godfrey he created FLINK-6326:
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Summary: add ProjectMergeRule at logical optimization stage
Key: FLINK-6326
URL: https://issues.apache.org/jira/browse/FLINK-6326
Project: Flink
Issue Type: New Feature
Components: Table API & SQL
Reporter: godfrey he
Assignee: godfrey he
add ProjectMergeRule to merge projections. without this rule, some SQLs can not
push projection into scan.
e.g.
table1: id: int, name: string
table2: id: string, score: double, first: string, last: string
{code}
SELECT a.id, b.score FROM
(SELECT id FROM table1 WHERE id > 10) a
LEFT OUTER JOIN
(SELECT * FROM table2) b
ON CAST(a.id AS VARCHAR) = b.id
{code}
{code}
== Optimized Logical Plan without ProjectMergeRule ==
DataSetCalc(select=[id, score])
DataSetJoin(where=[=(id0, id1)], join=[id, id0, id1, score, first, last],
joinType=[LeftOuterJoin])
DataSetCalc(select=[id, CAST(id) AS id0], where=[>(id, 10)])
BatchTableSourceScan(table=[[table1]], fields=[id])
BatchTableSourceScan(table=[[table2]], fields=[id, score, first, last])
{code}
{code}
== Optimized Logical Plan with ProjectMergeRule ==
DataSetCalc(select=[id, score])
DataSetJoin(where=[=(id0, id1)], join=[id, id0, id1, score],
joinType=[LeftOuterJoin])
DataSetCalc(select=[id, CAST(id) AS id0], where=[>(id, 10)])
BatchTableSourceScan(table=[[table1]], fields=[id])
BatchTableSourceScan(table=[[table2]], fields=[id, score])
{code}
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