feat: Use CometPlugin as main entrypoint

docs/source/contributor-guide/benchmarking.md

@@ -60,7 +60,7 @@ $SPARK_HOME/bin/spark-submit \
     --jars $COMET_JAR \
     --conf spark.driver.extraClassPath=$COMET_JAR \
     --conf spark.executor.extraClassPath=$COMET_JAR \
-    --conf spark.sql.extensions=org.apache.comet.CometSparkSessionExtensions \
+    --conf spark.plugins=org.apache.spark.CometPlugin \
     --conf spark.comet.enabled=true \
     --conf spark.comet.exec.enabled=true \
     --conf spark.comet.cast.allowIncompatible=true \

docs/source/contributor-guide/debugging.md

@@ -130,7 +130,7 @@ Then build the Comet as [described](https://github.com/apache/arrow-datafusion-c
 Start Comet with `RUST_BACKTRACE=1`
 
 ```console
-RUST_BACKTRACE=1 $SPARK_HOME/spark-shell --jars spark/target/comet-spark-spark3.4_2.12-0.1.0-SNAPSHOT.jar --conf spark.sql.extensions=org.apache.comet.CometSparkSessionExtensions --conf spark.comet.enabled=true --conf spark.comet.exec.enabled=true
+RUST_BACKTRACE=1 $SPARK_HOME/spark-shell --jars spark/target/comet-spark-spark3.4_2.12-0.1.0-SNAPSHOT.jar --conf spark.plugins=org.apache.spark.CometPlugin --conf spark.comet.enabled=true --conf spark.comet.exec.enabled=true
 ```
 
 Get the expanded exception details

docs/source/contributor-guide/plugin_overview.md

@@ -19,10 +19,10 @@ under the License.
 
 # Comet Plugin Overview
 
-The entry point to Comet is the `org.apache.comet.CometSparkSessionExtensions` class, which can be registered with Spark by adding the following setting to the Spark configuration when launching `spark-shell` or `spark-submit`:
+The entry point to Comet is the `org.apache.spark.CometPlugin` class, which can be registered with Spark by adding the following setting to the Spark configuration when launching `spark-shell` or `spark-submit`:
 
 ```
---conf spark.sql.extensions=org.apache.comet.CometSparkSessionExtensions
+--conf spark.plugins=org.apache.spark.CometPlugin
 ```
 
 On initialization, this class registers two physical plan optimization rules with Spark: `CometScanRule` and `CometExecRule`. These rules run whenever a query stage is being planned.

docs/source/user-guide/installation.md

@@ -85,7 +85,7 @@ $SPARK_HOME/bin/spark-shell \
     --jars $COMET_JAR \
     --conf spark.driver.extraClassPath=$COMET_JAR \
     --conf spark.executor.extraClassPath=$COMET_JAR \
-    --conf spark.sql.extensions=org.apache.comet.CometSparkSessionExtensions \
+    --conf spark.plugins=org.apache.spark.CometPlugin \
     --conf spark.comet.enabled=true \
     --conf spark.comet.exec.enabled=true \
     --conf spark.comet.explainFallback.enabled=true

