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A "break" statement erroneously left behind by commit a1c1af2a1 caused TopoSort to do the wrong thing if a lock's wait list contained multiple members of the same locking group. Because parallel workers don't normally need any locks not already taken by their leader, this is very hard --- maybe impossible --- to hit in production. Still, if it did happen, the queries involved in an otherwise-resolvable deadlock would block until canceled. In addition to removing the bogus "break", add an Assert showing that the conflicting uses of the beforeConstraints[] array (for both counts and flags) don't overlap, and add some commentary explaining why not; because it's not obvious without explanation, IMHO. Original report and patch from Rui Hai Jiang; additional assert and commentary by me. Back-patch to 9.6 where the bug came in. Discussion: https://postgr.es/m/CAEri+mLd3bpHLyW+a9pSe1y=aEkeuJpwBSwvo-+m4n7-ceRmXw@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/.