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1516 lines
61 KiB
Plaintext
From owner-pgsql-hackers@hub.org Sun Jun 14 18:45:04 1998
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Received: from hub.org (hub.org [209.47.148.200])
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id AA07922; Sun, 14 Jun 1998 15:35:13 -0700
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From: dg@illustra.com (David Gould)
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Message-Id: <9806142235.AA07922@hawk.illustra.com>
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Subject: [HACKERS] performance tests, initial results
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To: pgsql-hackers@postgreSQL.org
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Date: Sun, 14 Jun 1998 15:35:13 -0700 (PDT)
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Mime-Version: 1.0
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Content-Type: text/plain; charset=US-ASCII
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Content-Transfer-Encoding: 7bit
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Sender: owner-pgsql-hackers@hub.org
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Precedence: bulk
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Status: RO
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I have been playing a little with the performance tests found in
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pgsql/src/tests/performance and have a few observations that might be of
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minor interest.
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The tests themselves are simple enough although the result parsing in the
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driver did not work on Linux. I am enclosing a patch below to fix this. I
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think it will also work better on the other systems.
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A summary of results from my testing are below. Details are at the bottom
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of this message.
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My test system is 'leslie':
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linux 2.0.32, gcc version 2.7.2.3
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P133, HX chipset, 512K L2, 32MB mem
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NCR810 fast scsi, Quantum Atlas 2GB drive (7200 rpm).
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Results Summary (times in seconds)
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Single txn 8K txn Create 8K idx 8K random Simple
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Case Description 8K insert 8K insert Index Insert Scans Orderby
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=================== ========== ========= ====== ====== ========= =======
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1 From Distribution
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P90 FreeBsd -B256 39.56 1190.98 3.69 46.65 65.49 2.27
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IDE
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2 Running on leslie
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P133 Linux 2.0.32 15.48 326.75 2.99 20.69 35.81 1.68
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SCSI 32M
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3 leslie, -o -F
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no forced writes 15.90 24.98 2.63 20.46 36.43 1.69
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4 leslie, -o -F
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no ASSERTS 14.92 23.23 1.38 18.67 33.79 1.58
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5 leslie, -o -F -B2048
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more buffers 21.31 42.28 2.65 25.74 42.26 1.72
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6 leslie, -o -F -B2048
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more bufs, no ASSERT 20.52 39.79 1.40 24.77 39.51 1.55
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Case to Case Difference Factors (+ is faster)
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Single txn 8K txn Create 8K idx 8K random Simple
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Case Description 8K insert 8K insert Index Insert Scans Orderby
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=================== ========== ========= ====== ====== ========= =======
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leslie vs BSD P90. 2.56 3.65 1.23 2.25 1.83 1.35
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(noflush -F) vs no -F -1.03 13.08 1.14 1.01 -1.02 1.00
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No Assert vs Assert 1.05 1.07 1.90 1.06 1.07 1.09
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-B256 vs -B2048 1.34 1.69 1.01 1.26 1.16 1.02
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Observations:
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- leslie (P133 linux) appears to be about 1.8 times faster than the
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P90 BSD system used for the test result distributed with the source, not
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counting the 8K txn insert case which was completely disk bound.
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- SCSI disks make a big (factor of 3.6) difference. During this test the
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disk was hammering and cpu utilization was < 10%.
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- Assertion checking seems to cost about 7% except for create index where
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it costs 90%
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- the -F option to avoid flushing buffers has tremendous effect if there are
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many very small transactions. Or, another way, flushing at the end of the
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transaction is a major disaster for performance.
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- Something is very wrong with our buffer cache implementation. Going from
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256 buffers to 2048 buffers costs an average of 25%. In the 8K txn case
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it costs about 70%. I see looking at the code and profiling that in the 8K
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txn case this is in BufferSync() which examines all the buffers at commit
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time. I don't quite understand why it is so costly for the single 8K row
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txn (35%) though.
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It would be nice to have some more tests. Maybe the Wisconsin stuff will
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be useful.
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----------------- patch to test harness. apply from pgsql ------------
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*** src/test/performance/runtests.pl.orig Sun Jun 14 11:34:04 1998
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Differences %
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----------------- patch to test harness. apply from pgsql ------------
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*** src/test/performance/runtests.pl.orig Sun Jun 14 11:34:04 1998
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--- src/test/performance/runtests.pl Sun Jun 14 12:07:30 1998
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***************
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*** 84,123 ****
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open (STDERR, ">$TmpFile") or die;
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select (STDERR); $| = 1;
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! for ($i = 0; $i <= $#perftests; $i++)
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! {
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$test = $perftests[$i];
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($test, $XACTBLOCK) = split (/ /, $test);
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$runtest = $test;
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! if ( $test =~ /\.ntm/ )
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! {
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! #
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# No timing for this queries
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- #
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close (STDERR); # close $TmpFile
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open (STDERR, ">/dev/null") or die;
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$runtest =~ s/\.ntm//;
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}
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! else
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! {
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close (STDOUT);
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open(STDOUT, ">&SAVEOUT");
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print STDOUT "\nRunning: $perftests[$i+1] ...";
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close (STDOUT);
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open (STDOUT, ">/dev/null") or die;
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select (STDERR); $| = 1;
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! printf "$perftests[$i+1]: ";
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}
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do "sqls/$runtest";
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# Restore STDERR to $TmpFile
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! if ( $test =~ /\.ntm/ )
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! {
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close (STDERR);
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open (STDERR, ">>$TmpFile") or die;
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}
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-
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select (STDERR); $| = 1;
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$i++;
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}
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--- 84,116 ----
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open (STDERR, ">$TmpFile") or die;
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select (STDERR); $| = 1;
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! for ($i = 0; $i <= $#perftests; $i++) {
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$test = $perftests[$i];
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($test, $XACTBLOCK) = split (/ /, $test);
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$runtest = $test;
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! if ( $test =~ /\.ntm/ ) {
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# No timing for this queries
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close (STDERR); # close $TmpFile
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open (STDERR, ">/dev/null") or die;
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$runtest =~ s/\.ntm//;
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}
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! else {
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close (STDOUT);
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open(STDOUT, ">&SAVEOUT");
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print STDOUT "\nRunning: $perftests[$i+1] ...";
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close (STDOUT);
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open (STDOUT, ">/dev/null") or die;
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select (STDERR); $| = 1;
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! print "$perftests[$i+1]: ";
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}
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do "sqls/$runtest";
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# Restore STDERR to $TmpFile
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! if ( $test =~ /\.ntm/ ) {
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close (STDERR);
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open (STDERR, ">>$TmpFile") or die;
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}
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select (STDERR); $| = 1;
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$i++;
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}
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***************
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*** 128,138 ****
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open (TMPF, "<$TmpFile") or die;
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open (RESF, ">$ResFile") or die;
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! while (<TMPF>)
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! {
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! $str = $_;
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! ($test, $rtime) = split (/:/, $str);
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! ($tmp, $rtime, $rest) = split (/[ ]+/, $rtime);
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! print RESF "$test: $rtime\n";
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}
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--- 121,130 ----
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open (TMPF, "<$TmpFile") or die;
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open (RESF, ">$ResFile") or die;
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! while (<TMPF>) {
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! if (m/^(.*: ).* ([0-9:.]+) *elapsed/) {
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! ($test, $rtime) = ($1, $2);
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! print RESF $test, $rtime, "\n";
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! }
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}
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------------------------------------------------------------------------
