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Optimize pg_visibility with read streams.

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We've measured 5% performance improvement, and this arranges to benefit
automatically from future optimizations to the read_stream subsystem.
The area lacked test coverage, so close that gap.

Nazir Bilal Yavuz

Discussion: https://postgr.es/m/CAN55FZ1_Ru3XpMgTwsU67FTH2fs_FrRROmb7x6zs+F44QBEiww@mail.gmail.com
Discussion: https://postgr.es/m/CAEudQAozv3wTY5TV2t29JcwPydbmKbiWQkZD42S2OgzdixPMDQ@mail.gmail.com
This commit is contained in:
Noah Misch
2024-09-10 15:21:33 -07:00
parent 52c707483c
commit 65c310b310
3 changed files with 202 additions and 21 deletions
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109
contrib/pg_visibility/t/002_corrupt_vm.pl Normal file
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# Copyright (c) 2021-2024, PostgreSQL Global Development Group
# Check that pg_check_visible() and pg_check_frozen() report correct TIDs for
# corruption.
use strict;
use warnings FATAL => 'all';
use File::Copy;
use PostgreSQL::Test::Cluster;
use PostgreSQL::Test::Utils;
use Test::More;
my $node = PostgreSQL::Test::Cluster->new('main');
$node->init;
# Anything holding a snapshot, including auto-analyze of pg_proc, could stop
# VACUUM from updating the visibility map.
$node->append_conf('postgresql.conf', 'autovacuum=off');
$node->start;
my $blck_size = $node->safe_psql("postgres", "SHOW block_size;");
# Create a sample table with at least 10 pages and then run VACUUM. 10 is
# selected manually as it is big enough to select 5 random tuples from the
# relation.
$node->safe_psql(
'postgres', qq(
CREATE EXTENSION pg_visibility;
CREATE TABLE corruption_test
WITH (autovacuum_enabled = false) AS
SELECT
i,
repeat('a', 10) AS data
FROM
generate_series(1, $blck_size) i;
VACUUM (FREEZE, DISABLE_PAGE_SKIPPING) corruption_test;
));
# VACUUM is run, it is safe to get the number of pages.
my $npages = $node->safe_psql(
"postgres",
"SELECT relpages FROM pg_class
WHERE relname = 'corruption_test';"
);
ok($npages >= 10, 'table has at least 10 pages');
my $file = $node->safe_psql("postgres",
"SELECT pg_relation_filepath('corruption_test');");
# Delete the first block to make sure that it will be skipped as it is
# not visible nor frozen.
$node->safe_psql(
"postgres",
"DELETE FROM corruption_test
WHERE (ctid::text::point)[0] = 0;"
);
# Copy visibility map.
$node->stop;
my $vm_file = $node->data_dir . '/' . $file . '_vm';
copy("$vm_file", "${vm_file}_temp");
$node->start;
# Select 5 random tuples that are starting from the second block of the
# relation. The first block is skipped because it is deleted above.
my $tuples = $node->safe_psql(
"postgres",
"SELECT ctid FROM (
SELECT ctid FROM corruption_test
WHERE (ctid::text::point)[0] != 0
ORDER BY random() LIMIT 5)
ORDER BY ctid ASC;"
);
# Do the changes below to use tuples in the query.
# "\n" -> ","
# "(" -> "'("
# ")" -> ")'"
(my $tuples_query = $tuples) =~ s/\n/,/g;
$tuples_query =~ s/\(/\'\(/g;
$tuples_query =~ s/\)/\)\'/g;
$node->safe_psql(
"postgres",
"DELETE FROM corruption_test
WHERE ctid in ($tuples_query);"
);
# Overwrite visibility map with the old one.
$node->stop;
move("${vm_file}_temp", "$vm_file");
$node->start;
my $result = $node->safe_psql(
"postgres",
"SELECT DISTINCT t_ctid
FROM pg_check_visible('corruption_test')
ORDER BY t_ctid ASC;"
);
is($result, $tuples, 'pg_check_visible must report tuples as corrupted');
$result = $node->safe_psql(
"postgres",
"SELECT DISTINCT t_ctid
FROM pg_check_frozen('corruption_test')
ORDER BY t_ctid ASC;"
);
is($result, $tuples, 'pg_check_frozen must report tuples as corrupted');
$node->stop;
done_testing();