[GitHub] [incubator-pinot] kishoreg commented on a change in pull request #5147: Support default star-tree

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

kishoreg commented on a change in pull request #5147: Support default star-tree
URL: https://github.com/apache/incubator-pinot/pull/5147#discussion_r393247188
 
 

 ##########
 File path: pinot-core/src/main/java/org/apache/pinot/core/startree/v2/builder/StarTreeV2BuilderConfig.java
 ##########
 @@ -58,6 +69,73 @@ public static StarTreeV2BuilderConfig fromIndexConfig(StarTreeIndexConfig indexC
     return builder.build();
   }
 
+  /**
+   * Generates default config based on the segment metadata.
+   * <ul>
+   *   <li>
+   *     All dictionary-encoded single-value dimensions (including date-time columns) with cardinality smaller or equal
+   *     to the threshold will be included in the split order, sorted by their cardinality in descending order
+   *   </li>
+   *   <li>Time column (if exists and dictionary-encoded) will be appended to the split order as the last element</li>
+   *   <li>Use COUNT(*) and SUM for all numeric metrics as function column pairs</li>
+   *   <li>Use default value for max leaf records</li>
+   * </ul>
+   */
+  public static StarTreeV2BuilderConfig generateDefaultConfig(SegmentMetadataImpl segmentMetadata) {
+    Schema schema = segmentMetadata.getSchema();
+    List<ColumnMetadata> dimensionColumnMetadataList = new ArrayList<>();
+    String timeColumn = null;
+    List<String> numericMetrics = new ArrayList<>();
+
+    for (FieldSpec fieldSpec : schema.getAllFieldSpecs()) {
+      if (!fieldSpec.isSingleValueField() || fieldSpec.isVirtualColumn()) {
+        continue;
+      }
+      String column = fieldSpec.getName();
+      switch (fieldSpec.getFieldType()) {
+        case DIMENSION:
+        case DATE_TIME:
+          ColumnMetadata columnMetadata = segmentMetadata.getColumnMetadataFor(column);
 
 Review comment:
   why are we checking the cardinality threshold for date_time but not for time?

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