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------------------------- testcase detail --------------------------
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1. from distribution
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DBMS: PostgreSQL 6.2b10
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OS: FreeBSD 2.1.5-RELEASE
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HardWare: i586/90, 24M RAM, IDE
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StartUp: postmaster -B 256 '-o -S 2048' -S
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Compiler: gcc 2.6.3
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Compiled: -O, without CASSERT checking, with
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-DTBL_FREE_CMD_MEMORY (to free memory
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if BEGIN/END after each query execution)
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DB connection startup: 0.20
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8192 INSERTs INTO SIMPLE (1 xact): 39.58
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8192 INSERTs INTO SIMPLE (8192 xacts): 1190.98
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Create INDEX on SIMPLE: 3.69
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8192 INSERTs INTO SIMPLE with INDEX (1 xact): 46.65
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8192 random INDEX scans on SIMPLE (1 xact): 65.49
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ORDER BY SIMPLE: 2.27
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2. run on leslie with asserts
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DBMS: PostgreSQL 6.3.2 (plus changes to 98/06/01)
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OS: Linux 2.0.32 leslie
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HardWare: i586/133 HX 512, 32M RAM, fast SCSI, 7200rpm
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StartUp: postmaster -B 256 '-o -S 2048' -S
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Compiler: gcc 2.7.2.3
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Compiled: -O, WITH CASSERT checking, with
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-DTBL_FREE_CMD_MEMORY (to free memory
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if BEGIN/END after each query execution)
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DB connection startup: 0.10
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8192 INSERTs INTO SIMPLE (1 xact): 15.48
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8192 INSERTs INTO SIMPLE (8192 xacts): 326.75
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Create INDEX on SIMPLE: 2.99
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8192 INSERTs INTO SIMPLE with INDEX (1 xact): 20.69
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8192 random INDEX scans on SIMPLE (1 xact): 35.81
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ORDER BY SIMPLE: 1.68
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3. with -F to avoid forced i/o
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DBMS: PostgreSQL 6.3.2 (plus changes to 98/06/01)
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OS: Linux 2.0.32 leslie
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HardWare: i586/133 HX 512, 32M RAM, fast SCSI, 7200rpm
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StartUp: postmaster -B 256 '-o -S 2048 -F' -S
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Compiler: gcc 2.7.2.3
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Compiled: -O, WITH CASSERT checking, with
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-DTBL_FREE_CMD_MEMORY (to free memory
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if BEGIN/END after each query execution)
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DB connection startup: 0.10
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8192 INSERTs INTO SIMPLE (1 xact): 15.90
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8192 INSERTs INTO SIMPLE (8192 xacts): 24.98
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Create INDEX on SIMPLE: 2.63
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8192 INSERTs INTO SIMPLE with INDEX (1 xact): 20.46
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8192 random INDEX scans on SIMPLE (1 xact): 36.43
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ORDER BY SIMPLE: 1.69
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4. no asserts, -F to avoid forced I/O
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DBMS: PostgreSQL 6.3.2 (plus changes to 98/06/01)
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OS: Linux 2.0.32 leslie
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HardWare: i586/133 HX 512, 32M RAM, fast SCSI, 7200rpm
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StartUp: postmaster -B 256 '-o -S 2048' -S
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Compiler: gcc 2.7.2.3
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Compiled: -O, No CASSERT checking, with
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-DTBL_FREE_CMD_MEMORY (to free memory
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if BEGIN/END after each query execution)
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DB connection startup: 0.10
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8192 INSERTs INTO SIMPLE (1 xact): 14.92
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8192 INSERTs INTO SIMPLE (8192 xacts): 23.23
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Create INDEX on SIMPLE: 1.38
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8192 INSERTs INTO SIMPLE with INDEX (1 xact): 18.67
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8192 random INDEX scans on SIMPLE (1 xact): 33.79
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ORDER BY SIMPLE: 1.58
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5. with more buffers (2048 vs 256) and -F to avoid forced i/o
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DBMS: PostgreSQL 6.3.2 (plus changes to 98/06/01)
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OS: Linux 2.0.32 leslie
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HardWare: i586/133 HX 512, 32M RAM, fast SCSI, 7200rpm
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StartUp: postmaster -B 2048 '-o -S 2048 -F' -S
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Compiler: gcc 2.7.2.3
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Compiled: -O, WITH CASSERT checking, with
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-DTBL_FREE_CMD_MEMORY (to free memory
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if BEGIN/END after each query execution)
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DB connection startup: 0.11
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8192 INSERTs INTO SIMPLE (1 xact): 21.31
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8192 INSERTs INTO SIMPLE (8192 xacts): 42.28
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Create INDEX on SIMPLE: 2.65
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8192 INSERTs INTO SIMPLE with INDEX (1 xact): 25.74
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8192 random INDEX scans on SIMPLE (1 xact): 42.26
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ORDER BY SIMPLE: 1.72
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6. No Asserts, more buffers (2048 vs 256) and -F to avoid forced i/o
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DBMS: PostgreSQL 6.3.2 (plus changes to 98/06/01)
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OS: Linux 2.0.32 leslie
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HardWare: i586/133 HX 512, 32M RAM, fast SCSI, 7200rpm
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StartUp: postmaster -B 2048 '-o -S 2048 -F' -S
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Compiler: gcc 2.7.2.3
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Compiled: -O, No CASSERT checking, with
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-DTBL_FREE_CMD_MEMORY (to free memory
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if BEGIN/END after each query execution)
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DB connection startup: 0.11
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8192 INSERTs INTO SIMPLE (1 xact): 20.52
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8192 INSERTs INTO SIMPLE (8192 xacts): 39.79
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Create INDEX on SIMPLE: 1.40
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8192 INSERTs INTO SIMPLE with INDEX (1 xact): 24.77
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8192 random INDEX scans on SIMPLE (1 xact): 39.51
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ORDER BY SIMPLE: 1.55
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---------------------------------------------------------------------
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-dg
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David Gould dg@illustra.com 510.628.3783 or 510.305.9468
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Informix Software (No, really) 300 Lakeside Drive Oakland, CA 94612
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"Don't worry about people stealing your ideas. If your ideas are any
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good, you'll have to ram them down people's throats." -- Howard Aiken
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From owner-pgsql-hackers@hub.org Tue Oct 19 10:31:10 1999
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Received: from renoir.op.net (root@renoir.op.net [209.152.193.4])
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for <maillist@candle.pha.pa.us>; Tue, 19 Oct 1999 10:31:08 -0400 (EDT)
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Tue, 19 Oct 1999 10:09:15 -0400 (EDT)
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To: "Hiroshi Inoue" <Inoue@tpf.co.jp>
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cc: "Vadim Mikheev" <vadim@krs.ru>, pgsql-hackers@postgreSQL.org
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Subject: Re: [HACKERS] mdnblocks is an amazing time sink in huge relations
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In-reply-to: Your message of Tue, 19 Oct 1999 19:03:22 +0900
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<000801bf1a19$2d88ae20$2801007e@cadzone.tpf.co.jp>
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Date: Tue, 19 Oct 1999 10:09:15 -0400
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Message-ID: <9036.940342155@sss.pgh.pa.us>
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From: Tom Lane <tgl@sss.pgh.pa.us>
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Sender: owner-pgsql-hackers@postgreSQL.org
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Status: RO
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"Hiroshi Inoue" <Inoue@tpf.co.jp> writes:
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> 1. shared cache holds committed system tuples.
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> 2. private cache holds uncommitted system tuples.
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> 3. relpages of shared cache are updated immediately by
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> phisical change and corresponding buffer pages are
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> marked dirty.
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> 4. on commit, the contents of uncommitted tuples except
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> relpages,reltuples,... are copied to correponding tuples
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> in shared cache and the combined contents are
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> committed.
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> If so,catalog cache invalidation would be no longer needed.
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> But synchronization of the step 4. may be difficult.
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I think the main problem is that relpages and reltuples shouldn't
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be kept in pg_class columns at all, because they need to have
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very different update behavior from the other pg_class columns.
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The rest of pg_class is update-on-commit, and we can lock down any one
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row in the normal MVCC way (if transaction A has modified a row and
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transaction B also wants to modify it, B waits for A to commit or abort,
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so it can know which version of the row to start from). Furthermore,
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there can legitimately be several different values of a row in use in
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different places: the latest committed, an uncommitted modification, and
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one or more old values that are still being used by active transactions
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because they were current when those transactions started. (BTW, the
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present relcache is pretty bad about maintaining pure MVCC transaction
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semantics like this, but it seems clear to me that that's the direction
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we want to go in.)
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relpages cannot operate this way. To be useful for avoiding lseeks,
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relpages *must* change exactly when the physical file changes. It
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matters not at all whether the particular transaction that extended the
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file ultimately commits or not. Moreover there can be only one correct
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value (per relation) across the whole system, because there is only one
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length of the relation file.
