[SPARK-30876][SQL] Optimizer fails to infer constraints within join

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

@@ -116,7 +116,8 @@ abstract class Optimizer(catalogManager: CatalogManager)
         operatorOptimizationRuleSet.filterNot(_ == InferFiltersFromConstraints)
       Batch("Operator Optimization before Inferring Filters", fixedPoint,
         rulesWithoutInferFiltersFromConstraints: _*) ::
-      Batch("Infer Filters", Once,
+      Batch("Infer Filters", fixedPoint,
+        PushDownPredicates,
         InferFiltersFromConstraints) ::
       Batch("Operator Optimization after Inferring Filters", fixedPoint,
         rulesWithoutInferFiltersFromConstraints: _*) ::

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

@@ -0,0 +1,63 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.catalyst.optimizer
+
+import org.apache.spark.sql.catalyst.dsl.expressions._
+import org.apache.spark.sql.catalyst.dsl.plans._
+import org.apache.spark.sql.catalyst.expressions.{IsNotNull, Literal}
+import org.apache.spark.sql.catalyst.expressions.aggregate.Count
+import org.apache.spark.sql.catalyst.plans.{Inner, PlanTest}
+import org.apache.spark.sql.catalyst.plans.logical.{LocalRelation, LogicalPlan}
+import org.apache.spark.sql.catalyst.rules.RuleExecutor
+
+class InferFiltersPredicatePushdownSuite extends PlanTest {
+
+  object Optimize extends RuleExecutor[LogicalPlan] {
+    val b = Batch("InferAndPushDownFilters", FixedPoint(100),
+      PushPredicateThroughJoin,
+      ColumnPruning
+    )
+    val batches =
+      b ::
+      Batch("infer filter from constraints", FixedPoint(100),
+        PushDownPredicates,
+        InferFiltersFromConstraints) ::
+        Nil
+  }
+  val  testRelation = LocalRelation('a.int, 'b.int, 'c.int)
+
+  test("SPARK-30876: optimize constraints in 3-way join") {
+    val x = testRelation.subquery('x)
+    val y = testRelation.subquery('y)
+    val z = testRelation.subquery('z)
+    val originalQuery = x.join(y).join(z)
+      .where(("x.a".attr === "y.b".attr) && ("y.b".attr === "z.c".attr) && ("z.c".attr === 1))
+      .groupBy()(Count(Literal("*"))).analyze
+    val optimized = Optimize.execute(originalQuery)
+    val correctAnswer = x.where('a === 1 && IsNotNull('a)).select('a)
+      .join(y.where('b === 1 && IsNotNull('b))
+        .select('b), Inner, Some("x.a".attr === "y.b".attr))
+      .select('b)
+      .join(z.where('c === 1 && IsNotNull('c))
+        .select('c), Inner, Some('b === "z.c".attr))
+      .select()
+      .groupBy()(Count(Literal("*"))).analyze
+    comparePlans(optimized, correctAnswer)
+  }
+
+}