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 )
OPTIONSclause withstorageLevelkey and value pair. A Warning is issued when a key other thanstorageLevelis used. The valid options forstorageLevelare:NONEDISK_ONLYDISK_ONLY_2MEMORY_ONLYMEMORY_ONLY_2MEMORY_ONLY_SERMEMORY_ONLY_SER_2MEMORY_AND_DISKMEMORY_AND_DISK_2MEMORY_AND_DISK_SERMEMORY_AND_DISK_SER_2OFF_HEAP
An Exception is thrown when an invalid value is set for
storageLevel. IfstorageLevelis not explicitly set usingOPTIONSclause, the defaultstorageLevelis set toMEMORY_AND_DISK. -
query
A query that produces the rows to be cached. It can be in one of following formats:
- a
SELECTstatement - a
TABLEstatement - a
FROMstatement
- a
Examples
CACHE TABLE testCache OPTIONS ('storageLevel' 'DISK_ONLY') SELECT * FROM testData;