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If we want to take reltuples seriously and try to maintain it
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on-the-fly, then I think it needs still a third behavior. Clearly
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it cannot be updated using MVCC rules, or we lose all writer
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concurrency (if A has added tuples to a rel, B would have to wait
|
|
for A to commit before it could update reltuples...). Furthermore
|
|
"updating" isn't a simple matter of storing what you think the new
|
|
value is; otherwise two transactions adding tuples in parallel would
|
|
leave the wrong answer after B commits and overwrites A's value.
|
|
I think it would work for each transaction to keep track of a net delta
|
|
in reltuples for each table it's changed (total tuples added less total
|
|
tuples deleted), and then atomically add that value to the table's
|
|
shared reltuples counter during commit. But that still leaves the
|
|
problem of how you use the counter during a transaction to get an
|
|
accurate answer to the question "If I scan this table now, how many tuples
|
|
will I see?" At the time the question is asked, the current shared
|
|
counter value might include the effects of transactions that have
|
|
committed since your transaction started, and therefore are not visible
|
|
under MVCC rules. I think getting the correct answer would involve
|
|
making an instantaneous copy of the current counter at the start of
|
|
your xact, and then adding your own private net-uncommitted-delta to
|
|
the saved shared counter value when asked the question. This doesn't
|
|
look real practical --- you'd have to save the reltuples counts of
|
|
*all* tables in the database at the start of each xact, on the off
|
|
chance that you might need them. Ugh. Perhaps someone has a better
|
|
idea. In any case, reltuples clearly needs different mechanisms than
|
|
the ordinary fields in pg_class do, because updating it will be a
|
|
performance bottleneck otherwise.
|
|
|
|
If we allow reltuples to be updated only by vacuum-like events, as
|
|
it is now, then I think keeping it in pg_class is still OK.
|
|
|
|
In short, it seems clear to me that relpages should be removed from
|
|
pg_class and kept somewhere else if we want to make it more reliable
|
|
than it is now, and the same for reltuples (but reltuples doesn't
|
|
behave the same as relpages, and probably ought to be handled
|
|
differently).
|
|
|
|
regards, tom lane
|
|
|
|
************
|
|
|
|
From owner-pgsql-hackers@hub.org Tue Oct 19 21:25:30 1999
|
|
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id KAA01715; Wed, 20 Oct 1999 10:05:14 +0900
|
|
From: "Hiroshi Inoue" <Inoue@tpf.co.jp>
|
|
To: "Tom Lane" <tgl@sss.pgh.pa.us>
|
|
Cc: <pgsql-hackers@postgreSQL.org>
|
|
Subject: RE: [HACKERS] mdnblocks is an amazing time sink in huge relations
|
|
Date: Wed, 20 Oct 1999 10:09:13 +0900
|
|
Message-ID: <000501bf1a97$b925a860$2801007e@cadzone.tpf.co.jp>
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MIME-Version: 1.0
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Sender: owner-pgsql-hackers@postgreSQL.org
|
|
Status: RO
|
|
|
|
> -----Original Message-----
|
|
> From: Hiroshi Inoue [mailto:Inoue@tpf.co.jp]
|
|
> Sent: Tuesday, October 19, 1999 6:45 PM
|
|
> To: Tom Lane
|
|
> Cc: pgsql-hackers@postgreSQL.org
|
|
> Subject: RE: [HACKERS] mdnblocks is an amazing time sink in huge
|
|
> relations
|
|
>
|
|
>
|
|
> >
|
|
> > "Hiroshi Inoue" <Inoue@tpf.co.jp> writes:
|
|
>
|
|
> [snip]
|
|
>
|
|
> >
|
|
> > > Deletion is necessary only not to consume disk space.
|
|
> > >
|
|
> > > For example vacuum could remove not deleted files.
|
|
> >
|
|
> > Hmm ... interesting idea ... but I can hear the complaints
|
|
> > from users already...
|
|
> >
|
|
>
|
|
> My idea is only an analogy of PostgreSQL's simple recovery
|
|
> mechanism of tuples.
|
|
>
|
|
> And my main point is
|
|
> "delete fails after commit" doesn't harm the database
|
|
> except that not deleted files consume disk space.
|
|
>
|
|
> Of cource,it's preferable to delete relation files immediately
|
|
> after(or just when) commit.
|
|
> Useless files are visible though useless tuples are invisible.
|
|
>
|
|
|
|
Anyway I don't need "DROP TABLE inside transactions" now
|
|
and my idea is originally for that issue.
|
|
|
|
After a thought,I propose the following solution.
|
|
|
|
1. mdcreate() couldn't create existent relation files.
|
|
If the existent file is of length zero,we would overwrite
|
|
the file.(seems the comment in md.c says so but the
|
|
code doesn't do so).
|
|
If the file is an Index relation file,we would overwrite
|
|
the file.
|
|
|
|
2. mdunlink() couldn't unlink non-existent relation files.
|
|
mdunlink() doesn't call elog(ERROR) even if the file
|
|
doesn't exist,though I couldn't find where to change
|
|
now.
|
|
mdopen() doesn't call elog(ERROR) even if the file
|
|
doesn't exist and leaves the relation as CLOSED.
|
|
|
|
Comments ?
|
|
|
|
Regards.
|
|
|
|
Hiroshi Inoue
|
|
Inoue@tpf.co.jp
|
|
|
|
************
|
|
|
|
From pgsql-hackers-owner+M6267@hub.org Sun Aug 27 21:46:37 2000
|
|
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for <pgsql-hackers@postgreSQL.org>; Sun, 27 Aug 2000 20:05:29 -0400 (EDT)
|
|
To: pgsql-hackers@postgreSQL.org
|
|
Subject: [HACKERS] Possible performance improvement: buffer replacement policy
|
|
Date: Sun, 27 Aug 2000 20:05:29 -0400
|
|
Message-ID: <1601.967421129@sss.pgh.pa.us>
|
|
From: Tom Lane <tgl@sss.pgh.pa.us>
|
|
X-Mailing-List: pgsql-hackers@postgresql.org
|
|
Precedence: bulk
|
|
Sender: pgsql-hackers-owner@hub.org
|
|
Status: RO
|
|
|
|
Those of you with long memories may recall a benchmark that Edmund Mergl
|
|
drew our attention to back in May '99. That test showed extremely slow
|
|
performance for updating a table with many indexes (about 20). At the
|
|
time, it seemed the problem was due to bad performance of btree with
|
|
many equal keys, so I thought I'd go back and retry the benchmark after
|
|
this latest round of btree hackery.
|
|
|
|
The good news is that btree itself seems to be pretty well fixed; the
|
|
bad news is that the benchmark is still slow for large numbers of rows.
|
|
The problem is I/O: the CPU mostly sits idle waiting for the disk.
|
|
As best I can tell, the difficulty is that the working set of pages
|
|
needed to update this many indexes is too large compared to the number
|
|
of disk buffers Postgres is using. (I was running with -B 1000 and
|
|
looking at behavior for a 100000-row test table. This gave me a table
|
|
size of 3876 pages, plus 11526 pages in 20 indexes.)
|
|
|
|
Of course, there's only so much we can do when the number of buffers
|
|
is too small, but I still started to wonder if we are using the buffers
|
|
as effectively as we can. Some tracing showed that most of the pages
|
|
of the indexes were being read and written multiple times within a
|
|
single UPDATE query, while most of the pages of the table proper were
|
|
fetched and written only once. That says we're not using the buffers
|
|
as well as we could; the index pages are not being kept in memory when
|
|
they should be. In a query like this, we should displace main-table
|
|
pages sooner to allow keeping more index pages in cache --- but with
|
|
the simple LRU replacement method we use, once a page has been loaded
|
|
it will stay in cache for at least the next NBuffers (-B) page
|
|
references, no matter what. With a large NBuffers that's a long time.
