Push down join condition conjucnts to inner side based on inherited p…

…redicate

Add equality conjuncts to inner side based on join condition and outer side symbol equalities from inherited predicate and outer side predicate
This is needed to handle queries like:

SELECT * FROM nation LEFT OUTER JOIN region ON nation.regionkey = region.regionkey and nation.name = region.name WHERE nation.name = 'blah'

Without that region.name = 'blah' was not pushed to inner side

presto-main/src/main/java/com/facebook/presto/sql/planner/optimizations/PredicatePushDown.java

@@ -472,6 +472,13 @@ private OuterJoinPushDownResult processLimitedOuterJoin(Expression inheritedPred
                     joinConjuncts.add(conjunct);
                 }
             }
+
+            // Push outer and join equalities into the inner side. For example:
+            // SELECT * FROM nation LEFT OUTER JOIN region ON nation.regionkey = region.regionkey and nation.name = region.name WHERE nation.name = 'blah'
+
+            EqualityInference potentialNullSymbolInferenceWithoutInnerInferred = createEqualityInference(outerOnlyInheritedEqualities, outerEffectivePredicate, joinPredicate);
+            innerPushdownConjuncts.addAll(potentialNullSymbolInferenceWithoutInnerInferred.generateEqualitiesPartitionedBy(not(in(outerSymbols))).getScopeEqualities());
+
             // TODO: we can further improve simplifying the equalities by considering other relationships from the outer side
             EqualityInference.EqualityPartition joinEqualityPartition = createEqualityInference(joinPredicate).generateEqualitiesPartitionedBy(not(in(outerSymbols)));
             innerPushdownConjuncts.addAll(joinEqualityPartition.getScopeEqualities());