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. Specified values for all partition columns 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.

Clauses

PARTITION

If the table is partitioned, the optional PARTITION clause can be used to optimize one partition exclusively.

[ PARTITION ( partition_column = value [ , ... ] ) ]
partition_column:One of the column names used for table partitioning.
value:The respective column value.

All partition columns (specified by the PARTITIONED BY clause) must be listed inside the parentheses along with their respective values using the partition_column = value syntax (separated by commas).

Because each partition corresponds to a unique set of partition column row values, this clause uniquely identifies a single partition to optimize.

Tip

The SHOW CREATE TABLE statement will show you the complete list of partition columns specified by the PARTITIONED BY clause.

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

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