Jianhui Dong created FLINK-30396:
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Summary: sql hint 'LOOKUP' which is defined in outer query block
may take effect in inner query block
Key: FLINK-30396
URL: https://issues.apache.org/jira/browse/FLINK-30396
Project: Flink
Issue Type: Bug
Components: Table SQL / Planner
Affects Versions: 1.16.0
Reporter: Jianhui Dong
As [flink
doc|https://nightlies.apache.org/flink/flink-docs-master/docs/dev/table/sql/queries/hints/#query-hints]
said:
> {{Query hints}} can be used to suggest the optimizer to affect query
> execution plan within a specified query scope. Their effective scope is
> current {{{}Query block{}}}([What are query blocks
> ?|https://nightlies.apache.org/flink/flink-docs-master/docs/dev/table/sql/queries/hints/#what-are-query-blocks-])
> which {{Query Hints}} are specified.
But the sql hint 'LOOKUP' can ,like the demo following:
{code:java}
-- DDL
CREATE TABLE left_table (
lid INTEGER,
lname VARCHAR,
pts AS PROCTIME()
) WITH (
'connector' = 'filesystem',
'format' = 'csv',
'path'='xxx'
)
CREATE TABLE dim_table (
id INTEGER,
name VARCHAR,
mentor VARCHAR,
gender VARCHAR
) WITH (
'connector' = 'jdbc',
'url' = 'xxx',
'table-name' = 'dim1',
'username' = 'xxx',
'password' = 'xxx',
'driver'= 'com.mysql.cj.jdbc.Driver'
)
-- DML
SELECT /*+ LOOKUP('table'='outer') */
ll.id AS lid,
ll.name,
r.mentor,
r.gender
FROM (
SELECT /*+ LOOKUP('table'='inner') */
l.lid AS id,
l.lname AS name,
r.mentor,
r.gender,
l.pts
FROM left_table AS l
JOIN dim_table FOR SYSTEM_TIME AS OF l.pts AS r
ON l.lname = r.name
) ll JOIN dim_table FOR SYSTEM_TIME AS OF ll.pts AS r ON ll.name=r.name{code}
The inner correlate will have two hints: \{[LOOKUP inheritPath:[0]
options:{table=inner}], [LOOKUP inheritPath:[0, 0, 0] options:\{table=outer}]},
and IMO which maybe is a bug.
The reason for the above case is that the hint 'ALIAS' now only works for join
rel nodes and 'LOOKUP' works for correlate and join rel nodes.
I think maybe the better way would be to make 'ALIAS' support both correlate
and join rel nodes like 'LOOKUP'.
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