of the
opclasses support index-only scans but some do not.
This patch adds support in the box and point opclasses. Other opclasses
can added later as follow-on patches (btree_gist would be particularly
interesting).
Anastasia Lubennikova, with additional fixes and modifications by me.
That includes VACUUM on GIN, GiST and SP-GiST indexes, and B-tree indexes
large enough to cause page deletions in B-tree. Plus some other special
cases.
After this patch, the regression tests generate all different WAL record
types. Not all branches within the redo functions are covered, but it's a
step forward.
Tom Lane
Heikki Linnakangas