Spark SQL Guide

CACHE TABLE

Description

CACHE TABLE statement caches contents of a table or output of a query with the given storage level. This reduces scanning of the original files in future queries.

Syntax

CACHE [ LAZY ] TABLE table_identifier
    [ OPTIONS ( 'storageLevel' [ = ] value ) ] [ [ AS ] query ]

Parameters

LAZY
Only cache the table when it is first used, instead of immediately.
table_identifier
Specifies the table or view name to be cached. The table or view name may be optionally qualified with a database name.

Syntax: [ database_name. ] table_name
OPTIONS ( 'storageLevel' [ = ] value )
OPTIONS clause with storageLevel key and value pair. A Warning is issued when a key other than storageLevel is used. The valid options for storageLevel are:
  • NONE
  • DISK_ONLY
  • DISK_ONLY_2
  • MEMORY_ONLY
  • MEMORY_ONLY_2
  • MEMORY_ONLY_SER
  • MEMORY_ONLY_SER_2
  • MEMORY_AND_DISK
  • MEMORY_AND_DISK_2
  • MEMORY_AND_DISK_SER
  • MEMORY_AND_DISK_SER_2
  • OFF_HEAP
An Exception is thrown when an invalid value is set for storageLevel. If storageLevel is not explicitly set using OPTIONS clause, the default storageLevel is set to MEMORY_AND_DISK.
query
A query that produces the rows to be cached. It can be in one of following formats:
  • a SELECT statement
  • a TABLE statement
  • a FROM statement

Examples

CACHE TABLE testCache OPTIONS ('storageLevel' 'DISK_ONLY') SELECT * FROM testData;