fuzz-testing/README.md

@@ -86,7 +86,7 @@ Note that the output filename is currently hard-coded as `queries.sql`
 ```shell
 $SPARK_HOME/bin/spark-submit \
     --master $SPARK_MASTER \
-    --conf spark.sql.extensions=org.apache.comet.CometSparkSessionExtensions \
+    --conf spark.plugins=org.apache.spark.CometPlugin \
     --conf spark.comet.enabled=true \
     --conf spark.comet.exec.enabled=true \
     --conf spark.comet.exec.all.enabled=true \

spark/src/main/scala/org/apache/spark/Plugins.scala

@@ -26,6 +26,7 @@ import org.apache.spark.api.plugin.{DriverPlugin, ExecutorPlugin, PluginContext,
 import org.apache.spark.comet.shims.ShimCometDriverPlugin
 import org.apache.spark.internal.Logging
 import org.apache.spark.internal.config.{EXECUTOR_MEMORY, EXECUTOR_MEMORY_OVERHEAD}
+import org.apache.spark.sql.internal.StaticSQLConf
 
 import org.apache.comet.{CometConf, CometSparkSessionExtensions}
 
@@ -44,6 +45,9 @@ class CometDriverPlugin extends DriverPlugin with Logging with ShimCometDriverPl
   override def init(sc: SparkContext, pluginContext: PluginContext): ju.Map[String, String] = {
     logInfo("CometDriverPlugin init")
 
+    // register CometSparkSessionExtensions if it isn't already registered
+    CometDriverPlugin.registerCometSessionExtension(sc.conf)
+
     if (shouldOverrideMemoryConf(sc.getConf)) {
       val execMemOverhead = if (sc.getConf.contains(EXECUTOR_MEMORY_OVERHEAD.key)) {
         sc.getConf.getSizeAsMb(EXECUTOR_MEMORY_OVERHEAD.key)
@@ -94,6 +98,25 @@ class CometDriverPlugin extends DriverPlugin with Logging with ShimCometDriverPl
   }
 }
 
+object CometDriverPlugin extends Logging {
+  def registerCometSessionExtension(conf: SparkConf): Unit = {
+    val extensionKey = StaticSQLConf.SPARK_SESSION_EXTENSIONS.key
+    val extensionClass = classOf[CometSparkSessionExtensions].getName
+    val extensions = conf.get(extensionKey, "")
+    if (extensions.isEmpty) {
+      logInfo(s"Setting $extensionKey=$extensionClass")
+      conf.set(extensionKey, extensionClass)
+    } else {
+      val currentExtensions = extensions.split(",").map(_.trim)
+      if (!currentExtensions.contains(extensionClass)) {
+        val newValue = s"$extensions,$extensionClass"
+        logInfo(s"Setting $extensionKey=$newValue")
+        conf.set(extensionKey, newValue)
+      }
+    }
+  }
+}
+
 /**
  * The Comet plugin for Spark. To enable this plugin, set the config "spark.plugins" to
  * `org.apache.spark.CometPlugin`

spark/src/test/scala/org/apache/spark/CometPluginsSuite.scala

@@ -20,6 +20,7 @@
 package org.apache.spark
 
 import org.apache.spark.sql.CometTestBase
+import org.apache.spark.sql.internal.StaticSQLConf
 
 class CometPluginsSuite extends CometTestBase {
   override protected def sparkConf: SparkConf = {
@@ -33,6 +34,48 @@ class CometPluginsSuite extends CometTestBase {
     conf
   }
 
+  test("Register Comet extension") {
+    // test common case where no extensions are previously registered
+    {
+      val conf = new SparkConf()
+      CometDriverPlugin.registerCometSessionExtension(conf)
+      assert(
+        "org.apache.comet.CometSparkSessionExtensions" == conf.get(
+          StaticSQLConf.SPARK_SESSION_EXTENSIONS.key))
+    }
+    // test case where Comet is already registered
+    {
+      val conf = new SparkConf()
+      conf.set(
+        StaticSQLConf.SPARK_SESSION_EXTENSIONS.key,
+        "org.apache.comet.CometSparkSessionExtensions")
+      CometDriverPlugin.registerCometSessionExtension(conf)
+      assert(
+        "org.apache.comet.CometSparkSessionExtensions" == conf.get(
+          StaticSQLConf.SPARK_SESSION_EXTENSIONS.key))
+    }
+    // test case where other extensions are already registered
+    {
+      val conf = new SparkConf()
+      conf.set(StaticSQLConf.SPARK_SESSION_EXTENSIONS.key, "foo,bar")
+      CometDriverPlugin.registerCometSessionExtension(conf)
+      assert(
+        "foo,bar,org.apache.comet.CometSparkSessionExtensions" == conf.get(
+          StaticSQLConf.SPARK_SESSION_EXTENSIONS.key))
+    }
+    // test case where other extensions, including Comet, are already registered
+    {
+      val conf = new SparkConf()
+      conf.set(
+        StaticSQLConf.SPARK_SESSION_EXTENSIONS.key,
+        "foo,bar,org.apache.comet.CometSparkSessionExtensions")
+      CometDriverPlugin.registerCometSessionExtension(conf)
+      assert(
+        "foo,bar,org.apache.comet.CometSparkSessionExtensions" == conf.get(
+          StaticSQLConf.SPARK_SESSION_EXTENSIONS.key))
+    }
+  }
+
   test("Default Comet memory overhead") {
     val execMemOverhead1 = spark.conf.get("spark.executor.memoryOverhead")
     val execMemOverhead2 = spark.sessionState.conf.getConfString("spark.executor.memoryOverhead")