[SPARK-22759][SQL] Filters can be combined iff both are deterministic

## What changes were proposed in this pull request?
The query execution/optimization does not guarantee the expressions are evaluated in order. We only can combine them if and only if both are deterministic. We need to update the optimizer rule: CombineFilters.

## How was this patch tested?
Updated the existing tests.

Author: gatorsmile <[email protected]>

Closes #19947 from gatorsmile/combineFilters.

Author: gatorsmile

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala

@@ -695,7 +695,9 @@ object CombineUnions extends Rule[LogicalPlan] {
  */
 object CombineFilters extends Rule[LogicalPlan] with PredicateHelper {
   def apply(plan: LogicalPlan): LogicalPlan = plan transform {
-    case Filter(fc, nf @ Filter(nc, grandChild)) =>
+    // The query execution/optimization does not guarantee the expressions are evaluated in order.
+    // We only can combine them if and only if both are deterministic.
+    case Filter(fc, nf @ Filter(nc, grandChild)) if fc.deterministic && nc.deterministic =>
       (ExpressionSet(splitConjunctivePredicates(fc)) --
         ExpressionSet(splitConjunctivePredicates(nc))).reduceOption(And) match {
         case Some(ac) =>

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/FilterPushdownSuite.scala

@@ -94,19 +94,15 @@ class FilterPushdownSuite extends PlanTest {
     comparePlans(optimized, correctAnswer)
   }
 
-  test("combine redundant deterministic filters") {
+  test("do not combine non-deterministic filters even if they are identical") {
     val originalQuery =
       testRelation
         .where(Rand(0) > 0.1 && 'a === 1)
-        .where(Rand(0) > 0.1 && 'a === 1)
+        .where(Rand(0) > 0.1 && 'a === 1).analyze
 
-    val optimized = Optimize.execute(originalQuery.analyze)
-    val correctAnswer =
-      testRelation
-        .where(Rand(0) > 0.1 && 'a === 1 && Rand(0) > 0.1)
-        .analyze
+    val optimized = Optimize.execute(originalQuery)
 
-    comparePlans(optimized, correctAnswer)
+    comparePlans(optimized, originalQuery)
   }
 
   test("SPARK-16164: Filter pushdown should keep the ordering in the logical plan") {