[jira] [Commented] (CALCITE-3101) PushDownJoinConditions is not always a valid transformation

["Haisheng Yuan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-3101?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16855555#comment-16855555 ] 

Haisheng Yuan commented on CALCITE-3101:
----------------------------------------

What is the point of generating this plan?

{code:java}
LogicalJoin(condition=[AND(=($3, $8), $10)], joinType=[inner])
 JdbcTableScan(table=[[XYZ, EMP]])
 LogicalProject(empno=[$0], ename=[$1], job=[$2], deptno=[$3], etype=[$4], $f5=[IS NOT NULL($1)])
 JdbcTableScan(table=[[XYZ, EMP]])
{code}

If we push the join condition down, we should have the following plan instead of above plan.

{code:java}
LogicalJoin(condition=[=($3, $8)], joinType=[inner])
 JdbcTableScan(table=[[XYZ, EMP]])
 LogicalFilter(condition=[IS NOT NULL($1)])
 JdbcTableScan(table=[[XYZ, EMP]])
{code}



> PushDownJoinConditions is not always a valid transformation
> -----------------------------------------------------------
>
>                 Key: CALCITE-3101
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3101
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.16.0
>         Environment: Java app pointing to Oracle database.
>            Reporter: Paul Jackson
>            Priority: Major
>
> SqlToRelConverter can create a plan that is invalid when converted back to SQL in cases where the expression that is pushed to the projection returns a Boolean. The following example pushes IS NOT NULL to a select. Several SQL dialects do not support this. Oracle, for example, sees IS NOT NULL as a condition rather than an expression. It returns a Boolean data type, which is not supported. Likewise, Microsoft SQL Server does not support IS NOT NULL in a projection expression.
> Steps to reproduce (Oracle):
> DDL:
> {code:java}
> CREATE TABLE "EMP" (
>  "empno" INTEGER PRIMARY KEY NOT NULL,
>  "ename" VARCHAR(100),
> "deptno" INTEGER);{code}
> Start with this query:
> {code:java}
> SELECT "EMP"."empno", "t"."ename" "ename0"
> FROM "EMP"
> INNER JOIN "EMP" "t"
> ON "EMP"."deptno" = "t"."deptno" AND "t"."ename" IS NOT NULL{code}
> Parse using {{SqlToRelConverter.convertQuery()}}. At this point in the stack trace:
> {noformat}
> org.apache.calcite.plan.RelOptUtil.pushDownJoinConditions(RelOptUtil.java:3222)
> org.apache.calcite.sql2rel.SqlToRelConverter.createJoin(SqlToRelConverter.java:2414)
> org.apache.calcite.sql2rel.SqlToRelConverter.convertFrom(SqlToRelConverter.java:2056)
> org.apache.calcite.sql2rel.SqlToRelConverter.convertSelectImpl(SqlToRelConverter.java:641)
> org.apache.calcite.sql2rel.SqlToRelConverter.convertSelect(SqlToRelConverter.java:622)
> org.apache.calcite.sql2rel.SqlToRelConverter.convertQueryRecursive(SqlToRelConverter.java:3057)
> org.apache.calcite.sql2rel.SqlToRelConverter.convertQuery(SqlToRelConverter.java:558)
> {noformat}
> the {{RelNode}} is:
> {noformat}
> LogicalJoin(condition=[AND(=($3, $8), IS NOT NULL($6))], joinType=[inner])
>  JdbcTableScan(table=[[XYZ, EMP]])
>  JdbcTableScan(table=[[XYZ, EMP]])
> {noformat}
> After {{pushDownJoinConditions}} the {{RelNode}} is:
> {noformat}
> LogicalJoin(condition=[AND(=($3, $8), $10)], joinType=[inner])
>  JdbcTableScan(table=[[XYZ, EMP]])
>  LogicalProject(empno=[$0], ename=[$1], job=[$2], deptno=[$3], etype=[$4], $f5=[IS NOT NULL($1)])
>  JdbcTableScan(table=[[XYZ, EMP]])
> {noformat}
> Which leads to invalid SQL ("ORA-00923: FROM keyword not found where expected"):
> {code:java}
> SELECT "EMP"."empno", "t"."ename" "ename0"
> FROM "XYZ"."EMP"
> INNER JOIN (
>     SELECT "empno", "ename", "job", "deptno", "etype", "ename" IS NOT NULL "$f5"
>     FROM "XYZ"."EMP") "t"
> ON "EMP"."deptno" = "t"."deptno" AND "t"."$f5"
> {code}



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