DRILL-7038: Queries on partitioned columns scan the entire datasets

- Added new optimizer rule which checks if query references directory columns only and has DISTINCT or GROUP BY operation. If the condition holds, instead of scanning full file set the following will be performed:
1) if there is cache metadata file, these directories will be read from it,
2) otherwise directories will be gathered from selection object (PartitionLocation).

In the end Scan node will be transformed to DrillValuesRel (containing constant literals) with gathered values so no scan will be performed.
closes #1640

1 files changed, 73 insertions, 0 deletions

diff --git a/exec/java-exec/src/test/java/org/apache/drill/TestDirScanToValuesConversion.java b/exec/java-exec/src/test/java/org/apache/drill/TestDirScanToValuesConversion.java
new file mode 100644
index 000000000..1aeeb5ffb
--- /dev/null
+++ b/exec/java-exec/src/test/java/org/apache/drill/TestDirScanToValuesConversion.java
@@ -0,0 +1,73 @@
+/*
+ * 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.drill;
+
+import org.apache.drill.categories.PlannerTest;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+import java.nio.file.Paths;
+
+@Category({PlannerTest.class})
+public class TestDirScanToValuesConversion extends PlanTestBase {
+
+  private static final String TABLE_WITH_METADATA = "parquetTable1";
+
+  @BeforeClass
+  public static void setUp() {
+    dirTestWatcher.copyResourceToRoot(Paths.get("multilevel"));
+    dirTestWatcher.copyResourceToRoot(Paths.get("multilevel/parquet"), Paths.get(TABLE_WITH_METADATA));
+  }
+
+  @Test
+  public void testDirScanToValuesConversion() throws Exception {
+    String[] tableNames = {"multilevel/parquet", "multilevel/json", "multilevel/csv"};
+    String[] queries = {
+        "select distinct dir0, dir1 from dfs.`%s`",
+        "select dir0, dir1 from dfs.`%s` group by 1, 2"
+    };
+    for (String tableName : tableNames) {
+      for (String query : queries) {
+        testPlanMatchingPatterns(String.format(query, tableName), new String[]{"Values\\(tuples="}, new String[]{"Scan\\(table="});
+      }
+    }
+  }
+
+  @Test
+  public void testDirScanToValuesConversionWithMetadataCache() throws Exception {
+    test("refresh table metadata dfs.`%s`", TABLE_WITH_METADATA);
+    checkForMetadataFile(TABLE_WITH_METADATA);
+    String query = String.format("select distinct dir0, dir1 from dfs.`%s`", TABLE_WITH_METADATA);
+    PlanTestBase.testPlanMatchingPatterns(query, new String[]{"Values\\(tuples="}, null);
+  }
+
+  @Test
+  public void testDirScanToValuesConversionIsNotApplied() throws Exception {
+    String[] tableNames = {"multilevel/parquet", "multilevel/json", "multilevel/csv"};
+    String[] queries = {
+        "select dir0, dir1 from dfs.`%s`", // no aggregation
+        "select dir0, dir1, o_custkey from dfs.`%s` group by 1, 2, 3" // not only partition columns present
+    };
+    for (String tableName : tableNames) {
+      for (String query : queries) {
+        testPlanMatchingPatterns(String.format(query, tableName), new String[]{"Scan\\(table="}, new String[]{"Values\\(tuples="});
+      }
+    }
+  }
+}