pg_amcheck — checks for corruption in one or more PostgreSQL databases
pg_amcheck
[option
...] [dbname
]
pg_amcheck supports running amcheck's corruption checking functions against one or more databases, with options to select which schemas, tables and indexes to check, which kinds of checking to perform, and whether to perform the checks in parallel, and if so, the number of parallel connections to establish and use.
Only ordinary and toast table relations, materialized views, sequences, and btree indexes are currently supported. Other relation types are silently skipped.
If dbname
is specified, it should be the name of a
single database to check, and no other database selection options should
be present. Otherwise, if any database selection options are present,
all matching databases will be checked. If no such options are present,
the default database will be checked. Database selection options include
--all
, --database
and
--exclude-database
. They also include
--relation
, --exclude-relation
,
--table
, --exclude-table
,
--index
, and --exclude-index
,
but only when such options are used with a three-part pattern
(e.g. mydb*.myschema*.myrel*
). Finally, they include
--schema
and --exclude-schema
when such options are used with a two-part pattern
(e.g. mydb*.myschema*
).
dbname
can also be a
connection string.
The following command-line options control what is checked:
-a
--all
Check all databases, except for any excluded via
--exclude-database
.
-d pattern
--database=pattern
Check databases matching the specified
pattern
,
except for any excluded by --exclude-database
.
This option can be specified more than once.
-D pattern
--exclude-database=pattern
Exclude databases matching the given
pattern
.
This option can be specified more than once.
-i pattern
--index=pattern
Check indexes matching the specified
pattern
,
unless they are otherwise excluded.
This option can be specified more than once.
This is similar to the --relation
option, except that
it applies only to indexes, not to other relation types.
-I pattern
--exclude-index=pattern
Exclude indexes matching the specified
pattern
.
This option can be specified more than once.
This is similar to the --exclude-relation
option,
except that it applies only to indexes, not other relation types.
-r pattern
--relation=pattern
Check relations matching the specified
pattern
,
unless they are otherwise excluded.
This option can be specified more than once.
Patterns may be unqualified, e.g. myrel*
, or they
may be schema-qualified, e.g. myschema*.myrel*
or
database-qualified and schema-qualified, e.g.
mydb*.myschema*.myrel*
. A database-qualified
pattern will add matching databases to the list of databases to be
checked.
-R pattern
--exclude-relation=pattern
Exclude relations matching the specified
pattern
.
This option can be specified more than once.
As with --relation
, the
pattern
may be unqualified, schema-qualified,
or database- and schema-qualified.
-s pattern
--schema=pattern
Check tables and indexes in schemas matching the specified
pattern
, unless they are otherwise excluded.
This option can be specified more than once.
To select only tables in schemas matching a particular pattern,
consider using something like
--table=SCHEMAPAT.* --no-dependent-indexes
.
To select only indexes, consider using something like
--index=SCHEMAPAT.*
.
A schema pattern may be database-qualified. For example, you may
write --schema=mydb*.myschema*
to select
schemas matching myschema*
in databases matching
mydb*
.
-S pattern
--exclude-schema=pattern
Exclude tables and indexes in schemas matching the specified
pattern
.
This option can be specified more than once.
As with --schema
, the pattern may be
database-qualified.
-t pattern
--table=pattern
Check tables matching the specified
pattern
,
unless they are otherwise excluded.
This option can be specified more than once.
This is similar to the --relation
option, except that
it applies only to tables, materialized views, and sequences, not to
indexes.
-T pattern
--exclude-table=pattern
Exclude tables matching the specified
pattern
.
This option can be specified more than once.
This is similar to the --exclude-relation
option,
except that it applies only to tables, materialized views, and
sequences, not to indexes.
--no-dependent-indexes
By default, if a table is checked, any btree indexes of that table
will also be checked, even if they are not explicitly selected by
an option such as --index
or
--relation
. This option suppresses that behavior.
--no-dependent-toast
By default, if a table is checked, its toast table, if any, will also
be checked, even if it is not explicitly selected by an option
such as --table
or --relation
.
This option suppresses that behavior.
--no-strict-names
By default, if an argument to --database
,
--table
, --index
,
or --relation
matches no objects, it is a fatal
error. This option downgrades that error to a warning.
The following command-line options control checking of tables:
--exclude-toast-pointers
By default, whenever a toast pointer is encountered in a table, a lookup is performed to ensure that it references apparently-valid entries in the toast table. These checks can be quite slow, and this option can be used to skip them.
