[GitHub] [incubator-pinot] fx19880617 commented on a change in pull request #6494: Support generating derived column during segment load

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

fx19880617 commented on a change in pull request #6494:
URL: https://github.com/apache/incubator-pinot/pull/6494#discussion_r564951218



##########
File path: pinot-core/src/main/java/org/apache/pinot/core/segment/index/loader/defaultcolumn/BaseDefaultColumnHandler.java
##########
@@ -324,8 +345,69 @@ protected void removeColumnV1Indices(String column)
    */
   protected void createColumnV1Indices(String column)
       throws Exception {
+    TableConfig tableConfig = _indexLoadingConfig.getTableConfig();
+    if (tableConfig != null && tableConfig.getIngestionConfig() != null
+        && tableConfig.getIngestionConfig().getTransformConfigs() != null) {
+      List<TransformConfig> transformConfigs = tableConfig.getIngestionConfig().getTransformConfigs();
+      for (TransformConfig transformConfig : transformConfigs) {
+        if (transformConfig.getColumnName().equals(column)) {
+          String transformFunction = transformConfig.getTransformFunction();
+          FunctionEvaluator functionEvaluator = FunctionEvaluatorFactory.getExpressionEvaluator(transformFunction);
+
+          // Check if all arguments exist in the segment
+          // TODO: Support chained derived column
+          boolean skipCreatingDerivedColumn = false;
+          List<String> arguments = functionEvaluator.getArguments();
+          List<ColumnMetadata> argumentsMetadata = new ArrayList<>(arguments.size());
+          for (String argument : arguments) {
+            ColumnMetadata columnMetadata = _segmentMetadata.getColumnMetadataFor(argument);
+            if (columnMetadata == null) {
+              LOGGER.warn(
+                  "Skip creating derived column: {} because argument: {} does not exist in the segment, creating default value column instead",
+                  column, argument);
+              skipCreatingDerivedColumn = true;
+              break;
+            }
+            argumentsMetadata.add(columnMetadata);
+          }
+          if (skipCreatingDerivedColumn) {
+            break;
+          }
+
+          // TODO: Support raw derived column
+          if (_indexLoadingConfig.getNoDictionaryColumns().contains(column)) {
+            LOGGER.warn("Skip creating raw derived column: {}, creating default value column instead", column);
+            break;
+          }
+
+          // TODO: Support multi-value derived column
+          if (!_schema.getFieldSpecFor(column).isSingleValueField()) {
+            LOGGER.warn("Skip creating MV derived column: {}, creating default value column instead", column);
+            break;
+          }
+
+          try {
+            createDerivedColumnV1Indices(column, functionEvaluator, argumentsMetadata);
+            return;
+          } catch (Exception e) {
+            LOGGER.error(

Review comment:
       If the user misconfigured the transform function and found out the values are all default values, is there a way to fix this?
   E.g. I can force re-generate the derived column.




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