|
|
|
|
I've come across an interesting article:
|
|
The LRU-K Page Replacement Algorithm For Database Disk Buffering
|
|
Elizabeth J. O'Neil, Patrick E. O'Neil, Gerhard Weikum
|
|
Proceedings of the 1993 ACM SIGMOD international conference
|
|
on Management of Data, May 1993
|
|
(If you subscribe to the ACM digital library, you can get a PDF of this
|
|
from there.) This article argues that standard LRU buffer management is
|
|
inherently not great for database caches, and that it's much better to
|
|
replace pages on the basis of time since the K'th most recent reference,
|
|
not just time since the most recent one. K=2 is enough to get most of
|
|
the benefit. The big win is that you are measuring an actual page
|
|
interreference time (between the last two references) and not just
|
|
dealing with a lower-bound guess on the interreference time. Frequently
|
|
used pages are thus much more likely to stay in cache.
|
|
|
|
It looks like it wouldn't take too much work to replace shared buffers
|
|
on the basis of LRU-2 instead of LRU, so I'm thinking about trying it.
|
|
|
|
Has anyone looked into this area? Is there a better method to try?
|
|
|
|
regards, tom lane
|
|
|
|
From prlw1@newn.cam.ac.uk Fri Jan 19 12:54:45 2001
|
|
Received: from henry.newn.cam.ac.uk (henry.newn.cam.ac.uk [131.111.204.130])
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|
for <pgman@candle.pha.pa.us>; Fri, 19 Jan 2001 12:54:44 -0500 (EST)
|
|
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|
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id 14Jfj6-0001cq-00; Fri, 19 Jan 2001 17:53:28 +0000
|
|
Date: Fri, 19 Jan 2001 17:53:28 +0000
|
|
From: Patrick Welche <prlw1@newn.cam.ac.uk>
|
|
To: Bruce Momjian <pgman@candle.pha.pa.us>
|
|
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@postgreSQL.org
|
|
Subject: Re: [HACKERS] Possible performance improvement: buffer replacement policy
|
|
Message-ID: <20010119175328.A6223@quartz.newn.cam.ac.uk>
|
|
Reply-To: prlw1@cam.ac.uk
|
|
References: <1601.967421129@sss.pgh.pa.us> <200101191703.MAA25873@candle.pha.pa.us>
|
|
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|
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|
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|
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|
|
In-Reply-To: <200101191703.MAA25873@candle.pha.pa.us>; from pgman@candle.pha.pa.us on Fri, Jan 19, 2001 at 12:03:58PM -0500
|
|
Status: RO
|
|
|
|
On Fri, Jan 19, 2001 at 12:03:58PM -0500, Bruce Momjian wrote:
|
|
>
|
|
> Tom, did we ever test this? I think we did and found that it was the
|
|
> same or worse, right?
|
|
|
|
(Funnily enough, I just read that message:)
|
|
|
|
To: Bruce Momjian <pgman@candle.pha.pa.us>
|
|
cc: pgsql-hackers@postgreSQL.org
|
|
Subject: Re: [HACKERS] Possible performance improvement: buffer replacement policy
|
|
In-reply-to: <200010161541.LAA06653@candle.pha.pa.us>
|
|
References: <200010161541.LAA06653@candle.pha.pa.us>
|
|
Comments: In-reply-to Bruce Momjian <pgman@candle.pha.pa.us>
|
|
message dated "Mon, 16 Oct 2000 11:41:41 -0400"
|
|
Date: Mon, 16 Oct 2000 11:49:52 -0400
|
|
Message-ID: <26100.971711392@sss.pgh.pa.us>
|
|
From: Tom Lane <tgl@sss.pgh.pa.us>
|
|
X-Mailing-List: pgsql-hackers@postgresql.org
|
|
Precedence: bulk
|
|
Sender: pgsql-hackers-owner@hub.org
|
|
Status: RO
|
|
Content-Length: 947
|
|
Lines: 19
|
|
|
|
Bruce Momjian <pgman@candle.pha.pa.us> writes:
|
|
>> It looks like it wouldn't take too much work to replace shared buffers
|
|
>> on the basis of LRU-2 instead of LRU, so I'm thinking about trying it.
|
|
>>
|
|
>> Has anyone looked into this area? Is there a better method to try?
|
|
|
|
> Sounds like a perfect idea. Good luck. :-)
|
|
|
|
Actually, the idea went down in flames :-(, but I neglected to report
|
|
back to pghackers about it. I did do some code to manage buffers as
|
|
LRU-2. I didn't have any good performance test cases to try it with,
|
|
but Richard Brosnahan was kind enough to re-run the TPC tests previously
|
|
published by Great Bridge with that code in place. Wasn't any faster,
|
|
in fact possibly a little slower, likely due to the extra CPU time spent
|
|
on buffer freelist management. It's possible that other scenarios might
|
|
show a better result, but right now I feel pretty discouraged about the
|
|
LRU-2 idea and am not pursuing it.
|
|
|
|
regards, tom lane
|
|
|
|
|
|
From pgsql-hackers-owner+M3455@postgresql.org Fri Jan 19 13:18:12 2001
|
|
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|
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|
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|
|
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|
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|
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|
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id <DG1W4LRZ>; Fri, 19 Jan 2001 09:46:14 -0800
|
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Message-ID: <8F4C99C66D04D4118F580090272A7A234D329F@sectorbase1.sectorbase.com>
|
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From: "Mikheev, Vadim" <vmikheev@SECTORBASE.COM>
|
|
To: "'Tom Lane'" <tgl@sss.pgh.pa.us>, Bruce Momjian <pgman@candle.pha.pa.us>
|
|
Cc: pgsql-hackers@postgresql.org
|
|
Subject: RE: [HACKERS] Possible performance improvement: buffer replacemen
|
|
t policy
|
|
Date: Fri, 19 Jan 2001 10:07:27 -0800
|
|
MIME-Version: 1.0
|
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Content-Type: text/plain;
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charset="iso-8859-1"
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Sender: pgsql-hackers-owner@postgresql.org
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Status: RO
|
|
|
|
> > Tom, did we ever test this? I think we did and found that
|
|
> > it was the same or worse, right?
|
|
>
|
|
> I tried it and didn't see any noticeable improvement on the particular
|
|
> test case I was using, so I got discouraged and didn't pursue the idea
|
|
> further. I'd like to come back to it someday, though.
|
|
|
|
I don't know how much useful could be LRU-2 but with WAL we should try
|
|
to reuse undirty free buffers first, not dirty ones, just to postpone
|
|
writes as long as we can. (BTW, this is what Oracle does.)
|
|
So, we probably should put new unfree dirty buffer just before first
|
|
dirty one in LRU.
|
|
|
|
Vadim
|
|
|
|
From markw@mohawksoft.com Thu Jun 7 14:40:02 2001
|
|
Return-path: <markw@mohawksoft.com>
|
|
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|
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|
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|
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|
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|
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Message-ID: <3B1FC9CB.57C72AD6@mohawksoft.com>
|
|
Date: Thu, 07 Jun 2001 14:36:59 -0400
|
|
From: mlw <markw@mohawksoft.com>
|
|
X-Mailer: Mozilla 4.75 [en] (X11; U; Linux 2.4.2 i686)
|
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To: Bruce Momjian <pgman@candle.pha.pa.us>,
|
|
"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
|
|
Subject: Re: 7.2 items
|
|
References: <200106071503.f57F32n03924@candle.pha.pa.us>
|
|
Content-Type: text/plain; charset=us-ascii
|
|
Content-Transfer-Encoding: 7bit
|
|
Status: RO
|
|
|
|
Bruce Momjian wrote:
|
|
|
|
> > Bruce Momjian <pgman@candle.pha.pa.us> writes:
|
|
> >
|
|
> > > Here is a small list of big TODO items. I was wondering which ones
|
|
> > > people were thinking about for 7.2?
|
|
> >
|
|
> > A friend of mine wants to use PostgreSQL instead of Oracle for a large
|
|
> > application, but has run into a snag when speed comparisons looked
|
|
> > good until the Oracle folks added a couple of BITMAP indexes. I can't
|
|
> > recall seeing any discussion about that here -- are there any plans?
|
|
>
|
|
> It is not on our list and I am not sure what they do.
|
|
|
|
Do you have access to any Oracle Documentation? There is a good explanation
|
|
of them.