--on-error-stop
After reporting all corruptions on the first page of a table where corruption is found, stop processing that table relation and move on to the next table or index.
Note that index checking always stops after the first corrupt page. This option only has meaning relative to table relations.
--skip=option
If all-frozen
is given, table corruption checks
will skip over pages in all tables that are marked as all frozen.
If all-visible
is given, table corruption checks
will skip over pages in all tables that are marked as all visible.
By default, no pages are skipped. This can be specified as
none
, but since this is the default, it need not be
mentioned.
--startblock=block
Start checking at the specified block number. An error will occur if
the table relation being checked has fewer than this number of blocks.
This option does not apply to indexes, and is probably only useful
when checking a single table relation. See --endblock
for further caveats.
--endblock=block
End checking at the specified block number. An error will occur if the
table relation being checked has fewer than this number of blocks.
This option does not apply to indexes, and is probably only useful when
checking a single table relation. If both a regular table and a toast
table are checked, this option will apply to both, but higher-numbered
toast blocks may still be accessed while validating toast pointers,
unless that is suppressed using
--exclude-toast-pointers
.
The following command-line options control checking of B-tree indexes:
--heapallindexed
For each index checked, verify the presence of all heap tuples as index
tuples in the index using amcheck's
heapallindexed
option.
--parent-check
For each btree index checked, use amcheck's
bt_index_parent_check
function, which performs
additional checks of parent/child relationships during index checking.
The default is to use amcheck's
bt_index_check
function, but note that use of the
--rootdescend
option implicitly selects
bt_index_parent_check
.
--rootdescend
For each index checked, re-find tuples on the leaf level by performing a
new search from the root page for each tuple using
amcheck's rootdescend
option.
Use of this option implicitly also selects the
--parent-check
option.
This form of verification was originally written to help in the development of btree index features. It may be of limited use or even of no use in helping detect the kinds of corruption that occur in practice. It may also cause corruption checking to take considerably longer and consume considerably more resources on the server.
The extra checks performed against B-tree indexes when the
--parent-check
option or the
--rootdescend
option is specified require
relatively strong relation-level locks. These checks are the only
checks that will block concurrent data modification from
INSERT
, UPDATE
, and
DELETE
commands.
The following command-line options control the connection to the server:
-h hostname
--host=hostname
Specifies the host name of the machine on which the server is running. If the value begins with a slash, it is used as the directory for the Unix domain socket.
-p port
--port=port
Specifies the TCP port or local Unix domain socket file extension on which the server is listening for connections.
-U
--username=username
User name to connect as.
-w
--no-password
Never issue a password prompt. If the server requires password
authentication and a password is not available by other means such as
a .pgpass
file, the connection attempt will fail.
This option can be useful in batch jobs and scripts where no user is
present to enter a password.
-W
--password
Force pg_amcheck to prompt for a password before connecting to a database.
This option is never essential, since
pg_amcheck will automatically prompt for a
password if the server demands password authentication. However,
pg_amcheck will waste a connection attempt
finding out that the server wants a password. In some cases it is
worth typing -W
to avoid the extra connection attempt.
--maintenance-db=dbname
Specifies a database or
connection string to be
used to discover the list of databases to be checked. If neither
--all
nor any option including a database pattern is
used, no such connection is required and this option does nothing.
Otherwise, any connection string parameters other than
the database name which are included in the value for this option
will also be used when connecting to the databases
being checked. If this option is omitted, the default is
postgres
or, if that fails,
template1
.
Other options are also available:
-e
--echo
Echo to stdout all SQL sent to the server.
-j num
--jobs=num
Use num
concurrent connections to the server,
or one per object to be checked, whichever is less.
The default is to use a single connection.
-P
--progress
Show progress information. Progress information includes the number of relations for which checking has been completed, and the total size of those relations. It also includes the total number of relations that will eventually be checked, and the estimated size of those relations.
-v
--verbose
Print more messages. In particular, this will print a message for each relation being checked, and will increase the level of detail shown for server errors.
-V
--version
Print the pg_amcheck version and exit.
--install-missing
--install-missing=schema
Install any missing extensions that are required to check the
database(s). If not yet installed, each extension's objects will be
installed into the given
schema
, or if not specified
into schema pg_catalog
.
At present, the only required extension is amcheck.
-?
--help
Show help about pg_amcheck command line arguments, and exit.
pg_amcheck is designed to work with PostgreSQL 14.0 and later.