虽然select datname, xact_commit from pg_stat_database;按@Jack Douglas的建议使用时效果不佳（显然是由于自动真空），select datname, tup_inserted, tup_updated, tup_deleted from pg_stat_database但确实可以使用。DML和DDL更改都会更改tup_ *列的值，而a vacuum不会（vacuum analyze另一方面...）。
如果这可能对其他人有用，那么我会包括已经放置的备份脚本。这适用于Pg 8.4.x，但不适用于8.2.x-YMMV，具体取决于所用Pg的版本。
#!/usr/bin/env perl
=head1 Synopsis
pg_backup -- selectively backup a postgresql database cluster
=head1 Description
Perform backups (pg_dump*) of postgresql databases in a cluster on an
as needed basis.
For some database clusters, there may be databases that are:
a. rarely updated/changed and therefore shouldn't require dumping as
often as those databases that are frequently changed/updated.
b. are large enough that dumping them without need is undesirable.
The global data is always dumped without regard to whether any
individual databses need backing up or not.
=head1 Usage
pg_backup [OPTION]...
General options:
-F, --format=c|t|p output file format for data dumps
(custom, tar, plain text) (default is custom)
-a, --all backup (pg_dump) all databases in the cluster
(default is to only pg_dump databases that have
changed since the last backup)
--backup-dir directory to place backup files in
(default is ./backups)
-v, --verbose verbose mode
--help show this help, then exit
Connection options:
-h, --host=HOSTNAME database server host or socket directory
-p, --port=PORT database server port number
-U, --username=NAME connect as specified database user
-d, --database=NAME connect to database name for global data
=head1 Notes
This utility has been developed against PostgreSQL version 8.4.x. Older
versions of PostgreSQL may not work.
`vacuum` does not appear to trigger a backup unless there is actually
something to vacuum whereas `vacuum analyze` appears to always trigger a
backup.
=head1 Copyright and License
Copyright (C) 2011 by Gregory Siems
This library is free software; you can redistribute it and/or modify it
under the same terms as PostgreSQL itself, either PostgreSQL version
8.4 or, at your option, any later version of PostgreSQL you may have
available.
=cut
use strict;
use warnings;
use Getopt::Long;
use Data::Dumper;
use POSIX qw(strftime);
my %opts = get_options();
my $connect_options = '';
$connect_options .= "--$_=$opts{$_} " for (qw(username host port));
my $shared_dump_args = ($opts{verbose})
? $connect_options . ' --verbose '
: $connect_options;
my $backup_prefix = (exists $opts{host} && $opts{host} ne 'localhost')
? $opts{backup_dir} . '/' . $opts{host} . '-'
: $opts{backup_dir} . '/';
do_main();
########################################################################
sub do_main {
backup_globals();
my $last_stats_file = $backup_prefix . 'last_stats';
# get the previous pg_stat_database data
my %last_stats;
if ( -f $last_stats_file) {
%last_stats = parse_stats (split "\n", slurp_file ($last_stats_file));
}
# get the current pg_stat_database data
my $cmd = 'psql ' . $connect_options;
$cmd .= " $opts{database} " if (exists $opts{database});
$cmd .= "-Atc \"
select date_trunc('minute', now()), datid, datname,
xact_commit, tup_inserted, tup_updated, tup_deleted
from pg_stat_database
where datname not in ('template0','template1','postgres'); \"";
$cmd =~ s/\ns+/ /g;
my @stats = `$cmd`;
my %curr_stats = parse_stats (@stats);
# do a backup if needed
foreach my $datname (sort keys %curr_stats) {
my $needs_backup = 0;
if ($opts{all}) {
