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https://issues.apache.org/jira/browse/CALCITE-4592?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17337017#comment-17337017
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Amandeep Sharma commented on CALCITE-4592:
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[~julianhyde], [~Chunwei Lei] I have added the unit test. Fix can be commented
out to reproduce the issue using the unit test.
> RelToSqlConverter#visit(Join e) does not populate correlation context
> ---------------------------------------------------------------------
>
> Key: CALCITE-4592
> URL: https://issues.apache.org/jira/browse/CALCITE-4592
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.26.0
> Reporter: Amandeep Sharma
> Priority: Major
> Labels: pull-request-available
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Correlation context is populated for the followings:
> * Project
> * Filter
> * Calc
> * Correlate
> But it is not populated for _Join._ Because of it, using joiner's correlation
> id causes below exception
> {code:java}
> Caused by:
> java.lang.NullPointerException
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$Context.toSql(SqlImplementor.java:506)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$Context.toSql(SqlImplementor.java:828)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$Context.toSql(SqlImplementor.java:668)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$Context.toSql(SqlImplementor.java:828)
> at
> org.apache.calcite.rel.rel2sql.SqlImplementor$Context.toSql(SqlImplementor.java:668)
> at
> org.apache.calcite.rel.rel2sql.RelToSqlConverter.visit(RelToSqlConverter.java:213)
> ... 65 more
> {code}
>
> Use case is to generate below query/ query with same semantic, having a
> scalar sub-query with correlated condition in the projection:
> {code:java}
> SELECT
> CUSTOMER.CUSTOMER_ID, --RexInputRef from join
> CUSTOMER.NAME, -- RexInputRef from join
> PAYMENT.PAYMENT_ID, -- RexInputRef from join
> (SELECT PAYMENT.AMOUNT FROM PAYMENT WHERE CUSTOMER.CUSTOMER_ID =
> PAYMENT.CUSTOMER_ID) AS AMOUNT --RexSubQuery
> FROM CUSTOMER LEFT JOIN PAYMENT ON CUSTOMER.CUSTOMER_ID =
> PAYMENT.CUSTOMER_ID; --$cor0
> {code}
> *Schema Tables*
> {code:java}
> CUSTOMER
> +- CUSTOMER_ID
> +- NAME
> PAYMENT
> +-PAYMENT_ID
> +-CUSTOMER_ID
> +-AMOUNT
> {code}
> For scalar sub-query, the input table is PAYMENT.
> Join's correlated field CUSTOMER_ID ($cor0.CUSTOMER_ID) needs to be binded in
> the scalar sub-query's condition: $cor0.CUSTOMER_ID = $1
> While materializing correlated field, it will be resolved to the CUSTOMER
> table's CUSTOMER_ID field.
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