3.3

OPTIMIZE

Optimize one or more tables explicitly.

Table of Contents

Synopsis

OPTIMIZE TABLE (table_ident [ PARTITION (partition_column=value [ , ... ])] [, ...] )
[ WITH ( optimization_parameter [= value] [, ... ] ) ]

Description

The OPTIMIZE TABLE command optimizes tables and table partitions by merging the segments of a table or a partition and reducing their number. It is also used to upgrade tables and table partitions to the current version of the storage engine. This command will block until the optimization process is complete. If the connection to CrateDB is lost, the request will continue in the background, and any new requests will block until the previous optimization is complete.

The PARTITION clause can be used to only optimize specific partitions of a partitioned table. All columns by which a table is partitioned are required.

In case the PARTITION clause is omitted all open partitions will be optimized. Closed partitions are not optimized. For performance reasons doing that should be avoided if possible.

See Partitioned Tables for more information on partitioned tables.

For further information see Optimization.

Note

System tables cannot be optimized

Parameters

table_ident

The name (optionally schema-qualified) of an existing table that is to be optimized.

partition_column

Column name by which the table is partitioned.

Clauses

PARTITION

[ PARTITION ( partition_column = value [ , ... ] ) ]
partition_column

The name of the column by which the table is partitioned.

All partition columns that were part of the PARTITIONED BY of the CREATE TABLE statement must be specified.

value

The columns value.

WITH

The optional WITH clause can specify parameters for the optimization request.

[ WITH ( optimization_parameter [= value] [, ... ] ) ]
optimization_parameter

Specifies an optional parameter for the optimization request.

Available parameters are:

max_num_segments

The number of segments to merge to. To fully merge the table or partition set it to 1.

Defaults to simply checking if a merge is necessary, and if so, executes it.

only_expunge_deletes

Should the merge process only expunge segments with deletes in it.

In CrateDB, a row is not deleted from a segment, just marked as deleted. During a merge process of segments, a new segment is created that does not have those deletes. This flag allows to only merge segments that have deletes.

Defaults to false.

flush

Instructs if a flush should be performed after the optimization.

Defaults to true.

upgrade_segments

Don’t optimize but instead upgrade all segments of the table/partition to the current version of storage engine.

Defaults to false.

Note

upgrade_segments cannot be used in combination with other parameters