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Previously, the per-barrier-type functions tasked with absorbing them were expected to always succeed and never throw an error. However, that's a bit inconvenient. Further study has revealed that there are realistic cases where it might not be possible to absorb a ProcSignalBarrier without terminating the transaction, or even the whole backend. Similarly, for some barrier types, there might be other reasons where it's not reasonably possible to absorb the barrier at certain points in the code, so provide a way for a per-barrier-type function to reject absorbing the barrier. Unfortunately, there's still no committed code making use of this infrastructure; hopefully, we'll get there. :-( Patch by me, reviewed by Andres Freund and Amul Sul. Discussion: http://postgr.es/m/20200908182005.xya7wetdh3pndzim@alap3.anarazel.de Discussion: http://postgr.es/m/CA+Tgmob56Pk1-5aTJdVPCWFHon7me4M96ENpGe9n_R4JUjjhZA@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/.