CHECKPOINT

force a write-ahead log checkpoint

Synopsis

CHECKPOINT [ ( option [, ...] ) ]

where OPTION can be one of:

    FLUSH_UNLOGGED [ BOOLEAN ]
    MODE { FAST | SPREAD }

Description

A checkpoint is a point in the write-ahead log sequence at which all data files for permanent relations have been updated to reflect the information in the log. All data for permanent relation files will be flushed to disk. Dirty buffers of unlogged relations are not flushed unless FLUSH_UNLOGGED is specified. Refer to WAL Configuration for more details about what happens during a checkpoint.

By default, the CHECKPOINT command forces a fast checkpoint when the command is issued, without waiting for a regular checkpoint scheduled by the system (controlled by the settings in Checkpoints). To request the checkpoint be spread over a longer interval, set the MODE option to SPREAD. CHECKPOINT is not intended for use during normal operation.

The server may consolidate concurrently requested checkpoints. Such consolidated requests will contain a combined set of options. For example, if one session requests a fast checkpoint and another requests a spread checkpoint, the server may combine those requests and perform one fast checkpoint.

If executed during recovery, the CHECKPOINT command will force a restartpoint (see WAL Configuration) rather than writing a new checkpoint.

Only superusers or users with the privileges of the pg_checkpoint role can call CHECKPOINT.

Parameters

FLUSH_UNLOGGED

Normally, CHECKPOINT does not flush dirty buffers of unlogged relations. This option, which is disabled by default, enables flushing unlogged relations to disk.

MODE

When set to FAST, which is the default, the requested checkpoint will be completed as fast as possible, which may result in a significantly higher rate of I/O during the checkpoint.

MODE can also be set to SPREAD to request the checkpoint be spread over a longer interval (controlled via the settings in Checkpoints), like a regular checkpoint scheduled by the system. This can reduce the rate of I/O during the checkpoint.

boolean

Specifies whether the selected option should be turned on or off. You can write TRUE, ON, or 1 to enable the option, and FALSE, OFF, or 0 to disable it. The boolean value can also be omitted, in which case TRUE is assumed.

Compatibility

The CHECKPOINT command is a PostgreSQL language extension.