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https://issues.apache.org/jira/browse/FLINK-4565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15503481#comment-15503481
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Timo Walther commented on FLINK-4565:
-------------------------------------
I looked into the code for this issue. It would be very tricky to support IN
for the Table API as we currently separate expressions ({{RexNodes}}) from
operators ({{RelNodes}}).
In the end we would need to call something similar to
{{org.apache.calcite.sql2rel.SqlToRelConverter.Blackboard#convertExpression}}
{code}
final RexSubQuery in = RexSubQuery.in(root.rel, builder.build());
return op.isNotIn()
? rexBuilder.makeCall(SqlStdOperatorTable.NOT, in)
: in;
{code}
{{RexSubQuery}} is a rex node, however, it needs access to
{{Table}}/{{LogicalNode}} to get the {{RelNode}}.
The following steps need to be implemented:
- For Java API: Create a {{UnresolvedTableReference}} expression that takes the
name of the table.
- For Java API: Resolve the name of the table in
{{org.apache.flink.api.table.plan.logical.LogicalNode#resolveExpressions}} to
{{TableReference}} using the table environment that is available in this
method. {{TableReference}} then has a {{Table}} field.
- Create an expression {{In}} that takes a {{TableReference}} and does the
above code snippet in {{toRexNode}}.
[~chobeat] I hope this helps otherwise it also fine if you let someone else
implement this.
> Support for SQL IN operator
> ---------------------------
>
> Key: FLINK-4565
> URL: https://issues.apache.org/jira/browse/FLINK-4565
> Project: Flink
> Issue Type: Improvement
> Components: Table API & SQL
> Reporter: Timo Walther
> Assignee: Simone Robutti
>
> It seems that Flink SQL supports the uncorrelated sub-query IN operator. But
> it should also be available in the Table API and tested.
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