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Before v14, a reltuples value of 0 was ambiguous: it could either mean the relation is empty, or it could mean that it hadn't yet been vacuumed or analyzed. (Commit3d351d916btaught v14 and newer to use -1 for the latter case.) This ambiguity allegedly can cause the planner to choose inefficient plans after restoring to v18 or newer. To fix, let's just dump reltuples as -1 in that case. This will cause some truly empty tables to be seen as not-yet-processed, but that seems unlikely to cause too much trouble in practice. Note that we could alternatively teach pg_restore_relation_stats() to translate reltuples based on the version argument, but since that function doesn't exist until v18, there's no particular advantage to that approach. That is, there's no chance of restoring stats dumped from a pre-v14 server to another pre-v14 server. Per discussion, the current policy is to fix pre-v18 behavior differences during export and everything else during import. Commit9879105024fixed a similar problem for vacuumdb by removing the check for reltuples != 0. Presumably we could reinstate that check now, but I've chosen to leave it in place in case reltuples isn't accurate. As before, processing some empty tables seems relatively harmless. Author: Hari Krishna Sunder <hari.db.pg@gmail.com> Reviewed-by: Jeff Davis <pgsql@j-davis.com> Reviewed-by: Corey Huinker <corey.huinker@gmail.com> Discussion: https://postgr.es/m/CAAeiqZ0o2p4SX5_xPcuAbbsmXjg6MJLNuPYSLUjC%3DWh-VeW64A%40mail.gmail.com
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/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/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/.