[GitHub] [hudi] yihua commented on a diff in pull request #5244: [WIP][HUDI-3812] Fixing Data Skipping configuration to respect Metadata Table configs

[GitBox <gi...@apache.org>]

yihua commented on code in PR #5244:
URL: https://github.com/apache/hudi/pull/5244#discussion_r844550905


##########
hudi-common/src/main/java/org/apache/hudi/common/config/HoodieMetadataConfig.java:
##########
@@ -48,7 +48,8 @@
       .sinceVersion("0.7.0")
       .withDocumentation("Enable the internal metadata table which serves table metadata like level file listings");
 
-  public static final boolean DEFAULT_METADATA_ENABLE_FOR_READERS = false;
+  // TODO rectify
+  public static final boolean DEFAULT_METADATA_ENABLE_FOR_READERS = true;

Review Comment:
   A reminder here to remove this change before merging.



##########
hudi-spark-datasource/hudi-spark-common/src/main/scala/org/apache/hudi/HoodieFileIndex.scala:
##########
@@ -196,12 +191,20 @@ case class HoodieFileIndex(spark: SparkSession,
    * @return list of pruned (data-skipped) candidate base-files' names
    */
   private def lookupCandidateFilesInMetadataTable(queryFilters: Seq[Expression]): Try[Option[Set[String]]] = Try {
-    if (!isDataSkippingEnabled || queryFilters.isEmpty || !HoodieTableMetadataUtil.getCompletedMetadataPartitions(metaClient.getTableConfig)
-      .contains(HoodieTableMetadataUtil.PARTITION_NAME_COLUMN_STATS)) {
+    // NOTE: Data Skipping is only effective when it references columns that are indexed w/in
+    //       the Column Stats Index (CSI). Following cases could not be effectively handled by Data Skipping:
+    //          - Expressions on top-level column's fields (ie, for ex filters like "struct.field > 0", since
+    //          CSI only contains stats for top-level columns, in this case for "struct")
+    //          - Any expression not directly referencing top-level column (for ex, sub-queries, since there's
+    //          nothing CSI in particular could be applied for)
+    lazy val queryReferencedColumns = collectReferencedColumns(spark, queryFilters, schema)
+
+    if (!isMetadataTableEnabled || !isColumnStatsIndexEnabled || !isColumnStatsIndexAvailable || !isDataSkippingEnabled) {

Review Comment:
   The check here should not rely on `isMetadataTableEnabled` (`hoodie.metadata.enable`) and `isColumnStatsIndexEnabled` (`hoodie.metadata.index.column.stats.enable`) which may not be the source of truth on the query side.  `isColumnStatsIndexAvailable` should be the only source of truth of whether col_stats partition is ready to read in metadata table.



##########
hudi-spark-datasource/hudi-spark-common/src/main/scala/org/apache/hudi/HoodieFileIndex.scala:
##########
@@ -196,12 +191,20 @@ case class HoodieFileIndex(spark: SparkSession,
    * @return list of pruned (data-skipped) candidate base-files' names
    */
   private def lookupCandidateFilesInMetadataTable(queryFilters: Seq[Expression]): Try[Option[Set[String]]] = Try {
-    if (!isDataSkippingEnabled || queryFilters.isEmpty || !HoodieTableMetadataUtil.getCompletedMetadataPartitions(metaClient.getTableConfig)

Review Comment:
   The existing logic looks fine to me.  What's the gap here?



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