[SPARK-16199][SQL] Add a method to list the referenced columns in data source Filter

## What changes were proposed in this pull request?
It would be useful to support listing the columns that are referenced by a filter. This can help simplify data source planning, because with this we would be able to implement unhandledFilters method in HadoopFsRelation.

This is based on rxin's patch (#13901) and adds unit tests.

## How was this patch tested?
Added a new suite FiltersSuite.

Author: petermaxlee <petermaxlee@gmail.com>
Author: Reynold Xin <rxin@databricks.com>

Closes #14120 from petermaxlee/SPARK-16199.

1 files changed, 89 insertions, 0 deletions

diff --git a/sql/core/src/test/scala/org/apache/spark/sql/sources/FiltersSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/sources/FiltersSuite.scala
new file mode 100644
index 0000000000..1cb7a2156c
--- /dev/null
+++ b/sql/core/src/test/scala/org/apache/spark/sql/sources/FiltersSuite.scala
@@ -0,0 +1,89 @@
+/*
+ * 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.sources
+
+import org.apache.spark.SparkFunSuite
+
+/**
+ * Unit test suites for data source filters.
+ */
+class FiltersSuite extends SparkFunSuite {
+
+  test("EqualTo references") {
+    assert(EqualTo("a", "1").references.toSeq == Seq("a"))
+    assert(EqualTo("a", EqualTo("b", "2")).references.toSeq == Seq("a", "b"))
+  }
+
+  test("EqualNullSafe references") {
+    assert(EqualNullSafe("a", "1").references.toSeq == Seq("a"))
+    assert(EqualNullSafe("a", EqualTo("b", "2")).references.toSeq == Seq("a", "b"))
+  }
+
+  test("GreaterThan references") {
+    assert(GreaterThan("a", "1").references.toSeq == Seq("a"))
+    assert(GreaterThan("a", EqualTo("b", "2")).references.toSeq == Seq("a", "b"))
+  }
+
+  test("GreaterThanOrEqual references") {
+    assert(GreaterThanOrEqual("a", "1").references.toSeq == Seq("a"))
+    assert(GreaterThanOrEqual("a", EqualTo("b", "2")).references.toSeq == Seq("a", "b"))
+  }
+
+  test("LessThan references") {
+    assert(LessThan("a", "1").references.toSeq == Seq("a"))
+    assert(LessThan("a", EqualTo("b", "2")).references.toSeq == Seq("a", "b"))
+  }
+
+  test("LessThanOrEqual references") {
+    assert(LessThanOrEqual("a", "1").references.toSeq == Seq("a"))
+    assert(LessThanOrEqual("a", EqualTo("b", "2")).references.toSeq == Seq("a", "b"))
+  }
+
+  test("In references") {
+    assert(In("a", Array("1")).references.toSeq == Seq("a"))
+    assert(In("a", Array("1", EqualTo("b", "2"))).references.toSeq == Seq("a", "b"))
+  }
+
+  test("IsNull references") {
+    assert(IsNull("a").references.toSeq == Seq("a"))
+  }
+
+  test("IsNotNull references") {
+    assert(IsNotNull("a").references.toSeq == Seq("a"))
+  }
+
+  test("And references") {
+    assert(And(EqualTo("a", "1"), EqualTo("b", "1")).references.toSeq == Seq("a", "b"))
+  }
+
+  test("Or references") {
+    assert(Or(EqualTo("a", "1"), EqualTo("b", "1")).references.toSeq == Seq("a", "b"))
+  }
+
+  test("StringStartsWith references") {
+    assert(StringStartsWith("a", "str").references.toSeq == Seq("a"))
+  }
+
+  test("StringEndsWith references") {
+    assert(StringEndsWith("a", "str").references.toSeq == Seq("a"))
+  }
+
+  test("StringContains references") {
+    assert(StringContains("a", "str").references.toSeq == Seq("a"))
+  }
+}