CACHE TABLE
Description
CACHE TABLE
statement caches contents of a table or output of a query with the given storage level. If a query is cached, then a temp view will be created for this query.
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 withstorageLevel
key and value pair. A Warning is issued when a key other thanstorageLevel
is used. The valid options forstorageLevel
are:NONE
DISK_ONLY
DISK_ONLY_2
DISK_ONLY_3
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
. IfstorageLevel
is not explicitly set usingOPTIONS
clause, the defaultstorageLevel
is set toMEMORY_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
- a
Examples
CACHE TABLE testCache OPTIONS ('storageLevel' 'DISK_ONLY') SELECT * FROM testData;