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https://issues.apache.org/jira/browse/FLINK-37814?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17952781#comment-17952781
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Stepan Stepanishchev commented on FLINK-37814:
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Hey! I'd be happy to do this.
> FLIP-516: Adjust FlinkJoinToMultiJoinRule for Multi Join Operator
> -----------------------------------------------------------------
>
> Key: FLINK-37814
> URL: https://issues.apache.org/jira/browse/FLINK-37814
> Project: Flink
> Issue Type: New Feature
> Reporter: Gustavo de Morais
> Priority: Major
>
> The current FlinkJoinToMultiJoinRule is implemented and only used for join
> reordering. We can use it as a base but we need a new set of optimizer rules
> for the multi way join operator:
>
> * Add FlinkLogicalMultiJoin with all parameters we need +
> FlinkJoinToFlinkMultiJoinRule to create it
> ** There are some parameters that calcite's MultiJoin does not contain as we
> require it. For example: we only have outerJoinConditions and we actually
> need all join conditions for each input level, including inner joins.
> * Add right join to left join rule - our operator only works with left joins
> * Check if the join chain respects the multi join common key restrictions
> ** If not, create one multi join for each group of joins that respect. That
> means 9 chained joins, 3 have one common key and 6 have another will generate
> two chained multi joins.
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