pg_amcheckpg_amcheck1Applicationpg_amcheckchecks for corruption in one or more
PostgreSQL databasespg_amcheckoptiondbnameDescriptionpg_amcheck supports running
'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 table relations 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
, and
. They also include
, ,
, ,
, and ,
but only when such options are used with a three-part pattern
(e.g. ). Finally, they include
and
when such options are used with a two-part pattern
(e.g. ).
dbname can also be a
connection string.
Options
pg_amcheck accepts the following command-line arguments:
Check all databases, except for any excluded via
.
Check databases matching the specified
pattern,
except for any excluded by .
This option can be specified more than once.
Exclude databases matching the given
pattern.
This option can be specified more than once.
Echo to stdout all SQL sent to the server.
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
.
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.
For each index checked, verify the presence of all heap tuples as index
tuples in the index using 's
option.
Show help about pg_amcheck command line
arguments, and exit.
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.
Check indexes matching the specified
pattern,
unless they are otherwise excluded.
This option can be specified more than once.
This is similar to the option, except that
it applies only to indexes, not tables.
Exclude indexes matching the specified
pattern.
This option can be specified more than once.
This is similar to the option,
except that it applies only to indexes, not tables.
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.
Specifies a database or
connection string to be
used to discover the list of databases to be checked. If neither
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.
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.
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.
If this option is used with --quiet, the warning
will be supressed as well.
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.
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.
For each btree index checked, use '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
option implicitly selects
bt_index_parent_check.
Specifies the TCP port or local Unix domain socket file extension on
which the server is listening for connections.
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.
Print fewer messages, and less detail regarding any server errors.
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*.myscheam*.myrel*. A database-qualified
pattern will add matching databases to the list of databases to be
checked.
Exclude relations matching the specified
pattern.
This option can be specified more than once.
As with , the
pattern may be unqualified, schema-qualified,
or database- and schema-qualified.
For each index checked, re-find tuples on the leaf level by performing a
new search from the root page for each tuple using
's option.
Use of this option implicitly also selects the
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.
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*.
Exclude tables and indexes in schemas matching the specified
pattern.
This option can be specified more than once.
As with , the pattern may be
database-qualified.
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.
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.
Check tables matching the specified
pattern,
unless they are otherwise excluded.
This option can be specified more than once.
This is similar to the option, except that
it applies only to tables, not indexes.
Exclude tables matching the specified
pattern.
This option can be specified more than once.
This is similar to the option,
except that it applies only to tables, not indexes.
User name to connect as.
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.
Print the pg_amcheck version and exit.
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.
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 to avoid the extra connection attempt.
Notespg_amcheck is designed to work with
PostgreSQL 14.0 and later.
See Also