e676bdac1a
If a MERGE command contains WHEN NOT MATCHED BY SOURCE actions, the source relation appears on the outer side of the join. Thus, any Vars referring to the source in the merge join condition, actions, and RETURNING list should be marked as nullable by the join, since they are used in the ModifyTable node above the join. Note that this only applies to the copy of join condition used in the executor to distinguish MATCHED from NOT MATCHED BY SOURCE cases. Vars in the original join condition, inside the join node itself, should not be marked. Failure to correctly mark these Vars led to a "wrong varnullingrels" error in the final stage of query planning, in some circumstances. We happened to get away without this in all previous tests, since they all involved a ModifyTable node directly on top of the join node, so that the top plan targetlist coincided with the output of the join, and the varnullingrels check was more lax. However, if another plan node, such as a one-time filter Result node, gets inserted between the ModifyTable node and the join node, then a stricter check is applied, which fails. Per bug #18634 from Alexander Lakhin. Thanks to Tom Lane and Richard Guo for review and analysis. Back-patch to v17, where WHEN NOT MATCHED BY SOURCE support was added to MERGE. Discussion: https://postgr.es/m/18634-db5299c937877f2b%40postgresql.org
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/17/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/17/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.