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Earlier, we use to postpone deleting empty pages till the second stage of vacuum to amortize the cost of scanning internal pages. However, that can sometimes (say vacuum is canceled or errored between first and second stage) delay the pages to be recycled. Another thing is that to facilitate deleting empty pages in the second stage, we need to share the information about internal and empty pages between different stages of vacuum. It will be quite tricky to share this information via DSM which is required for the upcoming parallel vacuum patch. Also, it will bring the logic to reclaim deleted pages closer to nbtree where we delete empty pages in each pass. Overall, the advantages of deleting empty pages in each pass outweigh the advantages of postponing the same. Author: Dilip Kumar, with changes by Amit Kapila Reviewed-by: Sawada Masahiko and Amit Kapila Discussion: https://postgr.es/m/CAA4eK1LGr+MN0xHZpJ2dfS8QNQ1a_aROKowZB+MPNep8FVtwAA@mail.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. 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/.