[SPARK-2784][SQL] Deprecate hql() method in favor of a config option, 'spark.sql.dialect'

Many users have reported being confused by the distinction between the `sql` and `hql` methods.  Specifically, many users think that `sql(...)` cannot be used to read hive tables.  In this PR I introduce a new configuration option `spark.sql.dialect` that picks which dialect with be used for parsing.  For SQLContext this must be set to `sql`.  In `HiveContext` it defaults to `hiveql` but can also be set to `sql`.

The `hql` and `hiveql` methods continue to act the same but are now marked as deprecated.

**This is a possibly breaking change for some users unless they set the dialect manually, though this is unlikely.**

For example: `hiveContex.sql("SELECT 1")` will now throw a parsing exception by default.

Author: Michael Armbrust <michael@databricks.com>

Closes #1746 from marmbrus/sqlLanguageConf and squashes the following commits:

ad375cc [Michael Armbrust] Merge remote-tracking branch 'apache/master' into sqlLanguageConf
20c43f8 [Michael Armbrust] override function instead of just setting the value
7e4ae93 [Michael Armbrust] Deprecate hql() method in favor of a config option, 'spark.sql.dialect'

1 files changed, 4 insertions, 4 deletions

diff --git a/dev/audit-release/sbt_app_hive/src/main/scala/HiveApp.scala b/dev/audit-release/sbt_app_hive/src/main/scala/HiveApp.scala
index a21410f3b9..5111bc0adb 100644
--- a/dev/audit-release/sbt_app_hive/src/main/scala/HiveApp.scala
+++ b/dev/audit-release/sbt_app_hive/src/main/scala/HiveApp.scala
@@ -37,10 +37,10 @@ object SparkSqlExample {
     val hiveContext = new HiveContext(sc)
 
     import hiveContext._
-    hql("DROP TABLE IF EXISTS src")
-    hql("CREATE TABLE IF NOT EXISTS src (key INT, value STRING)")
-    hql("LOAD DATA LOCAL INPATH 'data.txt' INTO TABLE src")
-    val results = hql("FROM src SELECT key, value WHERE key >= 0 AND KEY < 5").collect()
+    sql("DROP TABLE IF EXISTS src")
+    sql("CREATE TABLE IF NOT EXISTS src (key INT, value STRING)")
+    sql("LOAD DATA LOCAL INPATH 'data.txt' INTO TABLE src")
+    val results = sql("FROM src SELECT key, value WHERE key >= 0 AND KEY < 5").collect()
     results.foreach(println)
     
     def test(f: => Boolean, failureMsg: String) = {