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In the various waiting phases of CREATE INDEX CONCURRENTLY (CIC) and REINDEX CONCURRENTLY (RC), we wait for other processes to release their snapshots; this is necessary in general for correctness. However, processes doing CIC in other tables cannot possibly affect CIC or RC done in "this" table, so we don't need to wait for those. This commit adds a flag in MyProc->statusFlags to indicate that the current process is doing CIC, so that other processes doing CIC or RC can ignore it when waiting. Note that this logic is only valid if the index does not access other tables. For simplicity we avoid setting the flag if the index has a column that's an expression, or has a WHERE predicate. (It is possible to have expressional or partial indexes that do not access other tables, but figuring that out would require more work.) This flag can potentially also be used by processes doing REINDEX CONCURRENTLY to be skipped; and by VACUUM to ignore processes in CIC or RC for the purposes of computing an Xmin. That's left for future commits. Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Author: Dimitry Dolgov <9erthalion6@gmail.com> Reviewed-by: Michael Paquier <michael@paquier.xyz> Discussion: https://postgr.es/m/20200810233815.GA18970@alvherre.pgsql
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/.