AMashenkov commented on code in PR #3413:
URL: https://github.com/apache/ignite-3/pull/3413#discussion_r1532074928
##########
modules/sql-engine/src/main/java/org/apache/ignite/internal/sql/engine/rel/agg/MapReduceAggregates.java:
##########
@@ -356,10 +486,190 @@ private static MapReduceAgg
createSimpleAgg(AggregateCall call, int reduceArgume
return new MapReduceAgg(argList, call, reduceCall, USE_INPUT_FIELD);
}
+ /**
+ * TODO: Rename to MakeExpr.
+ * Produces intermediate expressions that modify results of MAP/REDUCE
aggregate.
+ * For example: after splitting a function into a MAP aggregate and REDUCE
aggregate it is necessary to add casts to
+ * output of a REDUCE phase aggregate.
+ *
+ * <p>In order to avoid creating unnecessary projections, use {@link
MapReduceAggregates#USE_INPUT_FIELD}.
+ */
@FunctionalInterface
private interface MakeReduceExpr {
- /** Creates an expression that produces result of REDUCE phase of an
aggregate. */
+ /**
+ * Creates an expression that applies a performs computation (e.g.
applies some function, adds a cast)
+ * on {@code args} fields of input relation.
+ *
+ * @param rexBuilder Expression builder.
+ * @param input Input relation.
+ * @param args Arguments.
+ * @param typeFactory Type factory.
+ *
+ * @return Expression.
+ */
RexNode makeExpr(RexBuilder rexBuilder, RelNode input, List<Integer>
args, IgniteTypeFactory typeFactory);
}
+
+ private static MapReduceAgg createAvgAgg(
+ RelOptCluster cluster,
+ AggregateCall call,
+ int reduceArgumentOffset,
+ RelDataType inputType,
+ boolean canBeNull
+ ) {
+ RelDataTypeFactory tf = cluster.getTypeFactory();
+ RelDataTypeSystem typeSystem = tf.getTypeSystem();
+
+ RelDataType fieldType =
inputType.getFieldList().get(call.getArgList().get(0)).getType();
+
+ // In case of AVG(NULL) return a simple version of an aggregate,
because result is always NULL.
+ if (fieldType.getSqlTypeName() == SqlTypeName.NULL) {
+ return createSimpleAgg(call, reduceArgumentOffset);
+ }
+
+ // AVG(x) : SUM(x)/COUNT0(x)
+ // MAP : SUM(x) / COUNT(x)
+
+ // SUM(x) as s
+ RelDataType mapSumType = typeSystem.deriveSumType(tf, fieldType);
+ if (canBeNull) {
+ mapSumType = tf.createTypeWithNullability(mapSumType, true);
+ }
+
+ AggregateCall mapSum0 = AggregateCall.create(
+ SqlStdOperatorTable.SUM,
+ call.isDistinct(),
+ call.isApproximate(),
+ call.ignoreNulls(),
+ ImmutableList.of(),
+ call.getArgList(),
+ call.filterArg,
+ null,
+ call.collation,
+ mapSumType,
+ "AVG" + reduceArgumentOffset + "_MAP_SUM");
+
+ // COUNT(x) as c
+ RelDataType mapCountType = tf.createSqlType(SqlTypeName.BIGINT);
+
+ AggregateCall mapCount0 = AggregateCall.create(
+ SqlStdOperatorTable.COUNT,
+ call.isDistinct(),
+ call.isApproximate(),
+ call.ignoreNulls(),
+ ImmutableList.of(),
+ call.getArgList(),
+ call.filterArg,
+ null,
+ call.collation,
+ mapCountType,
+ "AVG" + reduceArgumentOffset + "_MAP_COUNT");
+
+ // REDUCE : SUM0(s) as reduce_sum, SUM0(c) as reduce_count
Review Comment:
```suggestion
// REDUCE : SUM(s) as reduce_sum, SUM0(c) as reduce_count
```
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