of AND and OR clauses. The key point here is that an OR on the
predicate side has to be treated gingerly: we may be able to prove
that the OR is implied even when no one of its components is implied.
For example (x OR y) implies (x OR y OR z) even though no one of x,
y, or z can be individually proven. This code handles both the
example shown recently by Sergey Koshcheyev and the one shown last
October by Dawid Kuroczko.
no held locks. This maintains the invariant that proclocks are present
only for procs that are holding or awaiting a lock; when this is not
true, LockRelease will fail. Per report from Stephen Clouse.
indexscans involving partial indexes. These would always be dominated
by a simple indexscan on such an index, so there's no point in considering
them. Fixes overoptimism in a patch I applied last October.
it was in 7.4, and add some comments explaining why it has to be this way.
I broke it for OR'd index predicates in a fit of code cleanup last summer.
Per example from Sergey Koshcheyev.
adjusting values:
> But to be on the safe side, it would make sense to do something similar
> to the BSD section, and comment about older distributions maybe needing
> to manipulate /proc/kernel/* directly.
Mark Kirkwood
in favor of looking at the flat file copy of pg_database during backend
startup. This should finally eliminate the various corner cases in which
backend startup fails unexpectedly because it isn't able to distinguish
live and dead tuples in pg_database. Simplify locking on pg_database
to be similar to the rules used with pg_shadow and pg_group, and eliminate
FlushRelationBuffers operations that were used only to reduce the odds
of failure of GetRawDatabaseInfo.
initdb forced due to addition of a trigger to pg_database.
! authentication. Use of this environment variable is not
! recommended for security reasons (some operating systems
! allow non-root users to see process environment variables via
! <application>ps</>); instead consider using the
! <filename>~/.pgpass</> file (see <xref linkend="libpq-pgpass">).
implement the md5() SQL-level function). The old code did the
following:
1. de-toast the datum
2. convert it to a cstring via textout()
3. get the length of the cstring via strlen()
Since we are treating the datum context as a blob of binary data,
the latter two steps are unnecessary. Once the data has been
detoasted, we can just use it as-is, and derive its length from
the varlena metadata.
This patch improves some run-of-the-mill md5() computations by
just under 10% in my limited tests, and passes the regression tests.
I also noticed that md5_text() wasn't checking the return value
of md5_hash(); encountering OOM at precisely the right moment
could result in returning a random md5 hash. This patch corrects
that. A better fix would be to make md5_hash() only return on
success (and/or allocate via palloc()), but since it's used in
the frontend as well I don't see an easy way to do that.
