OPTIMIZE

Rewrite data files to an optimal size, combining small files or splitting large files. For more information about optimizing tables, see Optimizing Tables. Users who have been assigned the ADMIN role, the table's owner, and users with SELECT and UPDATE privileges on the table can use the OPTIMIZE command.

Syntax

OPTIMIZE TABLE <table_name> 
   [ REWRITE DATA USING BIN_PACK
      [ ( { TARGET_FILE_SIZE_MB | MIN_FILE_SIZE_MB | MAX_FILE_SIZE_MB | MIN_INPUT_FILES } = <value> [, ... ] ) ]
   ]

Parameters

<table_name> String

The path of the Iceberg table that you want to optimize.

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REWRITE DATA [ USING BIN_PACK ] Optional

Either compacts smaller files or splits larger ones to the optimal file size using the bin_pack strategy. This parameter is used by default to optimize a table, but you can optionally include this parameter in your query to specify additional options to check the file sizes in your selected table. Additionally, since optimization uses only the bin_pack strategy, including the USING BIN_PACK clause is optional.

note

Dremio also optimizes Iceberg v2 tables containing position delete files.

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[ ( { TARGET_FILE_SIZE_MB | MIN_FILE_SIZE_MB | MAX_FILE_SIZE_MB | MIN_INPUT_FILES } = <value> [, ... ] ) ] Number   Optional

The options available for the REWRITE DATA USING BIN_PACK clause.

See the following table for the options that are supported.

Option Name	Default Value	Description
TARGET_FILE_SIZE_MB	256 MB	Controls the target size of the files that are generated.
MIN_FILE_SIZE_MB	0.75 times the value of TARGET_FILE_SIZE_MB	Files that are smaller in size than min_file_size_mb qualifies for compaction.
MAX_FILE_SIZE_MB	1.8 times the value of TARGET_FILE_SIZE_MB	Files that are larger in size than max_file_size_mb qualifies for compaction.
MIN_INPUT_FILES	5	The minimum number of qualified files needed to be considered for compaction.

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FOR PARTITIONS <predicate> Optional

The filter condition for partitions. This clause can only be used with data files. The predicate can be any combination of logical and mathematical conditions. For example column_1=1 selects all files where column_1 contains the number 1. Another example, column_2 like 'a%' selects all files where column_2 starts with the letter a.

note

If the specified column is not partitioned, the query will not run and an error message will display.

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REWRITE MANIFESTS Optional

Rewrites the Iceberg manifest based on a size criteria. The default target size for manifest files is 8 MB.

Examples

Rewriting the data files in the specified table to Dremio's optimal supported file size

OPTIMIZE TABLE demo.example_table

Rewriting the data files in the specified table using the default bin-packing rewrite algorithm to Dremio's optimal supported file size

OPTIMIZE TABLE demo.example_table 
   REWRITE DATA USING BIN_PACK

Rewriting the data files in the specified table to Dremio's optimal supported file size

OPTIMIZE TABLE demo.example_table 
   REWRITE DATA USING BIN_PACK (TARGET_FILE_SIZE_MB=256)

Rewriting the data files in the specified table using the specified minimum and maximum file sizes to Dremio's optimal supported file size

OPTIMIZE TABLE demo.example_table 
   REWRITE DATA USING BIN_PACK (MIN_FILE_SIZE_MB=100, MAX_FILE_SIZE_MB=1000)

Rewriting the data files in the specified table for the minimum number of specified files to Dremio's optimal supported file size

OPTIMIZE TABLE demo.example_table 
   REWRITE DATA USING BIN_PACK (MIN_INPUT_FILES=10)

Rewriting the data files in the specified table using the specified minimum and maximum file sizes to the specified target file size

OPTIMIZE TABLE demo.example_table 
   REWRITE DATA USING BIN_PACK (MIN_FILE_SIZE_MB=100, MAX_FILE_SIZE_MB=1000, TARGET_FILE_SIZE_MB=512)