[GitHub] [beam] ibzib commented on a change in pull request #15174: [WIP][BEAM-12100][BEAM-10379][BEAM-9514] AssertionError type mismatch from AggregateScanConverter

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

ibzib commented on a change in pull request #15174:
URL: https://github.com/apache/beam/pull/15174#discussion_r683018811



##########
File path: sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/impl/rel/BeamAggregationRel.java
##########
@@ -246,6 +250,67 @@ private Transform(
 
       validateWindowIsSupported(windowedStream);
 
+      PTransform<PCollection<Row>, PCollection<Row>> combiner = createCombiner();
+
+      boolean verifyRowValues =
+          pinput.getPipeline().getOptions().as(BeamSqlPipelineOptions.class).getVerifyRowValues();
+      return windowedStream
+          .apply(combiner)
+          .apply(
+              "mergeRecord",
+              ParDo.of(mergeRecord(outputSchema, windowFieldIndex, ignoreValues, verifyRowValues)))
+          .setRowSchema(outputSchema);
+    }
+
+    private PTransform<PCollection<Row>, PCollection<Row>> createCombiner() {
+      // Check if have fields to be grouped
+      if (groupSetCount > 0) {
+        return createGroupCombiner();
+      }
+      return createGlobalCombiner();
+    }
+
+    private PTransform<PCollection<Row>, PCollection<Row>> createGlobalCombiner() {
+      org.apache.beam.sdk.schemas.transforms.Group.Global<Row> globally =
+          org.apache.beam.sdk.schemas.transforms.Group.globally();
+      org.apache.beam.sdk.schemas.transforms.Group.CombineFieldsGlobally<Row> combined = null;
+      for (FieldAggregation fieldAggregation : fieldAggregations) {
+        List<Integer> inputs = fieldAggregation.inputs;
+        CombineFn combineFn = fieldAggregation.combineFn;
+        if (inputs.size() > 1 || inputs.isEmpty()) {
+          // In this path we extract a Row (an empty row if inputs.isEmpty).
+          combined =
+              (combined == null)
+                  ? globally.aggregateFieldsById(inputs, combineFn, fieldAggregation.outputField)
+                  : combined.aggregateFieldsById(inputs, combineFn, fieldAggregation.outputField);
+        } else {
+          // Combining over a single field, so extract just that field.
+          combined =
+              (combined == null)
+                  ? globally.aggregateField(inputs.get(0), combineFn, fieldAggregation.outputField)
+                  : combined.aggregateField(inputs.get(0), combineFn, fieldAggregation.outputField);
+        }
+      }
+
+      PTransform<PCollection<Row>, PCollection<Row>> combiner = combined;
+      if (combiner == null) {
+        // If no field aggregations were specified, we run a constant combiner that always returns
+        // a single empty row for each key. This is used by the SELECT DISTINCT query plan - in this
+        // case a group by is generated to determine unique keys, and a constant null combiner is
+        // used.
+        combiner =
+            globally.aggregateField(
+                "*",
+                AggregationCombineFnAdapter.createConstantCombineFn(),
+                Field.of(
+                    "e",
+                    FieldType.row(AggregationCombineFnAdapter.EMPTY_SCHEMA).withNullable(true)));
+        ignoreValues = true;
+      }
+      return combiner;
+    }

Review comment:
       It looks like the incorrect null value is coming from here: https://github.com/apache/beam/blob/39cf3fccbb3950b9fd0c8938301d192c3ca85cce/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/Combine.java#L515
   
   You can fix it by overriding the `identity()` method in `LongSum`. Or maybe you could change it back to `Sum.ofLongs`, I'm not sure why it needed a separate definition here?




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