$needs_backup = 1;
}
elsif ( ! exists $last_stats{$datname} ) {
$needs_backup = 1;
warn "no last stats for $datname\n" if ($opts{debug});
}
else {
for (qw (tup_inserted tup_updated tup_deleted)) {
if ($last_stats{$datname}{$_} != $curr_stats{$datname}{$_}) {
$needs_backup = 1;
warn "$_ stats do not match for $datname\n" if ($opts{debug});
}
}
}
if ($needs_backup) {
backup_db ($datname);
}
else {
chitchat ("Database \"$datname\" does not currently require backing up.");
}
}
# update the pg_stat_database data
open my $fh, '>', $last_stats_file || die "Could not open $last_stats_file for output. !$\n";
print $fh @stats;
close $fh;
}
sub parse_stats {
my @in = @_;
my %stats;
chomp @in;
foreach my $line (@in) {
my @ary = split /\|/, $line;
my $datname = $ary[2];
next unless ($datname);
foreach my $key (qw(tmsp datid datname xact_commit tup_inserted tup_updated tup_deleted)) {
my $val = shift @ary;
$stats{$datname}{$key} = $val;
}
}
return %stats;
}
sub backup_globals {
chitchat ("Backing up the global data.");
my $backup_file = $backup_prefix . 'globals-only.backup.gz';
my $cmd = 'pg_dumpall --globals-only ' . $shared_dump_args;
$cmd .= " --database=$opts{database} " if (exists $opts{database});
do_dump ($backup_file, "$cmd | gzip");
}
sub backup_db {
my $database = shift;
chitchat ("Backing up database \"$database\".");
my $backup_file = $backup_prefix . $database . '-schema-only.backup.gz';
do_dump ($backup_file, "pg_dump --schema-only --create --format=plain $shared_dump_args $database | gzip");
$backup_file = $backup_prefix . $database . '.backup';
do_dump ($backup_file, "pg_dump --format=". $opts{format} . " $shared_dump_args $database");
}
sub do_dump {
my ($backup_file, $cmd) = @_;
my $temp_file = $backup_file . '.new';
warn "Command is: $cmd > $temp_file" if ($opts{debug});
chitchat (`$cmd > $temp_file`);
if ( -f $temp_file ) {
chitchat (`mv $temp_file $backup_file`);
}
}
sub chitchat {
my @ary = @_;
return unless (@ary);
chomp @ary;
my $first = shift @ary;
my $now = strftime "%Y%m%d-%H:%M:%S", localtime;
print +(join "\n ", "$now $first", @ary), "\n";
}
sub get_options {
Getopt::Long::Configure('bundling');
my %opts = ();
GetOptions(
"a" => \$opts{all},
"all" => \$opts{all},
"p=s" => \$opts{port},
"port=s" => \$opts{port},
"U=s" => \$opts{username},
"username=s" => \$opts{username},
"h=s" => \$opts{host},
"host=s" => \$opts{host},
"F=s" => \$opts{format},
"format=s" => \$opts{format},
"d=s" => \$opts{database},
"database=s" => \$opts{database},
"backup-dir=s" => \$opts{backup_dir},
"help" => \$opts{help},
"v" => \$opts{verbose},
"verbose" => \$opts{verbose},
"debug" => \$opts{debug},
);
# Does the user need help?
if ($opts{help}) {
show_help();
}
$opts{host} ||= $ENV{PGHOSTADDR} || $ENV{PGHOST} || 'localhost';
$opts{port} ||= $ENV{PGPORT} || '5432';
$opts{host} ||= $ENV{PGHOST} || 'localhost';
$opts{username} ||= $ENV{PGUSER} || $ENV{USER} || 'postgres';
$opts{database} ||= $ENV{PGDATABASE} || $opts{username};
$opts{backup_dir} ||= './backups';
my %formats = (
c => 'custom',
custom => 'custom',
t => 'tar',
tar => 'tar',
p => 'plain',
plain => 'plain',
);
$opts{format} = (defined $opts{format})
? $formats{$opts{format}} || 'custom'
: 'custom';
warn Dumper \%opts if ($opts{debug});
return %opts;
}
sub show_help {
print `perldoc -F $0`;
exit;
}
sub slurp_file { local (*ARGV, $/); @ARGV = shift; <> }
__END__
更新：脚本已放在github 此处。