Based on Toms feedback, and due to the fact that SQL:2021 forbids non-linear recursion, version 2 of the patch allows only linear recursion. Therefore, later SQL committee decisions on non-linear recursion should not be problematic. > [LIN] PostgreSQL does not allow multiple references to the recursive > common table, even if the recursion is LINEAR. Plenty of examples > of such queries are found in the documentation of established RDBMSs, > among these IBM Db2 and MS SQL Server: > > - https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_73/sqlp/rbafyrecursivequeries.htm#d60691e2455 > (example "Two tables used for recursion using recursive common > table expressions") See the gist at [1] below for SQL code that features multiple (yet linear) recursive references. A patched PostgreSQL runs this query as expected. Best wishes, --Denis and Torsten |
0002-Allow-multiple-recursive-self-references.patch
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