|
|
|
|
However, I will try to explain.
|
|
|
|
If you have a table, locations. It has 1,000,000 records.
|
|
|
|
In oracle you do this:
|
|
|
|
create bitmap index bitmap_foo on locations (state) ;
|
|
|
|
For each unique value of 'state' oracle will create a bitmap with 1,000,000
|
|
bits in it. With a one representing a match and a zero representing no
|
|
match. Record '0' in the table is represented by bit '0' in the bitmap,
|
|
record '1' is represented by bit '1', record two by bit '2' and so on.
|
|
|
|
In a table where comparatively few different values are to be indexed in a
|
|
large table, a bitmap index can be quite small and not suffer the N * log(N)
|
|
disk I/O most tree based indexes suffer. If the bitmap is fairly sparse or
|
|
dense (or have periods of denseness and sparseness), it can be compressed
|
|
very efficiently as well.
|
|
|
|
When the statement:
|
|
|
|
select * from locations where state = 'MA';
|
|
|
|
Is executed, the bitmap is read into memory in very few disk operations.
|
|
(Perhaps even as few as one or two). It is a simple operation of rifling
|
|
through the bitmap for '1's that indicate the record has the property,
|
|
'state' = 'MA';
|
|
|
|
|
|
From mascarm@mascari.com Thu Jun 7 15:36:25 2001
|
|
Return-path: <mascarm@mascari.com>
|
|
Received: from corvette.mascari.com (dhcp065-024-161-045.columbus.rr.com [65.24.161.45])
|
|
by candle.pha.pa.us (8.10.1/8.10.1) with ESMTP id f57JaOc21943
|
|
for <pgman@candle.pha.pa.us>; Thu, 7 Jun 2001 15:36:24 -0400 (EDT)
|
|
Received: from ferrari (ferrari.mascari.com [192.168.2.1])
|
|
by corvette.mascari.com (8.9.3/8.9.3) with SMTP id PAA25607;
|
|
Thu, 7 Jun 2001 15:29:31 -0400
|
|
Received: by localhost with Microsoft MAPI; Thu, 7 Jun 2001 15:34:18 -0400
|
|
Message-ID: <01C0EF67.5105D2E0.mascarm@mascari.com>
|
|
From: Mike Mascari <mascarm@mascari.com>
|
|
Reply-To: "mascarm@mascari.com" <mascarm@mascari.com>
|
|
To: "'mlw'" <markw@mohawksoft.com>, Bruce Momjian <pgman@candle.pha.pa.us>,
|
|
"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
|
|
Subject: RE: [HACKERS] Re: 7.2 items
|
|
Date: Thu, 7 Jun 2001 15:34:17 -0400
|
|
Organization: Mascari Development Inc.
|
|
X-Mailer: Microsoft Internet E-mail/MAPI - 8.0.0.4211
|
|
MIME-Version: 1.0
|
|
Content-Type: text/plain; charset="us-ascii"
|
|
Content-Transfer-Encoding: 7bit
|
|
Status: RO
|
|
|
|
And in addition,
|
|
|
|
If you submitted the query:
|
|
|
|
SELECT * FROM addresses WHERE state = 'OH'
|
|
AND areacode = '614'
|
|
|
|
Then, with bitmap indexes, the bitmaps are just logically ANDed
|
|
together, and the final bitmap determines the matching rows.
|
|
|
|
Mike Mascari
|
|
mascarm@mascari.com
|
|
|
|
-----Original Message-----
|
|
From: mlw [SMTP:markw@mohawksoft.com]
|
|
|
|
Bruce Momjian wrote:
|
|
|
|
> > Bruce Momjian <pgman@candle.pha.pa.us> writes:
|
|
> >
|
|
> > > Here is a small list of big TODO items. I was wondering which
|
|
ones
|
|
> > > people were thinking about for 7.2?
|
|
> >
|
|
> > A friend of mine wants to use PostgreSQL instead of Oracle for a
|
|
large
|
|
> > application, but has run into a snag when speed comparisons
|
|
looked
|
|
> > good until the Oracle folks added a couple of BITMAP indexes. I
|
|
can't
|
|
> > recall seeing any discussion about that here -- are there any
|
|
plans?
|
|
>
|
|
> It is not on our list and I am not sure what they do.
|
|
|
|
Do you have access to any Oracle Documentation? There is a good
|
|
explanation
|
|
of them.
|
|
|
|
However, I will try to explain.
|
|
|
|
If you have a table, locations. It has 1,000,000 records.
|
|
|
|
In oracle you do this:
|
|
|
|
create bitmap index bitmap_foo on locations (state) ;
|
|
|
|
For each unique value of 'state' oracle will create a bitmap with
|
|
1,000,000
|
|
bits in it. With a one representing a match and a zero representing
|
|
no
|
|
match. Record '0' in the table is represented by bit '0' in the
|
|
bitmap,
|
|
record '1' is represented by bit '1', record two by bit '2' and so
|
|
on.
|
|
|
|
In a table where comparatively few different values are to be indexed
|
|
in a
|
|
large table, a bitmap index can be quite small and not suffer the N *
|
|
log(N)
|
|
disk I/O most tree based indexes suffer. If the bitmap is fairly
|
|
sparse or
|
|
dense (or have periods of denseness and sparseness), it can be
|
|
compressed
|
|
very efficiently as well.
|
|
|
|
When the statement:
|
|
|
|
select * from locations where state = 'MA';
|
|
|
|
Is executed, the bitmap is read into memory in very few disk
|
|
operations.
|
|
(Perhaps even as few as one or two). It is a simple operation of
|
|
rifling
|
|
through the bitmap for '1's that indicate the record has the
|
|
property,
|
|
'state' = 'MA';
|
|
|
|
|
|
|
|
From oleg@sai.msu.su Thu Jun 7 15:39:15 2001
|
|
Return-path: <oleg@sai.msu.su>
|
|
Received: from ra.sai.msu.su (ra.sai.msu.su [158.250.29.2])
|
|
by candle.pha.pa.us (8.10.1/8.10.1) with ESMTP id f57Jd7c22010
|
|
for <pgman@candle.pha.pa.us>; Thu, 7 Jun 2001 15:39:08 -0400 (EDT)
|
|
Received: from ra (ra [158.250.29.2])
|
|
by ra.sai.msu.su (8.9.3/8.9.3) with ESMTP id WAA07783;
|
|
Thu, 7 Jun 2001 22:38:20 +0300 (GMT)
|
|
Date: Thu, 7 Jun 2001 22:38:20 +0300 (GMT)
|
|
From: Oleg Bartunov <oleg@sai.msu.su>
|
|
X-X-Sender: <megera@ra.sai.msu.su>
|
|
To: mlw <markw@mohawksoft.com>
|
|
cc: Bruce Momjian <pgman@candle.pha.pa.us>,
|
|
"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
|
|
Subject: Re: [HACKERS] Re: 7.2 items
|
|
In-Reply-To: <3B1FC9CB.57C72AD6@mohawksoft.com>
|
|
Message-ID: <Pine.GSO.4.33.0106072234120.6015-100000@ra.sai.msu.su>
|
|
MIME-Version: 1.0
|
|
Content-Type: TEXT/PLAIN; charset=US-ASCII
|
|
Status: RO
|
|
|
|
I think it's possible to implement bitmap indexes with a little
|
|
effort using GiST. at least I know one implementation
|
|
http://www.it.iitb.ernet.in/~rvijay/dbms/proj/
|
|
if you have interests you could implement bitmap indexes yourself
|
|
unfortunately, we're very busy
|
|
|
|
Oleg
|
|
On Thu, 7 Jun 2001, mlw wrote:
|
|
|
|
> Bruce Momjian wrote:
|
|
>
|
|
> > > Bruce Momjian <pgman@candle.pha.pa.us> writes:
|
|
> > >
|
|
> > > > Here is a small list of big TODO items. I was wondering which ones
|
|
> > > > people were thinking about for 7.2?
|
|
> > >
|
|
> > > A friend of mine wants to use PostgreSQL instead of Oracle for a large
|
|
> > > application, but has run into a snag when speed comparisons looked
|
|
> > > good until the Oracle folks added a couple of BITMAP indexes. I can't
|
|
> > > recall seeing any discussion about that here -- are there any plans?
