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| -rw-r--r-- | docs/sql-programming-guide.md | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/docs/sql-programming-guide.md b/docs/sql-programming-guide.md index a047d32b6e..7261badd41 100644 --- a/docs/sql-programming-guide.md +++ b/docs/sql-programming-guide.md @@ -769,3 +769,13 @@ To start the Spark SQL CLI, run the following in the Spark directory: Configuration of Hive is done by placing your `hive-site.xml` file in `conf/`. You may run `./bin/spark-sql --help` for a complete list of all available options. + +# Cached tables + +Spark SQL can cache tables using an in-memory columnar format by calling `cacheTable("tableName")`. +Then Spark SQL will scan only required columns and will automatically tune compression to minimize +memory usage and GC pressure. You can call `uncacheTable("tableName")` to remove the table from memory. + +Note that if you just call `cache` rather than `cacheTable`, tables will _not_ be cached in +in-memory columnar format. So we strongly recommend using `cacheTable` whenever you want to +cache tables. |