pg_amcheck: avoid unhelpful verification attempts.

Avoid calling contrib/amcheck functions with relations that are
unsuitable for checking.  Specifically, don't attempt verification of
temporary relations, or indexes whose pg_index entry indicates that the
index is invalid, or not ready.

These relations are not supported by any of the contrib/amcheck
functions, for reasons that are pretty fundamental.  For example, the
implementation of REINDEX CONCURRENTLY can add its own "transient"
pg_index entries, which has rather unclear implications for the B-Tree
verification functions, at least in the general case -- so they just
treat it as an error.  It falls to the amcheck caller (in this case
pg_amcheck) to deal with the situation at a higher level.

pg_amcheck now simply treats these conditions as additional "visibility
concerns" when it queries system catalogs.  This is a little arbitrary.
It seems to have the least problems among any of the available
alternatives.

Author: Mark Dilger <mark.dilger@enterprisedb.com>
Reported-By: Alexander Lakhin <exclusion@gmail.com>
Reviewed-By: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Robert Haas <robertmhaas@gmail.com>
Bug: #17212
Discussion: https://postgr.es/m/17212-34dd4a1d6bba98bf@postgresql.org
Backpatch: 14-, where pg_amcheck was introduced.
This commit is contained in:
Peter Geoghegan 2021-10-13 14:08:12 -07:00
parent 6df1543abf
commit d2bf06db37
3 changed files with 299 additions and 29 deletions

View File

@ -435,6 +435,18 @@ PostgreSQL documentation
</variablelist>
</para>
<warning>
<para>
The extra checks performed against B-tree indexes when the
<option>--parent-check</option> option or the
<option>--rootdescend</option> option is specified require
relatively strong relation-level locks. These checks are the only
checks that will block concurrent data modification from
<command>INSERT</command>, <command>UPDATE</command>, and
<command>DELETE</command> commands.
</para>
</warning>
<para>
The following command-line options control the connection to the server:

