From c82fe4781cd0356bcfdd25c7eadf1da624bb2228 Mon Sep 17 00:00:00 2001
From: CrazyJvm <crazyjvm@gmail.com>
Date: Fri, 1 Aug 2014 11:46:13 -0700
Subject: [PATCH] [SQL] Documentation: Explain cacheTable command

add the `cacheTable` specification

Author: CrazyJvm <crazyjvm@gmail.com>

Closes #1681 from CrazyJvm/sql-programming-guide-cache and squashes the following commits:

0a231e0 [CrazyJvm] grammar fixes
a04020e [CrazyJvm] modify title to Cached tables
18b6594 [CrazyJvm] fix format
2cbbf58 [CrazyJvm] add cacheTable guide
---
 docs/sql-programming-guide.md | 10 ++++++++++
 1 file changed, 10 insertions(+)

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.
-- 
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