Change default native memory management method to greedy_task_shared

Author: Kontinuation

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

@@ -436,9 +436,9 @@ object CometConf extends ShimCometConf {
       "The type of memory pool to be used for Comet native execution. " +
         "Available memory pool types are 'greedy', 'fair_spill', 'greedy_task_shared', " +
         "'fair_spill_task_shared', 'greedy_global' and 'fair_spill_global', By default, " +
-        "this config is 'greedy'.")
+        "this config is 'greedy_task_shared'.")
     .stringConf
-    .createWithDefault("greedy")
+    .createWithDefault("greedy_task_shared")
 
   val COMET_PARQUET_ENABLE_DIRECT_BUFFER: ConfigEntry[Boolean] = conf(
     "spark.comet.parquet.enable.directBuffer")

docs/source/user-guide/configs.md

@@ -49,7 +49,7 @@ Comet provides the following configuration settings.
 | spark.comet.exec.hashJoin.enabled | Whether to enable hashJoin by default. | true |
 | spark.comet.exec.localLimit.enabled | Whether to enable localLimit by default. | true |
 | spark.comet.exec.memoryFraction | The fraction of memory from Comet memory overhead that the native memory manager can use for execution. The purpose of this config is to set aside memory for untracked data structures, as well as imprecise size estimation during memory acquisition. Default value is 0.7. | 0.7 |
-| spark.comet.exec.memoryPool | The type of memory pool to be used for Comet native execution. Available memory pool types are 'greedy', 'fair_spill', 'greedy_task_shared', 'fair_spill_task_shared', 'greedy_global' and 'fair_spill_global', By default, this config is 'greedy'. | greedy |
+| spark.comet.exec.memoryPool | The type of memory pool to be used for Comet native execution. Available memory pool types are 'greedy', 'fair_spill', 'greedy_task_shared', 'fair_spill_task_shared', 'greedy_global' and 'fair_spill_global', By default, this config is 'greedy_task_shared'. | greedy_task_shared |
 | spark.comet.exec.project.enabled | Whether to enable project by default. | true |
 | spark.comet.exec.shuffle.codec | The codec of Comet native shuffle used to compress shuffle data. Only zstd is supported. | zstd |
 | spark.comet.exec.shuffle.enabled | Whether to enable Comet native shuffle. Note that this requires setting 'spark.shuffle.manager' to 'org.apache.spark.sql.comet.execution.shuffle.CometShuffleManager'. 'spark.shuffle.manager' must be set before starting the Spark application and cannot be changed during the application. | true |