xuzifu666 commented on code in PR #5165:
URL: https://github.com/apache/calcite/pull/5165#discussion_r3754805402
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core/src/main/java/org/apache/calcite/tools/RelBuilder.java:
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@@ -5114,12 +5114,73 @@ private OverCall
orderBy_(ImmutableList<RexFieldCollation> sortKeys) {
}
};
final RelDataType type = op.inferReturnType(bind);
+ final ImmutableList<RexNode> newPartitionKeys =
+ simplifyPartitionKeys(partitionKeys);
+ final ImmutableList<RexFieldCollation> newSortKeys =
+ simplifySortKeys(newPartitionKeys, sortKeys);
final RexNode over = getRexBuilder()
- .makeOver(pos, type, op, operands, partitionKeys, sortKeys,
+ .makeOver(pos, type, op, operands, newPartitionKeys, newSortKeys,
lowerBound, upperBound, exclude, rows, allowPartial,
nullWhenCountZero,
distinct, ignoreNulls);
return aliasMaybe(over, alias);
}
+
+ /** Removes constant keys from a window's {@code PARTITION BY}. A constant
+ * partition key places every row in the same partition, so it does not
+ * partition the data and can be dropped. */
+ private ImmutableList<RexNode> simplifyPartitionKeys(
+ List<RexNode> partitionKeys) {
+ final ImmutableList.Builder<RexNode> newKeys = ImmutableList.builder();
+ for (RexNode key : partitionKeys) {
+ if (!RexUtil.isConstant(key)) {
+ newKeys.add(key);
+ }
+ }
+ return newKeys.build();
+ }
+
+ /** Removes redundant keys from a window's {@code ORDER BY}. A sort key is
+ * redundant if it is constant, or if it is functionally determined by the
+ * partition keys and earlier sort keys (those columns are fixed within a
+ * partition, so the key cannot affect the ordering). For example, with
+ * {@code PARTITION BY x, y ORDER BY x + y, z} the key {@code x + y} only
+ * references fixed columns and is dropped, leaving {@code ORDER BY z}. */
+ private ImmutableList<RexFieldCollation> simplifySortKeys(
+ List<RexNode> partitionKeys, List<RexFieldCollation> sortKeys) {
+ // A RANGE frame with a value offset (e.g. RANGE BETWEEN 5 PRECEDING)
Review Comment:
Thank you for pointing out, I had added a test
`testProjectOverRangeOffsetKeepsSortKey` to cover it. The new test would fail
without the following modification.
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