fix: disable initCap by default

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

@@ -189,6 +189,8 @@ object CometConf extends ShimCometConf {
     createExecEnabledConfig("window", defaultValue = true)
   val COMET_EXEC_TAKE_ORDERED_AND_PROJECT_ENABLED: ConfigEntry[Boolean] =
     createExecEnabledConfig("takeOrderedAndProject", defaultValue = true)
+  val COMET_EXEC_INITCAP_ENABLED: ConfigEntry[Boolean] =
+    createExecEnabledConfig("initCap", defaultValue = false)
 
   val COMET_EXEC_SORT_MERGE_JOIN_WITH_JOIN_FILTER_ENABLED: ConfigEntry[Boolean] =
     conf("spark.comet.exec.sortMergeJoinWithJoinFilter.enabled")

docs/source/user-guide/configs.md

@@ -46,6 +46,7 @@ Comet provides the following configuration settings.
 | spark.comet.exec.filter.enabled | Whether to enable filter by default. | true |
 | spark.comet.exec.globalLimit.enabled | Whether to enable globalLimit by default. | true |
 | spark.comet.exec.hashJoin.enabled | Whether to enable hashJoin by default. | true |
+| spark.comet.exec.initCap.enabled | Whether to enable initCap by default. | false |
 | spark.comet.exec.localLimit.enabled | Whether to enable localLimit by default. | true |
 | 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/src/main/scala/org/apache/comet/serde/QueryPlanSerde.scala

@@ -1795,10 +1795,19 @@ object QueryPlanSerde extends Logging with ShimQueryPlanSerde with CometExprShim
           optExprWithInfo(optExpr, expr, child)
 
         case InitCap(child) =>
-          val castExpr = Cast(child, StringType)
-          val childExpr = exprToProtoInternal(castExpr, inputs)
-          val optExpr = scalarExprToProto("initcap", childExpr)
-          optExprWithInfo(optExpr, expr, castExpr)
+          if (CometConf.COMET_EXEC_INITCAP_ENABLED.get()) {
+            val castExpr = Cast(child, StringType)
+            val childExpr = exprToProtoInternal(castExpr, inputs)
+            val optExpr = scalarExprToProto("initcap", childExpr)
+            optExprWithInfo(optExpr, expr, castExpr)
+          } else {
+            withInfo(
+              expr,
+              "Comet initCap is not compatible with Spark yet. " +
+                "See https://github.com/apache/datafusion-comet/issues/1052 ." +
+                s"Set ${CometConf.COMET_EXEC_INITCAP_ENABLED.key}=true to enable it anyway.")
+            None
+          }
 
         case Length(child) =>
           val castExpr = Cast(child, StringType)

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

@@ -1364,8 +1364,14 @@ class CometExpressionSuite extends CometTestBase with AdaptiveSparkPlanHelper {
           sql(s"create table $table(id int, name varchar(20)) using parquet")
           sql(
             s"insert into $table values(1, 'james smith'), (2, 'michael rose'), " +
-              "(3, 'robert williams'), (4, 'rames rose'), (5, 'james smith')")
-          checkSparkAnswerAndOperator(s"SELECT initcap(name) FROM $table")
+              "(3, 'robert williams'), (4, 'rames rose'), (5, 'james smith'), " +
+              "(6, 'robert rose-smith'), (7, 'james ähtäri')")
+          if (CometConf.COMET_EXEC_INITCAP_ENABLED.get()) {
+            // TODO: remove this if clause https://github.com/apache/datafusion-comet/issues/1052
+            checkSparkAnswerAndOperator(s"SELECT initcap(name) FROM $table")
+          } else {
+            checkSparkAnswer(s"SELECT initcap(name) FROM $table")
+          }
         }
       }
     }