Avoid calling statistics on plans if auto join conversion is disabled.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala

@@ -28,9 +28,9 @@ abstract class LogicalPlan extends QueryPlan[LogicalPlan] {
 
   // TODO: handle overflow?
   /**
-   * Estimates of various statistics.  The default estimation logic simply sums up the corresponding
-   * statistic produced by the children.  To override this behavior, override `statistics` and
-   * assign it a overriden version of `Statistics`.
+   * Estimates of various statistics.  The default estimation logic simply lazily multiplies the
+   * corresponding statistic produced by the children.  To override this behavior, override
+   * `statistics` and assign it an overriden version of `Statistics`.
    *
    * '''NOTE''': concrete and/or overriden versions of statistics fields should pay attention to the
    * performance of the implementations.  The reason is that estimations might get triggered in

sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala

@@ -58,7 +58,7 @@ private[sql] abstract class SparkStrategies extends QueryPlanner[SparkPlan] {
    * side in a [[execution.ShuffledHashJoin]].
    */
   object HashJoin extends Strategy with PredicateHelper {
-    private[this] def broadcastHashJoin(
+    private[this] def makeBroadcastHashJoin(
         leftKeys: Seq[Expression],
         rightKeys: Seq[Expression],
         left: LogicalPlan,
@@ -72,12 +72,14 @@ private[sql] abstract class SparkStrategies extends QueryPlanner[SparkPlan] {
 
     def apply(plan: LogicalPlan): Seq[SparkPlan] = plan match {
       case ExtractEquiJoinKeys(Inner, leftKeys, rightKeys, condition, left, right)
-        if right.statistics.sizeInBytes <= sqlContext.autoConvertJoinSize =>
-          broadcastHashJoin(leftKeys, rightKeys, left, right, condition, BuildRight)
+        if sqlContext.autoConvertJoinSize > 0 &&
+          right.statistics.sizeInBytes <= sqlContext.autoConvertJoinSize =>
+          makeBroadcastHashJoin(leftKeys, rightKeys, left, right, condition, BuildRight)
 
       case ExtractEquiJoinKeys(Inner, leftKeys, rightKeys, condition, left, right)
-        if left.statistics.sizeInBytes <= sqlContext.autoConvertJoinSize =>
-          broadcastHashJoin(leftKeys, rightKeys, left, right, condition, BuildLeft)
+        if sqlContext.autoConvertJoinSize > 0 &&
+          left.statistics.sizeInBytes <= sqlContext.autoConvertJoinSize =>
+          makeBroadcastHashJoin(leftKeys, rightKeys, left, right, condition, BuildLeft)
 
       case ExtractEquiJoinKeys(Inner, leftKeys, rightKeys, condition, left, right) =>
         val buildSide =