|
|
> >
|
|
> > It is not on our list and I am not sure what they do.
|
|
>
|
|
> Do you have access to any Oracle Documentation? There is a good explanation
|
|
> of them.
|
|
>
|
|
> However, I will try to explain.
|
|
>
|
|
> If you have a table, locations. It has 1,000,000 records.
|
|
>
|
|
> In oracle you do this:
|
|
>
|
|
> create bitmap index bitmap_foo on locations (state) ;
|
|
>
|
|
> For each unique value of 'state' oracle will create a bitmap with 1,000,000
|
|
> bits in it. With a one representing a match and a zero representing no
|
|
> match. Record '0' in the table is represented by bit '0' in the bitmap,
|
|
> record '1' is represented by bit '1', record two by bit '2' and so on.
|
|
>
|
|
> In a table where comparatively few different values are to be indexed in a
|
|
> large table, a bitmap index can be quite small and not suffer the N * log(N)
|
|
> disk I/O most tree based indexes suffer. If the bitmap is fairly sparse or
|
|
> dense (or have periods of denseness and sparseness), it can be compressed
|
|
> very efficiently as well.
|
|
>
|
|
> When the statement:
|
|
>
|
|
> select * from locations where state = 'MA';
|
|
>
|
|
> Is executed, the bitmap is read into memory in very few disk operations.
|
|
> (Perhaps even as few as one or two). It is a simple operation of rifling
|
|
> through the bitmap for '1's that indicate the record has the property,
|
|
> 'state' = 'MA';
|
|
>
|
|
>
|
|
> ---------------------------(end of broadcast)---------------------------
|
|
> TIP 6: Have you searched our list archives?
|
|
>
|
|
> http://www.postgresql.org/search.mpl
|
|
>
|
|
|
|
Regards,
|
|
Oleg
|
|
_____________________________________________________________
|
|
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
|
|
Sternberg Astronomical Institute, Moscow University (Russia)
|
|
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
|
|
phone: +007(095)939-16-83, +007(095)939-23-83
|
|
|
|
|
|
From pgsql-general-owner+M2497@hub.org Fri Jun 16 18:31:03 2000
|
|
Received: from renoir.op.net (root@renoir.op.net [207.29.195.4])
|
|
by candle.pha.pa.us (8.9.0/8.9.0) with ESMTP id RAA04165
|
|
for <pgman@candle.pha.pa.us>; Fri, 16 Jun 2000 17:31:01 -0400 (EDT)
|
|
Received: from hub.org (root@hub.org [216.126.84.1]) by renoir.op.net (o1/$Revision: 1.11 $) with ESMTP id RAA13110 for <pgman@candle.pha.pa.us>; Fri, 16 Jun 2000 17:20:12 -0400 (EDT)
|
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|
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|
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|
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|
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|
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|
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|
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|
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|
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(envelope-from giles@nemeton.com.au)
|
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Received: (qmail 10213 invoked from network); 16 Jun 2000 09:52:29 -0000
|
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Received: from nemeton.com.au (203.8.3.17)
|
|
by nemeton.com.au with SMTP; 16 Jun 2000 09:52:29 -0000
|
|
To: Jurgen Defurne <defurnj@glo.be>
|
|
cc: Mark Stier <kalium@gmx.de>,
|
|
postgreSQL general mailing list <pgsql-general@postgresql.org>
|
|
Subject: Re: [GENERAL] optimization by removing the file system layer?
|
|
In-Reply-To: Message from Jurgen Defurne <defurnj@glo.be>
|
|
of "Thu, 15 Jun 2000 20:26:57 +0200." <39491FF1.E1E583F8@glo.be>
|
|
Date: Fri, 16 Jun 2000 19:52:28 +1000
|
|
Message-ID: <10210.961149148@nemeton.com.au>
|
|
From: Giles Lean <giles@nemeton.com.au>
|
|
X-Mailing-List: pgsql-general@postgresql.org
|
|
Precedence: bulk
|
|
Sender: pgsql-general-owner@hub.org
|
|
Status: OR
|
|
|
|
|
|
|
|
> I think that the Un*x filesystem is one of the reasons that large
|
|
> database vendors rather use raw devices, than filesystem storage
|
|
> files.
|
|
|
|
This used to be the preference, back in the late 80s and possibly
|
|
early 90s. I'm seeing a preference toward using the filesystem now,
|
|
possibly with some sort of async I/O and co-operation from the OS
|
|
filesystem about interactions with the filesystem cache.
|
|
|
|
Performance preferences don't stand still. The hardware changes, the
|
|
software changes, the volume of data changes, and different solutions
|
|
become preferable.
|
|
|
|
> Using a raw device on the disk gives them the possibility to have
|
|
> complete control over their files, indices and objects without being
|
|
> bothered by the operating system.
|
|
>
|
|
> This speeds up things in several ways :
|
|
> - the least possible OS intervention
|
|
|
|
Not that this is especially useful, necessarily. If the "raw" device
|
|
is in fact managed by a logical volume manager doing mirroring onto
|
|
some sort of storage array there is still plenty of OS code involved.
|
|
|
|
The cost of using a filesystem in addition may not be much if anything
|
|
and of course a filesystem is considerably more flexible to
|
|
administer (backup, move, change size, check integrity, etc.)
|
|
|
|
> - choose block sizes according to applications
|
|
> - reducing fragmentation
|
|
> - packing data in nearby cilinders
|
|
|
|
... but when this storage area is spread over multiple mechanisms in a
|
|
smart storage array with write caching, you've no idea what is where
|
|
anyway. Better to let the hardware or at least the OS manage this;
|
|
there are so many levels of caching between a database and the
|
|
magnetic media that working hard to influence layout is almost
|
|
certainly a waste of time.
|
|
|
|
Kirk McKusick tells a lovely story that once upon a time it used to be
|
|
sensible to check some registers on a particular disk controller to
|
|
find out where the heads were when scheduling I/O. Needless to say,
|
|
that is history now!
|
|
|
|
There's a considerable cost in complexity and code in using "raw"
|
|
storage too, and it's not a one off cost: as the technologies change,
|
|
the "fast" way to do things will change and the code will have to be
|
|
updated to match. Better to leave this to the OS vendor where
|
|
possible, and take advantage of the tuning they do.
|
|
|
|
> - Anyone other ideas -> the sky is the limit here
|
|
|
|
> It also aids portability, at least on platforms that have an
|
|
> equivalent of a raw device.
|
|
|
|
I don't understand that claim. Not much is portable about raw
|
|
devices, and they're typically not nearlly as well documented as the
|
|
filesystem interfaces.
|
|
|
|
> It is also independent of the standard implemented Un*x filesystems,
|
|
> for which you will have to pay extra if you want to take extra
|
|
> measures against power loss.
|
|
|
|
Rather, it is worse. With a Unix filesystem you get quite defined
|
|
semantics about what is written when.
|
|
|
|
> The problem with e.g. e2fs, is that it is not robust enough if a CPU
|
|
> fails.
|
|
|
|
ext2fs doesn't even claim to have Unix filesystem semantics.
