"Merlin Moncure" <[EMAIL PROTECTED]> writes:
> I took advantage of the holidays to update a production server (dual
> Opteron on win2k) from an 11/16 build (about beta5 or so) to the latest
> release candidate.  No configuration changes were made, just a binary
> swap and a server stop/start.  

> I was shocked to see that statement latency dropped by a fairly large
> margin.

Hmm ... I trawled through the CVS logs since 11/16, and did not see very
many changes that looked like they might improve performance (list
attached) --- and even of those, hardly any looked like the change would
be significant.  Do you know whether the query plans changed?  Are you
running few enough queries per connection that backend startup overhead
might be an issue?

                        regards, tom lane

2004-12-15 14:16  tgl

        * src/backend/access/nbtree/nbtutils.c: Calculation of
        keys_are_unique flag was wrong for cases involving redundant
        cross-datatype comparisons.  Per example from Merlin Moncure.

2004-12-02 10:32  momjian

        * configure, configure.in, doc/src/sgml/libpq.sgml,
        doc/src/sgml/ref/copy.sgml, src/interfaces/libpq/fe-connect.c,
        src/interfaces/libpq/fe-print.c, src/interfaces/libpq/fe-secure.c,
        src/interfaces/libpq/libpq-fe.h, src/interfaces/libpq/libpq-int.h:
        Rework libpq threaded SIGPIPE handling to avoid interference with
        calling applications.  This is done by blocking sigpipe in the
        libpq thread and using sigpending/sigwait to possibily discard any
        sigpipe we generated.

2004-12-01 20:34  tgl

        * src/: backend/optimizer/path/costsize.c,
        test/regress/expected/inherit.out, test/regress/expected/join.out,
        test/regress/sql/inherit.sql, test/regress/sql/join.sql: Make some
        adjustments to reduce platform dependencies in plan selection.  In
        particular, there was a mathematical tie between the two possible
        nestloop-with-materialized-inner-scan plans for a join (ie, we
        computed the same cost with either input on the inside), resulting
        in a roundoff error driven choice, if the relations were both small
        enough to fit in sort_mem.  Add a small cost factor to ensure we
        prefer materializing the smaller input.  This changes several
        regression test plans, but with any luck we will now have more
        stability across platforms.

2004-12-01 14:00  tgl

        * doc/src/sgml/catalogs.sgml, doc/src/sgml/diskusage.sgml,
        doc/src/sgml/perform.sgml, doc/src/sgml/release.sgml,
        src/backend/access/nbtree/nbtree.c, src/backend/catalog/heap.c,
        src/backend/catalog/index.c, src/backend/commands/vacuum.c,
        src/backend/optimizer/util/relnode.c, src/include/access/genam.h,
        src/include/nodes/relation.h, src/test/regress/expected/case.out,
        src/test/regress/expected/polymorphism.out: Change planner to use
        the current true disk file size as its estimate of a relation's
        number of blocks, rather than the possibly-obsolete value in
        pg_class.relpages.  Scale the value in pg_class.reltuples
        correspondingly to arrive at a hopefully more accurate number of
        rows.  When pg_class contains 0/0, estimate a tuple width from the
        column datatypes and divide that into current file size to estimate
        number of rows.  This improved methodology allows us to jettison
        the ancient hacks that put bogus default values into pg_class when
        a table is first created.  Also, per a suggestion from Simon, make
        VACUUM (but not VACUUM FULL or ANALYZE) adjust the value it puts
        into pg_class.reltuples to try to represent the mean tuple density
        instead of the minimal density that actually prevails just after
        VACUUM.  These changes alter the plans selected for certain
        regression tests, so update the expected files accordingly.  (I
        removed join_1.out because it's not clear if it still applies; we
        can add back any variant versions as they are shown to be needed.)

2004-11-21 17:57  tgl

        * src/backend/utils/hash/dynahash.c: Fix rounding problem in
        dynahash.c's decision about when the target fill factor has been
        exceeded.  We usually run with ffactor == 1, but the way the test
        was coded, it wouldn't split a bucket until the actual fill factor
        reached 2.0, because of use of integer division.  Change from > to
        >= so that it will split more aggressively when the table starts to
        get full.

2004-11-21 17:48  tgl

        * src/backend/utils/mmgr/portalmem.c: Reduce the default size of
        the PortalHashTable in order to save a few cycles during
        transaction exit.  A typical session probably wouldn't have as many
        as half a dozen portals open at once, so the original value of 64
        seems far larger than needed.

2004-11-20 15:19  tgl

        * src/backend/utils/cache/relcache.c: Avoid scanning the relcache
        during AtEOSubXact_RelationCache when there is nothing to do, which
        is most of the time.  This is another simple improvement to cut
        subtransaction entry/exit overhead.

2004-11-20 15:16  tgl

        * src/backend/storage/lmgr/lock.c: Reduce the default size of the
        local lock hash table.  There's usually no need for it to be nearly
        as big as the global hash table, and since it's not in shared
        memory it can grow if it does need to be bigger.  By reducing the
        size, we speed up hash_seq_search(), which saves a significant
        fraction of subtransaction entry/exit overhead.

2004-11-19 19:48  tgl

        * src/backend/tcop/postgres.c: Move pgstat_report_tabstat() call so
        that stats are not reported to the collector until the transaction
        commits.  Per recent discussion, this should avoid confusing
        autovacuum when an updating transaction runs for a long time.

2004-11-16 22:13  neilc

        * src/backend/access/: hash/hash.c, nbtree/nbtree.c:
        Micro-optimization of markpos() and restrpos() in btree and hash
        indexes.  Rather than using ReadBuffer() to increment the reference
        count on an already-pinned buffer, we should use
        IncrBufferRefCount() as it is faster and does not require acquiring
        the BufMgrLock.

2004-11-16 19:14  tgl

        * src/: backend/main/main.c, backend/port/win32/signal.c,
        backend/postmaster/pgstat.c, backend/postmaster/postmaster.c,
        include/port/win32.h: Fix Win32 problems with signals and sockets,
        by making the forkexec code even uglier than it was already :-(. 
        Also, on Windows only, use temporary shared memory segments instead
        of ordinary files to pass over critical variable values from
        postmaster to child processes.  Magnus Hagander

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