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https://issues.apache.org/jira/browse/FLINK-38444?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gustavo de Morais reassigned FLINK-38444:
-----------------------------------------
Assignee: Gustavo de Morais
> Join calculates upsert keys with null keys for left join
> --------------------------------------------------------
>
> Key: FLINK-38444
> URL: https://issues.apache.org/jira/browse/FLINK-38444
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Planner
> Reporter: Gustavo de Morais
> Assignee: Gustavo de Morais
> Priority: Major
> Labels: pull-request-available
> Fix For: 2.2.0
>
>
> The planner currently considers the union of both the upsert keys from the
> left and from the right to be a valid resulting upsert key. That's true for
> inner joins but for left joins that leads to a resulting upsert key that
> contains columns that can be null, which is not valid.
> Example and simplified repro steps:
> {code:java}
> -- Table 'orders' with an incomplete primary key
> CREATE TABLE `orders_with_composite_key` (
> `order_id` BIGINT NOT NULL,
> `user_id` INT NOT NULL,
> `item_name` STRING,
> CONSTRAINT `PRIMARY` PRIMARY KEY (`order_id`, `user_id`) NOT ENFORCED
> );
>
> -- Table 'users'
> CREATE TABLE `users` (
> `user_id` INT NOT NULL,
> `other_data` STRING,
> CONSTRAINT `PRIMARY` PRIMARY KEY (`user_id`) NOT ENFORCED
> );
> SELECT
> o.user_id,
> o.order_id,
> u.user_id
> FROM `users` AS u
> LEFT JOIN `orders_with_composite_key` AS o
> ON o.user_id = u.user_id
> -- Bug: this incorrectly infers the following upsert join from the join
> (user_id,order_id,user_id0)
> {code}
> This is not valid since the columns on the right can be null and can't be
> used as part of an upsert key.
> This is where we calculate the unique keys and where we need to consider the
> nullability of the fields as we do for the other cases below
> [https://github.com/apache/flink/blob/master/flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/plan/metadata/FlinkRelMdUniqueKeys.scala#L593]
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