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@ -816,6 +816,9 @@ main(int argc, char *argv[])
* names matching the expectations of verify_heap_slot_handler, which will
* receive and handle each row returned from the verify_heapam() function.
*
* The constructed SQL command will silently skip temporary tables, as checking
* them would needlessly draw errors from the underlying amcheck function.
*
* sql: buffer into which the heap table checking command will be written
* rel: relation information for the heap table to be checked
* conn: the connection to be used, for string escaping purposes
@ -825,10 +828,10 @@ prepare_heap_command(PQExpBuffer sql, RelationInfo *rel, PGconn *conn)
{
resetPQExpBuffer(sql);
appendPQExpBuffer(sql,
"SELECT blkno, offnum, attnum, msg FROM %s.verify_heapam("
"\nrelation := %u, on_error_stop := %s, check_toast := %s, skip := '%s'",
"SELECT v.blkno, v.offnum, v.attnum, v.msg "
"FROM pg_catalog.pg_class c, %s.verify_heapam("
"\nrelation := c.oid, on_error_stop := %s, check_toast := %s, skip := '%s'",
rel->datinfo->amcheck_schema,
rel->reloid,
opts.on_error_stop ? "true" : "false",
opts.reconcile_toast ? "true" : "false",
opts.skip);
@ -838,7 +841,10 @@ prepare_heap_command(PQExpBuffer sql, RelationInfo *rel, PGconn *conn)
if (opts.endblock >= 0)
appendPQExpBuffer(sql, ", endblock := " INT64_FORMAT, opts.endblock);
appendPQExpBufferChar(sql, ')');
appendPQExpBuffer(sql,
"\n) v WHERE c.oid = %u "
"AND c.relpersistence != 't'",
rel->reloid);
}
/*
@ -849,6 +855,10 @@ prepare_heap_command(PQExpBuffer sql, RelationInfo *rel, PGconn *conn)
* functions do not return any, but rather return corruption information by
* raising errors, which verify_btree_slot_handler expects.
*
* The constructed SQL command will silently skip temporary indexes, and
* indexes being reindexed concurrently, as checking them would needlessly draw
* errors from the underlying amcheck functions.
*
* sql: buffer into which the heap table checking command will be written
* rel: relation information for the index to be checked
* conn: the connection to be used, for string escaping purposes
@ -858,27 +868,31 @@ prepare_btree_command(PQExpBuffer sql, RelationInfo *rel, PGconn *conn)
{
resetPQExpBuffer(sql);
/*
* Embed the database, schema, and relation name in the query, so if the
* check throws an error, the user knows which relation the error came
* from.
*/
if (opts.parent_check)
appendPQExpBuffer(sql,
"SELECT * FROM %s.bt_index_parent_check("
"index := '%u'::regclass, heapallindexed := %s, "
"rootdescend := %s)",
"SELECT %s.bt_index_parent_check("
"index := c.oid, heapallindexed := %s, rootdescend := %s)"
"\nFROM pg_catalog.pg_class c, pg_catalog.pg_index i "
"WHERE c.oid = %u "
"AND c.oid = i.indexrelid "
"AND c.relpersistence != 't' "
"AND i.indisready AND i.indisvalid AND i.indislive",
rel->datinfo->amcheck_schema,
rel->reloid,
(opts.heapallindexed ? "true" : "false"),
(opts.rootdescend ? "true" : "false"));
(opts.rootdescend ? "true" : "false"),
rel->reloid);
else
appendPQExpBuffer(sql,
"SELECT * FROM %s.bt_index_check("
"index := '%u'::regclass, heapallindexed := %s)",
"SELECT %s.bt_index_check("
"index := c.oid, heapallindexed := %s)"
"\nFROM pg_catalog.pg_class c, pg_catalog.pg_index i "
"WHERE c.oid = %u "
"AND c.oid = i.indexrelid "
"AND c.relpersistence != 't' "
"AND i.indisready AND i.indisvalid AND i.indislive",
rel->datinfo->amcheck_schema,
rel->reloid,
(opts.heapallindexed ? "true" : "false"));
(opts.heapallindexed ? "true" : "false"),
rel->reloid);
}
/*
@ -1086,15 +1100,17 @@ verify_btree_slot_handler(PGresult *res, PGconn *conn, void *context)
if (PQresultStatus(res) == PGRES_TUPLES_OK)
{
int ntups = PQntuples(res);
int ntups = PQntuples(res);
if (ntups != 1)
if (ntups > 1)
{
/*
* We expect the btree checking functions to return one void row
* each, so we should output some sort of warning if we get
* anything else, not because it indicates corruption, but because
* it suggests a mismatch between amcheck and pg_amcheck versions.
* each, or zero rows if the check was skipped due to the object
* being in the wrong state to be checked, so we should output some
* sort of warning if we get anything more, not because it
* indicates corruption, but because it suggests a mismatch between
* amcheck and pg_amcheck versions.
*
* In conjunction with --progress, anything written to stderr at
* this time would present strangely to the user without an extra
@ -1889,10 +1905,16 @@ compile_relation_list_one_db(PGconn *conn, SimplePtrList *relations,
"\nAND (c.relam = %u OR NOT ep.btree_only OR ep.rel_regex IS NULL)",
HEAP_TABLE_AM_OID, BTREE_AM_OID);
/*
* Exclude temporary tables and indexes, which must necessarily belong to
* other sessions. (We don't create any ourselves.) We must ultimately
* exclude indexes marked invalid or not ready, but we delay that decision
* until firing off the amcheck command, as the state of an index may
* change by then.
*/
appendPQExpBufferStr(&sql, "\nWHERE c.relpersistence != 't'");
if (opts.excludetbl || opts.excludeidx || opts.excludensp)
appendPQExpBufferStr(&sql, "\nWHERE ep.pattern_id IS NULL");
else
appendPQExpBufferStr(&sql, "\nWHERE true");
appendPQExpBufferStr(&sql, "\nAND ep.pattern_id IS NULL");
/*
* We need to be careful not to break the --no-dependent-toast and
@ -1944,7 +1966,8 @@ compile_relation_list_one_db(PGconn *conn, SimplePtrList *relations,
"\nON ('pg_toast' ~ ep.nsp_regex OR ep.nsp_regex IS NULL)"
"\nAND (t.relname ~ ep.rel_regex OR ep.rel_regex IS NULL)"
"\nAND ep.heap_only"
"\nWHERE ep.pattern_id IS NULL");
"\nWHERE ep.pattern_id IS NULL"
"\nAND t.relpersistence != 't'");
appendPQExpBufferStr(&sql,
"\n)");
}
@ -1962,7 +1985,8 @@ compile_relation_list_one_db(PGconn *conn, SimplePtrList *relations,
"\nINNER JOIN pg_catalog.pg_index i "
"ON r.oid = i.indrelid "
"INNER JOIN pg_catalog.pg_class c "
"ON i.indexrelid = c.oid");
"ON i.indexrelid = c.oid "
"AND c.relpersistence != 't'");
if (opts.excludeidx || opts.excludensp)
appendPQExpBufferStr(&sql,
"\nINNER JOIN pg_catalog.pg_namespace n "
@ -2000,7 +2024,8 @@ compile_relation_list_one_db(PGconn *conn, SimplePtrList *relations,
"INNER JOIN pg_catalog.pg_index i "
"ON t.oid = i.indrelid"
"\nINNER JOIN pg_catalog.pg_class c "
"ON i.indexrelid = c.oid");
"ON i.indexrelid = c.oid "
"AND c.relpersistence != 't'");
if (opts.excludeidx)
appendPQExpBufferStr(&sql,
"\nLEFT OUTER JOIN exclude_pat ep "

