clusterdb

Reclusters tables that were previously clustered with CLUSTER.

Synopsis

clusterdb [<connection-option> ...] [--verbose | -v] [--table | -t <table>] [[--dbname | -d] <dbname]

clusterdb [<connection-option> ...] [--verbose | -v] --all | -a

clusterdb -? | --help

clusterdb -V | --version

Description

To cluster a table means to physically reorder a table on disk according to an index. Clustering helps improving index seek performance for queries that use that index. Clustering is a one-time operation: when the table is subsequently updated, the changes are not clustered. That is, no attempt is made to store new or updated rows according to their index order.

The clusterdb utility will find any tables in a database that have previously been clustered with the CLUSTER SQL command, and clusters them again on the same index that was last used. Tables that have never been clustered are not affected.

clusterdb is a wrapper around the SQL command CLUSTER. There is no effective difference between clustering databases via this utility and via other methods for accessing the server.

Options

clusterdb accepts the following command-line arguments:

-a --all Cluster all databases.

[-d] dbname [--dbname=]dbname Specifies the name of the database to be clustered, when -a/--all is not used. If this is not specified, the database name is read from the environment variable PGDATABASE. If that is not set, the user name specified for the connection is used. The dbname can be a connection string. If so, connection string parameters will override any conflicting command line options.

-e --echo Echo the commands that clusterdb generates and sends to the server.

-q --quiet Do not display progress messages.

-t table --table=table Cluster the named table only. You can cluster multiple tables by specifying multiple -t switches.

-v --verbose Print detailed information during processing.

-V --version Print the clusterdb version, and exit.

-? --help Show help about clusterdb command line arguments, and exit.

Connection Options

clusterdb also accepts the following command-line arguments for connection parameters:

-h host --host=host Specifies the host name of the machine on which the WarehousePG coordinator database server is running. If not specified, reads from the environment variable PGHOST or defaults to localhost.

-p port --port=port Specifies the TCP port on which the WarehousePG coordinator database server is listening for connections. If not specified, reads from the environment variable PGPORT or defaults to 5432.

-U username --username=username The database role name to connect as. If not specified, reads from the environment variable PGUSER or defaults to the current system role name.

-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 clusterdb to prompt for a password before connecting to a database. This option is never essential, since clusterdb will automatically prompt for a password if the server demands password authentication. However, clusterdb 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 the name of the database to connect to discover what other databases should be clustered. If not specified, the postgres database will be used, and if that does not exist, template1 will be used. This can be a connection string. If so, connection string parameters will override any conflicting command line options. Also, connection string parameters other than the database name itself will be re-used when connecting to other databases.

Environment

PGDATABASE PGHOST PGPORT PGUSER Default connection parameters.

PG_COLOR Specifies whether to use color in diagnostic messages. Possible values are always, auto, and never.

This utility, like most other WarehousePG utilities, also uses the environment variables supported by libpq.

Diagnostics

In case of difficulty, see CLUSTER and psql for discussions of potential problems and error messages. The database server must be running at the targeted host. Also, any default connection settings and environment variables used by the libpq front-end library will apply.

Examples

To cluster the database named test:

clusterdb test

To cluster a single table foo in a database named xyzzy:

clusterdb --table=foo xyzzy

See Also

CLUSTER