[jira] [Assigned] (CALCITE-2129) RelToSqlConverter incorrectly projects aggregate function from sub-query

["Atri Sharma (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-2129?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Atri Sharma reassigned CALCITE-2129:
------------------------------------

    Assignee: Atri Sharma  (was: Julian Hyde)

> RelToSqlConverter incorrectly projects aggregate function from sub-query
> ------------------------------------------------------------------------
>
>                 Key: CALCITE-2129
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2129
>             Project: Calcite
>          Issue Type: Bug
>          Components: core, jdbc-adapter
>    Affects Versions: 1.15.0
>            Reporter: Paul Jackson
>            Assignee: Atri Sharma
>            Priority: Major
>
> Starting with this DDL:
> {code:SQL}
> create table friends (
>   id int not null,
>   friend_id int,
>   primary key (id),
>   foreign key (friend_id) references friends (id)
> );
> insert into friends values
> (210, null),
> (209, 210),
> (202, 209),
> (208, 202),
> (207, 209),
> (203, 207),
> (201, null),
> (204, null),
> (205, null),
> (206, 209);
> {code}
> This query gives the highest id of friends that share friend_id for each friend:
> {code:SQL}
> SELECT id, friend_id,
>  (SELECT max(f2.id)
>   FROM friends AS f2
>   WHERE f2.friend_id = f1.friend_id) AS foaf_id
> FROM friends AS f1
> id	friend	foaf
> 201		
> 202	209	207
> 203	207	203
> 204		
> 205		
> 206	209	207
> 207	209	207
> 208	202	208
> 209	210	209
> 210
> {code}	
> I convert this query to a RelNode and then converted it back to SQL:
> {code:Java}
> Planner aPlanner = Frameworks.getPlanner(aConfig);
> SqlNode aQuery = aPlanner.parse(theSql);
> aQuery = aPlanner.validate(aQuery);
> RelNode aRelNode = aPlanner.rel(aQuery).project();
> RelToSqlConverter aSqlConverter = new RelToSqlConverter(aSqlDialect);
> SqlNode aSqlNode = aSqlConverter.visitChild(0, aRelNode).asStatement();
> {code}
> This gives the following plan and SQL:
> {code}
> LogicalProject(id=[$0], friend_id=[$1], foaf_id=[$2])
>   LogicalProject(id=[$0], friend_id=[$1], EXPR$0=[$3])
>     LogicalJoin(condition=[=($1, $2)], joinType=[left])
>       JdbcTableScan(table=[[stardog, friends]])
>       LogicalAggregate(group=[{0}], EXPR$0=[MAX($1)])
>         LogicalProject(friend_id=[$1], id=[$0])
>           LogicalProject(id=[$0], friend_id=[$1])
>             LogicalFilter(condition=[IS NOT NULL($1)])
>               JdbcTableScan(table=[[stardog, friends]])
> SELECT `friends`.`id`, `friends`.`friend_id`, MAX(`id`)
> FROM `stardog`.`friends`
> LEFT JOIN (SELECT `friend_id`, MAX(`id`)
> FROM `stardog`.`friends`
> WHERE `friend_id` IS NOT NULL
> GROUP BY `friend_id`) AS `t1` ON `friends`.`friend_id` = `t1`.`friend_id`
> {code}
> This is a bad conversion. The {{MAX(`id`)}} should not be repeated in the outer select. PostgreSQL will complain that the aggregating function requires a group by. MySQL returns the max id that has a non-null friend (208), that id's friend (202), and the max id of all rows (210):
> {code}
> id	friend	MAX(`id`)
> 208	202	210
> {code}
> I think the correct SQL should be:
> {code:SQL}
> SELECT `friends`.`id`, `friends`.`friend_id`, foaf_id
> FROM `stardog`.`friends`
> LEFT JOIN (SELECT `friend_id`, MAX(`id`) AS foaf_id
> FROM `stardog`.`friends`
> WHERE `friend_id` IS NOT NULL
> GROUP BY `friend_id`) AS `t1` ON `friends`.`friend_id` = `t1`.`friend_id`
> {code}
> There is code in {{SqlImplementor}} and {{RelToSqlConverter}} that uses an {{ordinalMap}} to track what functions are aliases as what identifiers. When the SQL is generated, the identifier is replaced with the function. If all that code is removed, this works as expected (using {{EXPR$0}} as the alias rather than {{foaf_id}}).



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