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@ -0,0 +1,233 @@
# Copyright (c) 2021, PostgreSQL Global Development Group
# This regression test checks the behavior of pg_amcheck in the presence of
# inappropriate target relations.
#
use strict;
use warnings;
use PostgresNode;
use TestLib;
use Test::More tests => 52;
# Establish a primary and standby server, with temporary and unlogged tables.
# The temporary tables should not be checked on either system, as pg_amcheck's
# sessions won't be able to see their contents. The unlogged tables should not
# be checked on the standby, as they won't have relation forks there.
#
my $node_primary = PostgresNode->new('primary');
$node_primary->init(
allows_streaming => 1,
auth_extra => [ '--create-role', 'repl_role' ]);
$node_primary->start;
$node_primary->safe_psql('postgres', qq(
CREATE EXTENSION amcheck;
CREATE UNLOGGED TABLE unlogged_heap (i INTEGER[], b BOX);
INSERT INTO unlogged_heap (i, b) VALUES (ARRAY[1,2,3]::INTEGER[], '((1,2),(3,4))'::BOX);
CREATE INDEX unlogged_btree ON unlogged_heap USING BTREE (i);
CREATE INDEX unlogged_brin ON unlogged_heap USING BRIN (b);
CREATE INDEX unlogged_gin ON unlogged_heap USING GIN (i);
CREATE INDEX unlogged_gist ON unlogged_heap USING GIST (b);
CREATE INDEX unlogged_hash ON unlogged_heap USING HASH (i);
));
my $backup_name = 'my_backup';
$node_primary->backup($backup_name);
# Hold open a session with temporary tables and indexes defined
#
my $in = '';
my $out = '';
my $timer = IPC::Run::timeout(180);
my $h = $node_primary->background_psql('postgres', \$in, \$out, $timer);
$in = qq(
BEGIN;
CREATE TEMPORARY TABLE heap_temporary (i INTEGER[], b BOX) ON COMMIT PRESERVE ROWS;
INSERT INTO heap_temporary (i, b) VALUES (ARRAY[1,2,3]::INTEGER[], '((1,2),(3,4))'::BOX);
CREATE INDEX btree_temporary ON heap_temporary USING BTREE (i);
CREATE INDEX brin_temporary ON heap_temporary USING BRIN (b);
CREATE INDEX gin_temporary ON heap_temporary USING GIN (i);
CREATE INDEX gist_temporary ON heap_temporary USING GIST (b);
CREATE INDEX hash_temporary ON heap_temporary USING HASH (i);
COMMIT;
BEGIN;
);
$h->pump_nb;
my $node_standby = PostgresNode->new('standby');
$node_standby->init_from_backup($node_primary, $backup_name,
has_streaming => 1);
$node_standby->start;
$node_primary->wait_for_catchup($node_standby, 'replay',
$node_primary->lsn('replay'));
# Check that running amcheck functions from SQL against inappropriate targets
# fails sensibly. This portion of the test arguably belongs in contrib/amcheck
# rather than here, but we have already set up the necessary test environment,
# so check here rather than duplicating the environment there.
#
my ($stdout, $stderr);
for my $test (
[ $node_standby => "SELECT * FROM verify_heapam('unlogged_heap')",
qr/^$/,
"checking unlogged table during recovery does not complain" ],
[ $node_standby => "SELECT * FROM bt_index_check('unlogged_btree')",
qr/^$/,
"checking unlogged btree index during recovery does not complain" ],
[ $node_standby => "SELECT * FROM bt_index_check('unlogged_brin')",
qr/ERROR: only B-Tree indexes are supported as targets for verification.*DETAIL: Relation "unlogged_brin" is not a B-Tree index/s,
"checking unlogged brin index during recovery fails appropriately" ],
[ $node_standby => "SELECT * FROM bt_index_check('unlogged_gin')",
qr/ERROR: only B-Tree indexes are supported as targets for verification.*DETAIL: Relation "unlogged_gin" is not a B-Tree index/s,
"checking unlogged gin index during recovery fails appropriately" ],
[ $node_standby => "SELECT * FROM bt_index_check('unlogged_gist')",
qr/ERROR: only B-Tree indexes are supported as targets for verification.*DETAIL: Relation "unlogged_gist" is not a B-Tree index/s,
"checking unlogged gist index during recovery fails appropriately" ],
[ $node_standby => "SELECT * FROM bt_index_check('unlogged_hash')",
qr/ERROR: only B-Tree indexes are supported as targets for verification.*DETAIL: Relation "unlogged_hash" is not a B-Tree index/s,
"checking unlogged hash index during recovery fails appropriately" ],
)
{
$test->[0]->psql('postgres', $test->[1],
stdout => \$stdout, stderr => \$stderr);
like ($stderr, $test->[2], $test->[3]);
}
