chore: Disable shuffle by default and add unit test to prevent config…

… regressions (apache#414)

* Set internal default configs

* add header

* comment out shuffle mode check

* revert shuffle mode default change

* revert enable shuffle by default

* update defaults

common/src/main/scala/org/apache/comet/CometConf.scala

@@ -189,7 +189,7 @@ object CometConf extends ShimCometConf {
           "'spark.shuffle.manager' must be set before starting the Spark application and " +
           "cannot be changed during the application.")
       .booleanConf
-      .createWithDefault(true)
+      .createWithDefault(false)
 
   val COMET_SHUFFLE_MODE: ConfigEntry[String] = conf(s"$COMET_EXEC_CONFIG_PREFIX.shuffle.mode")
     .doc("The mode of Comet shuffle. This config is only effective if Comet shuffle " +

spark/src/test/scala/org/apache/comet/AppleDefaultConfigSuite.scala

@@ -0,0 +1,59 @@
+/*
+ * 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.comet
+
+import org.apache.spark.sql.CometTestBase
+
+class AppleDefaultConfigSuite extends CometTestBase {
+
+  test("Comet configuration defaults are as expected") {
+    // check that we haven't accidentally changed any defaults when we merge changes from OSS Comet
+
+    // scans should be enabled by default
+    assert(CometConf.COMET_NATIVE_SCAN_ENABLED.defaultValue.get)
+
+    // execs should be disabled by default and users can opt in to try out Comet
+    // we will enable by default once all memory and performance issues are resolved
+    assert(!CometConf.COMET_EXEC_ENABLED.defaultValue.get)
+
+    // individual execs all default to enabled
+    assert(CometConf.COMET_EXEC_AGGREGATE_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_BROADCAST_EXCHANGE_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_BROADCAST_HASH_JOIN_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_COALESCE_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_COLLECT_LIMIT_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_EXPAND_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_FILTER_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_GLOBAL_LIMIT_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_HASH_JOIN_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_LOCAL_LIMIT_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_PROJECT_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_SORT_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_SORT_MERGE_JOIN_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_TAKE_ORDERED_AND_PROJECT_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_UNION_ENABLED.defaultValue.get)
+    assert(CometConf.COMET_EXEC_WINDOW_ENABLED.defaultValue.get)
+
+    // shuffle is disabled by default
+    assert(!CometConf.COMET_EXEC_SHUFFLE_ENABLED.defaultValue.get)
+    assert("auto" == CometConf.COMET_SHUFFLE_MODE.defaultValue.get)
+  }
+
+}