|
|
|
|
Regards,
|
|
|
|
Giles
|
|
|
|
|
|
|
|
From pgsql-hackers-owner+M1795@postgresql.org Thu Dec 7 18:47:52 2000
|
|
Received: from mail.postgresql.org (webmail.postgresql.org [216.126.85.28])
|
|
by candle.pha.pa.us (8.9.0/8.9.0) with ESMTP id SAA09172
|
|
for <pgman@candle.pha.pa.us>; Thu, 7 Dec 2000 18:47:52 -0500 (EST)
|
|
Received: from mail.postgresql.org (webmail.postgresql.org [216.126.85.28])
|
|
by mail.postgresql.org (8.11.1/8.11.1) with SMTP id eB7NjFP10612;
|
|
Thu, 7 Dec 2000 18:45:15 -0500 (EST)
|
|
(envelope-from pgsql-hackers-owner+M1795@postgresql.org)
|
|
Received: from thor.tht.net (thor.tht.net [209.47.145.4])
|
|
by mail.postgresql.org (8.11.1/8.11.1) with ESMTP id eB7N6BP08233
|
|
for <pgsql-hackers@postgresql.org>; Thu, 7 Dec 2000 18:06:11 -0500 (EST)
|
|
(envelope-from bright@fw.wintelcom.net)
|
|
Received: from fw.wintelcom.net (bright@ns1.wintelcom.net [209.1.153.20])
|
|
by thor.tht.net (8.9.3/8.9.3) with ESMTP id SAA97456
|
|
for <pgsql-hackers@postgresql.org>; Thu, 7 Dec 2000 18:57:32 GMT
|
|
(envelope-from bright@fw.wintelcom.net)
|
|
Received: (from bright@localhost)
|
|
by fw.wintelcom.net (8.10.0/8.10.0) id eB7MvWE21269
|
|
for pgsql-hackers@postgresql.org; Thu, 7 Dec 2000 14:57:32 -0800 (PST)
|
|
Date: Thu, 7 Dec 2000 14:57:32 -0800
|
|
From: Alfred Perlstein <bright@wintelcom.net>
|
|
To: pgsql-hackers@postgresql.org
|
|
Subject: [HACKERS] Patches with vacuum fixes available for 7.0.x
|
|
Message-ID: <20001207145732.X16205@fw.wintelcom.net>
|
|
MIME-Version: 1.0
|
|
Content-Type: text/plain; charset=us-ascii
|
|
Content-Disposition: inline
|
|
User-Agent: Mutt/1.2.5i
|
|
Precedence: bulk
|
|
Sender: pgsql-hackers-owner@postgresql.org
|
|
Status: ORr
|
|
|
|
We recently had a very satisfactory contract completed by
|
|
Vadim.
|
|
|
|
Basically Vadim has been able to reduce the amount of time
|
|
taken by a vacuum from 10-15 minutes down to under 10 seconds.
|
|
|
|
We've been running with these patches under heavy load for
|
|
about a week now without any problems except one:
|
|
don't 'lazy' (new option for vacuum) a table which has just
|
|
had an index created on it, or at least don't expect it to
|
|
take any less time than a normal vacuum would.
|
|
|
|
There's three patchsets and they are available at:
|
|
|
|
http://people.freebsd.org/~alfred/vacfix/
|
|
|
|
complete diff:
|
|
http://people.freebsd.org/~alfred/vacfix/v.diff
|
|
|
|
only lazy vacuum option to speed up index vacuums:
|
|
http://people.freebsd.org/~alfred/vacfix/vlazy.tgz
|
|
|
|
only lazy vacuum option to only scan from start of modified
|
|
data:
|
|
http://people.freebsd.org/~alfred/vacfix/mnmb.tgz
|
|
|
|
Although the patches are for 7.0.x I'm hoping that they
|
|
can be forward ported (if Vadim hasn't done it already)
|
|
to 7.1.
|
|
|
|
enjoy!
|
|
|
|
--
|
|
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
|
|
"I have the heart of a child; I keep it in a jar on my desk."
|
|
|
|
From pgsql-hackers-owner+M1809@postgresql.org Thu Dec 7 20:27:39 2000
|
|
Received: from mail.postgresql.org (webmail.postgresql.org [216.126.85.28])
|
|
by candle.pha.pa.us (8.9.0/8.9.0) with ESMTP id UAA11827
|
|
for <pgman@candle.pha.pa.us>; Thu, 7 Dec 2000 20:27:38 -0500 (EST)
|
|
Received: from mail.postgresql.org (webmail.postgresql.org [216.126.85.28])
|
|
by mail.postgresql.org (8.11.1/8.11.1) with SMTP id eB81PsP22362;
|
|
Thu, 7 Dec 2000 20:25:54 -0500 (EST)
|
|
(envelope-from pgsql-hackers-owner+M1809@postgresql.org)
|
|
Received: from fw.wintelcom.net (ns1.wintelcom.net [209.1.153.20])
|
|
by mail.postgresql.org (8.11.1/8.11.1) with ESMTP id eB81JkP21783
|
|
for <pgsql-hackers@postgresql.org>; Thu, 7 Dec 2000 20:19:46 -0500 (EST)
|
|
(envelope-from bright@fw.wintelcom.net)
|
|
Received: (from bright@localhost)
|
|
by fw.wintelcom.net (8.10.0/8.10.0) id eB81JwU25447;
|
|
Thu, 7 Dec 2000 17:19:58 -0800 (PST)
|
|
Date: Thu, 7 Dec 2000 17:19:58 -0800
|
|
From: Alfred Perlstein <bright@wintelcom.net>
|
|
To: Tom Lane <tgl@sss.pgh.pa.us>
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cc: pgsql-hackers@postgresql.org
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Subject: Re: [HACKERS] Patches with vacuum fixes available for 7.0.x
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Message-ID: <20001207171958.B16205@fw.wintelcom.net>
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References: <20001207145732.X16205@fw.wintelcom.net> <28791.976236143@sss.pgh.pa.us>
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In-Reply-To: <28791.976236143@sss.pgh.pa.us>; from tgl@sss.pgh.pa.us on Thu, Dec 07, 2000 at 07:42:23PM -0500
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Precedence: bulk
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Status: OR
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* Tom Lane <tgl@sss.pgh.pa.us> [001207 17:10] wrote:
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> Alfred Perlstein <bright@wintelcom.net> writes:
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> > Basically Vadim has been able to reduce the amount of time
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> > taken by a vacuum from 10-15 minutes down to under 10 seconds.
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>
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> Cool. What's it do, exactly?
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================================================================
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The first is a bonus that Vadim gave us to speed up index
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vacuums, I'm not sure I understand it completely, but it
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work really well. :)
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here's the README he gave us:
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Vacuum LAZY index cleanup option
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LAZY vacuum option introduces new way of indices cleanup.
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Instead of reading entire index file to remove index tuples
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pointing to deleted table records, with LAZY option vacuum
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performes index scans using keys fetched from table record
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to be deleted. Vacuum checks each result returned by index
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scan if it points to target heap record and removes
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corresponding index tuple.
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This can greatly speed up indices cleaning if not so many
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table records were deleted/modified between vacuum runs.
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Vacuum uses new option on user' demand.
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New vacuum syntax is:
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vacuum [verbose] [analyze] [lazy] [table [(columns)]]
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================================================================
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The second is one of the suggestions I gave on the lists a while
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back, keeping track of the "last dirtied" block in the data files
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to only scan the tail end of the file for deleted rows, I think
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what he instead did was keep a table that holds all the modified
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blocks and vacuum only scans those:
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Minimal Number Modified Block (MNMB)
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This feature is to track MNMB of required tables with triggers
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to avoid reading unmodified table pages by vacuum. Triggers
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store MNMB in per-table files in specified directory
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($LIBDIR/contrib/mnmb by default) and create these files if not
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existed.
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Vacuum first looks up functions
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mnmb_getblock(Oid databaseId, Oid tableId)
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mnmb_setblock(Oid databaseId, Oid tableId, Oid block)
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in catalog. If *both* functions were found *and* there was no
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ANALYZE option specified then vacuum calls mnmb_getblock to obtain
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MNMB for table being vacuumed and starts reading this table from
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block number returned. After table was processed vacuum calls
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mnmb_setblock to update data in file to last table block number.
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Neither mnmb_getblock nor mnmb_setblock try to create file.
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If there was no file for table being vacuumed then mnmb_getblock
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returns 0 and mnmb_setblock does nothing.
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mnmb_setblock() may be used to set in file MNMB to 0 and force
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vacuum to read entire table if required.
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To compile MNMB you have to add -DMNMB to CUSTOM_COPT
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in src/Makefile.custom.
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--
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-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
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"I have the heart of a child; I keep it in a jar on my desk."
