godfrey he created FLINK-12192:
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Summary: Add support for generating optimized logical plan for
grouping sets and distinct aggregate
Key: FLINK-12192
URL: https://issues.apache.org/jira/browse/FLINK-12192
Project: Flink
Issue Type: New Feature
Components: Table SQL / Planner
Reporter: godfrey he
Assignee: godfrey he
This issue aims to supports generating optimized logical plan for grouping sets
and distinct aggregate. (mentioned in
[FLINK-12076|https://issues.apache.org/jira/browse/FLINK-12076] and
[FLINK-12098|https://issues.apache.org/jira/browse/FLINK-12098])
for batch, query with distinct aggregate will be rewritten into two
non-distinct aggregates by extended
[AggregateExpandDistinctAggregatesRule|https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/rules/AggregateExpandDistinctAggregatesRule.java],
the first aggregate computes the distinct result and non-distinct aggregate
function result, and the second aggregate computes the distinct aggregate
function result based on first aggregate result. The first aggregate has
grouping sets if there are more than one distinct aggregate on different fields.
for stream, query with distinct aggregate is handled by SplitAggregateRule in
[FLINK-12161|https://issues.apache.org/jira/browse/FLINK-12161].
query with grouping sets (or cube, rollup) will be rewritten into a regular
aggregate with expand.
The expand node will duplicates the input data for each simple group.
e.g.
{noformat}
schema:
MyTable: a: INT, b: BIGINT, c: VARCHAR(32), d: VARCHAR(32)
Original records:
+-----+-----+-----+-----+
| a | b | c | d |
+-----+-----+-----+-----+
| 1 | 1 | c1 | d1 |
+-----+-----+-----+-----+
| 1 | 2 | c1 | d2 |
+-----+-----+-----+-----+
| 2 | 1 | c1 | d1 |
+-----+-----+-----+-----+
SELECT a, c, SUM(b) as b FROM MyTable GROUP BY GROUPING SETS (a, c)
logical plan after expanded:
LogicalCalc(expr#0..3=[{inputs}], proj#0..1=[{exprs}], b=[$t3])
LogicalAggregate(group=[{0, 2, 3}], groups=[[]], b=[SUM($1)])
LogicalExpand(projects=[{a=[$0], b=[$1], c=[null], $e=[1]}, {a=[null],
b=[$1], c=[$2], $e=[2]}])
LogicalNativeTableScan(table=[[builtin, default, MyTable]])
notes:
'$e = 1' is equivalent to 'group by a'
'$e = 2' is equivalent to 'group by c'
expanded records:
+-----+-----+-----+-----+
| a | b | c | $e |
+-----+-----+-----+-----+ ---+---
| 1 | 1 | null| 1 | |
+-----+-----+-----+-----+ records expanded by record1
| null| 1 | c1 | 2 | |
+-----+-----+-----+-----+ ---+---
| 1 | 2 | null| 1 | |
+-----+-----+-----+-----+ records expanded by record2
| null| 2 | c1 | 2 | |
+-----+-----+-----+-----+ ---+---
| 2 | 1 | null| 1 | |
+-----+-----+-----+-----+ records expanded by record3
| null| 1 | c1 | 2 | |
+-----+-----+-----+-----+ ---+---
{noformat}
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