# Verify that --all excludes the temporary relations and handles unlogged
# relations as appropriate, without raising any warnings or exiting with a
# non-zero status.
#
$node_primary->command_checks_all(
['pg_amcheck', '--all', '-D', 'template1'],
0,
[ qr/^$/ ],
[ qr/^$/ ],
'pg_amcheck all objects on primary');
$node_standby->command_checks_all(
['pg_amcheck', '--all', '-D', 'template1'],
0,
[ qr/^$/ ],
[ qr/^$/ ],
'pg_amcheck all objects on standby');
# Verify that explicitly asking for unlogged relations to be checked does not
# raise any warnings or exit with a non-zero exit status, even when they cannot
# be checked due to recovery being in progress.
#
# These relations will have no relation fork during recovery, so even without
# checking them, we can say (by definition) that they are not corrupt, because
# it is meaningless to declare a non-existent relation fork corrupt.
#
$node_primary->command_checks_all(
['pg_amcheck', '--relation', '*unlogged*'],
0,
[ qr/^$/ ],
[ qr/^$/ ],
'pg_amcheck unlogged objects on primary');
$node_standby->command_checks_all(
['pg_amcheck', '--relation', '*unlogged*'],
0,
[ qr/^$/ ],
[ qr/^$/ ],
'pg_amcheck unlogged objects on standby');
# Verify that the --heapallindexed check works on both primary and standby.
#
$node_primary->command_checks_all(
['pg_amcheck', '--all', '-D', 'template1', '--heapallindexed'],
0,
[ qr/^$/ ],
[ qr/^$/ ],
'pg_amcheck --helpallindexed on primary');
$node_standby->command_checks_all(
['pg_amcheck', '--all', '-D', 'template1', '--heapallindexed'],
0,
[ qr/^$/ ],
[ qr/^$/ ],
'pg_amcheck --helpallindexed on standby');
# Verify that the --parent-check and --rootdescend options work on the primary.
#
$node_primary->command_checks_all(
['pg_amcheck', '--all', '-D', 'template1', '--rootdescend'],
0,
[ qr/^$/ ],
[ qr/^$/ ],
'pg_amcheck --rootdescend on primary');
$node_primary->command_checks_all(
['pg_amcheck', '--all', '-D', 'template1', '--parent-check'],
0,
[ qr/^$/ ],
[ qr/^$/ ],
'pg_amcheck --parent-check on primary');
# Check that the failures on the standby from using --parent-check and
# --rootdescend are the failures we expect
#
$node_standby->command_checks_all(
['pg_amcheck', '--all', '-D', 'template1', '--rootdescend'],
2,
[ qr/ERROR: cannot acquire lock mode ShareLock on database objects while recovery is in progress/,
qr/btree index "postgres\.pg_catalog\./,
qr/btree index "postgres\.pg_toast\./,
],
[ qr/^$/ ],
'pg_amcheck --rootdescend on standby');
$node_standby->command_checks_all(
['pg_amcheck', '--all', '-D', 'template1', '--parent-check'],
2,
[ qr/ERROR: cannot acquire lock mode ShareLock on database objects while recovery is in progress/,
qr/btree index "postgres\.pg_catalog\./,
qr/btree index "postgres\.pg_toast\./,
],
[ qr/^$/ ],
'pg_amcheck --parent-check on standby');
# Bug #17212
#
# Verify that explicitly asking for another session's temporary relations to be
# checked fails, but only in the sense that nothing matched the parameter. We
# don't complain that they are uncheckable, only that you gave a --relation
# option and we didn't find anything checkable matching the pattern.
#
$node_primary->command_checks_all(
['pg_amcheck', '--relation', '*temporary*'],
1,
[ qr/^$/ ],
[ qr/error: no relations to check matching "\*temporary\*"/ ],
'pg_amcheck temporary objects on primary');
$node_standby->command_checks_all(
['pg_amcheck', '--relation', '*temporary*'],
1,
[ qr/^$/ ],
[ qr/error: no relations to check matching "\*temporary\*"/ ],
'pg_amcheck temporary objects on standby');
# Verify that a relation pattern which only matches temporary relations draws
# an error, even when other relation patterns are ok. This differs from the
# test above in that the set of all relations to check is not empty.
#
$node_primary->command_checks_all(
['pg_amcheck', '--relation', '*temporary*', '--relation', '*unlogged*'],
1,
[ qr/^$/ ],
[ qr/error: no relations to check matching "\*temporary\*"/ ],
'pg_amcheck temporary objects on primary');
$node_standby->command_checks_all(
['pg_amcheck', '--relation', '*temporary*', '--relation', '*unlogged*'],
1,
[ qr/^$/ ],
[ qr/error: no relations to check matching "\*temporary\*"/ ],
'pg_amcheck temporary objects on standby');