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From pgsql-general-owner+M4010@postgresql.org Mon Feb 5 18:50:47 2001
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for pgsql-general@postgresql.org; Tue, 30 Jan 2001 19:27:10 -0500 (EST)
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(envelope-from news)
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From: Mike Hoskins <mikehoskins@yahoo.com>
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X-Newsgroups: comp.databases.postgresql.general
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Subject: Re: [GENERAL] MySQL file system
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Date: Tue, 30 Jan 2001 18:30:36 -0600
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Status: OR
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This idea is such a popular (even old) one that Oracle developed it for 8i --
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IFS. Yep, AS/400 has had it forever, and BeOS is another example. Informix has
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had its DataBlades for years, as well. In fact, Reiser-FS is an FS implemented
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on a DB, albeit probably not a SQL DB. AIX's LVM and JFS is extent/DB-based, as
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well. Let's see now, why would all those guys do that? (Now, some of those that
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aren't SQL-based probably won't allow SQL queries on files, so just think about
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those that do, for a minute)....
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Rather than asking why, a far better question is why not? There is SO much
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functionality to be gained here that it's silly to ask why. At a higher level,
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treating BLOBs as files and as DB entries simultaneously has so many uses, that
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one has trouble answering the question properly without the puzzled stare back
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at the questioner. Again, look at the above list, particularly at AS/400 -- the
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entire OS's FS sits on top of DB/2!
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For example, think how easy dynamically generated web sites could access online
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catalog information, with all those JPEG's, GIFs, PNGs, HTML files, Text files,
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.PDF's, etc., both in the DB and in the FS. This would be so much easier to
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maintain, when you have webmasters, web designers, artists, programmers,
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sysadmins, dba's, etc., all trying to manage a big, dynamic, graphics-rich web
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site. Who cares if the FS is a bit slow, as long as it's not too slow? That's
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not the point, anyway.
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The point is easy access to data: asset management, version control, the
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ability to access the same data as a file and as a BLOB simultaneously, the
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ability to replicate easier, the ability to use more tools on the same info,
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etc. It's not for speed, per se; instead, it's for accessibility.
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Think about this issue. You have some already compiled text-based program that
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works on binary files, but not on databases -- it was simply never designed into
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the program. How are you going to get your graphics BLOBs into that program?
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Oh yeah, let's write another program to transform our data into files, first,
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then after processing delete them in some cleanup routine.... Why? If you have
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a DB'ed FS, then file data can simultaneously have two views -- one for the DB
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and one as an FS. (You can easily reverse the scenario.) Not only does this
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save time and disk space; it saves you from having to pay for the most expensive
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element of all -- programmer time.
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BTW, once this FS-on-a-DB concept really sinks in, imagine how tightly
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integrated Linux/Unix apps could be written. Imagine if a bunch of GPL'ed
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software started coding for this and used this as a means to exchange data, all
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using a common set of libraries. You could get to the point of uniting files,
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BLOBs, data of all sorts, IPC, version control, etc., all under one umbrella,
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especially if XML was the means data was exchanged. Heck, distributed
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authentication, file access, data access, etc., could be improved greatly.
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Well, this paragraph sounds like flame bait, but really consider the
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ramifications. Also, read the next paragraph....
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Something like this *has* existed for Postgres for a long time -- PGFS, by Brian
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Bartholomew. It's even supposedly matured with age. Unfortunately, I cannot
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get to http://www.wv.com/ (Working Version's main site). Working Version is a
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version control system that keeps old versions of files around in the FS. It
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uses PG as the back-end DB and lets you mount it like another FS. It's
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supposedly an awesome system, but where is it? It's not some clunky korbit
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thingy, either. (If someone can find it, please let me know by email, if
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possible.)
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The only thing I can find on this is from a Google search, which caches
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everything but the actual software:
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http://www.google.com/search?q=pgfs+postgres&num=100&hl=en&lr=lang_en&newwindow=1&safe=active
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Also, there is the Perl-FS that can be transformed into something like PGFS:
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http://www.assurdo.com/perlfs/ It allows you to write Perl code that can mount
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various protocols or data types as an FS, in user space. (One example is the
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ability to mount FTP sites, BTW.)
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Instead of ridiculing something you've never tried, consider that MySQL-FS,
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Oracle (IFS), Informix (DataBlades), AS/400 (DB/2), BeOS, and Reiser-FS are
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doing this today. Do you want to be left behind and let them tell us what it's
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good for? Or, do we want this for PG? (Reiser-FS, BTW, is FASTER than ext2,
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but has no SQL hooks).
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There were many posts on this on slashdot:
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http://slashdot.org/article.pl?sid=01/01/16/1855253&mode=thread
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(I wrote some comments here, as well, just look for mikehoskins)
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I, for one, want to see this succeed for MySQL, PostgreSQL, msql, etc. It's an
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awesome feature that doesn't need to be speedy because it can save HUMANS time.
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The question really is, "When do we want to catch up to everyone else?" We are
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always moving to higher levels of abstraction, anyway, so it's just a matter of
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time. PG should participate.
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Adam Lang wrote:
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> I wasn't following the thread too closely, but database for a filesystem has
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> been done. BeOS uses a database for a filesystem as well as AS/400 and
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> Mainframes.
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>
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> Adam Lang
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> Systems Engineer
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> Rutgers Casualty Insurance Company
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> http://www.rutgersinsurance.com
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> ----- Original Message -----
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> From: "Alfred Perlstein" <bright@wintelcom.net>
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> To: "Robert D. Nelson" <RDNELSON@co.centre.pa.us>
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> Cc: "Joseph Shraibman" <jks@selectacast.net>; "Karl DeBisschop"
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> <karl@debisschop.net>; "Ned Lilly" <ned@greatbridge.com>; "PostgreSQL
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> General" <pgsql-general@postgresql.org>
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> Sent: Wednesday, January 17, 2001 12:23 PM
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> Subject: Re: [GENERAL] MySQL file system
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>
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> > * Robert D. Nelson <RDNELSON@co.centre.pa.us> [010117 05:17] wrote:
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> > > >Raw disk access allows:
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> > >
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> > > If I'm correct, mysql is providing a filesystem, not a way to access raw
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> > > disk, like Oracle does. Huge difference there - with a filesystem, you
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> have
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> > > overhead of FS *and* SQL at the same time.
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> >
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> > Oh, so it's sort of like /proc for mysql?
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> >
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> > What a terrible waste of time and resources. :(
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> >
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> > --
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> > -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
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> > "I have the heart of a child; I keep it in a jar on my desk."
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From pgsql-general-owner+M4049@postgresql.org Tue Feb 6 01:26:19 2001
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Date: Tue, 06 Feb 2001 14:15:55 +0800
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To: Mike Hoskins <mikehoskins@yahoo.com>, pgsql-general@postgresql.org
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From: Lincoln Yeoh <lyeoh@pop.jaring.my>
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Subject: [GENERAL] Re: MySQL file system
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In-Reply-To: <3A775CF7.3C5F1909@yahoo.com>
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Status: OR
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What you're saying seems to be to have a data structure where the same data
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can be accessed in both the filesystem style and the RDBMs style. How does
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that work? How is the mapping done between both structures? Slapping a
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filesystem on top of a RDBMs doesn't do that does it?
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Most filesystems are basically databases already, just differently
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structured and featured databases. And so far most of them do their job
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pretty well. You move a folder/directory somewhere, and everything inside
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it moves. Tons of data are already arranged in that form. Though porting
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over data from one filesystem to another is not always straightforward,
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RDBMSes are far worse.
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Maybe what would be nice is not a filesystem based on a database, rather
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one influenced by databases. One with a decent fulltextindex for data and
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filenames, where you have the option to ignore or not ignore
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nonalphanumerics and still get an indexed search.
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Then perhaps we could do something like the following:
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select file.name from path "/var/logs/" where file.name like "%.log%' and
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file.lastmodified > '2000/1/1' and file.contents =~ 'te_st[0-9]+\.gif$' use
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index
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Checkpoints would be nice too. Then I can rollback to a known point if I
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screw up ;).
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In fact the SQL style interface doesn't have to be built in at all. Neither
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does the index have to be realtime. I suppose there could be an option to
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make it realtime if performance is not an issue.
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What could be done is to use some fast filesystem. Then we add tools to
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maintain indexes, for SQL style interfaces and other style interfaces.
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Checkpoints and rollbacks would be harder of course.
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Cheerio,
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Link.
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