4ac385adc5
We are capable of optimizing MIN() and MAX() aggregates on indexed columns into subqueries that exploit the index, rather than the normal thing of scanning the whole table. When we do this, we replace the Aggref node(s) with Params referencing subquery outputs. Such Params really ought to be included in the per-plan-node extParam/allParam sets computed by SS_finalize_plan. However, we've never done so up to now because of an ancient implementation choice to perform that substitution during set_plan_references, which runs after SS_finalize_plan, so that SS_finalize_plan never sees these Params. The cleanest fix would be to perform a separate tree walk to do these substitutions before SS_finalize_plan runs. That seems unattractive, first because a whole-tree mutation pass is expensive, and second because we lack infrastructure for visiting expression subtrees in a Plan tree, so that we'd need a new function knowing as much as SS_finalize_plan knows about that. I also considered swapping the order of SS_finalize_plan and set_plan_references, but that fell foul of various assumptions that seem tricky to fix. So the approach adopted here is to teach SS_finalize_plan itself to check for such Aggrefs. I refactored things a bit in setrefs.c to avoid having three copies of the code that does that. Back-patch of v17 commits d0d44049d and 779ac2c74. When d0d44049d went in, there was no evidence that it was fixing a reachable bug, so I refrained from back-patching. Now we have such evidence. Per bug #18465 from Hal Takahara. Back-patch to all supported branches. Discussion: https://postgr.es/m/18465-2fae927718976b22@postgresql.org Discussion: https://postgr.es/m/2391880.1689025003@sss.pgh.pa.us
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. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download/ See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.