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[SPARK-4930][SQL][DOCS]Update SQL programming guide, CACHE TABLE is eager #3773

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[SPARK-4930][SQL][DOCS]Update SQL programming guide, CACHE TABLE is eager #3773

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[SPARK-4930][SQL][DOCS]Update SQL programming guide, CACHE TABLE tbl …
luogankun Dec 23, 2014
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[SPARK-4930][SQL][DOCS]Update SQL programming guide, add CACHE [LAZY]…
luogankun Dec 23, 2014
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9 changes: 4 additions & 5 deletions docs/sql-programming-guide.md
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Expand Up @@ -1010,12 +1010,11 @@ let user control table caching explicitly:
CACHE TABLE logs_last_month;
UNCACHE TABLE logs_last_month;

**NOTE:** `CACHE TABLE tbl` is lazy, similar to `.cache` on an RDD. This command only marks `tbl` to ensure that
partitions are cached when calculated but doesn't actually cache it until a query that touches `tbl` is executed.
To force the table to be cached, you may simply count the table immediately after executing `CACHE TABLE`:
**NOTE:** `CACHE TABLE tbl` is now __eager__ by default not __lazy__. Don’t need to trigger cache materialization manually anymore.

CACHE TABLE logs_last_month;
SELECT COUNT(1) FROM logs_last_month;
Spark SQL newly introduced a statement to let user control table caching whether or not lazy since Spark 1.2.0:

CACHE [LAZY] TABLE [AS SELECT] ...

Several caching related features are not supported yet:

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