c5b2818413
Further thought about bug #17050 suggests that it's a good idea to use CURSOR_OPT_NO_SCROLL for the implicit cursor opened by a plpgsql FOR-over-query loop. This ensures that, if somebody commits inside the loop, PersistHoldablePortal won't try to rewind and re-read the cursor. While we'd have selected NO_SCROLL anyway if FOR UPDATE/SHARE appears in the query, there are other hazards with volatile functions; and in any case, it's silly to expend effort storing rows that we know for certain won't be needed. (While here, improve the comment in exec_run_select, which was a bit confused about the rationale for when we can use parallel mode. Cursor operations aren't a hazard for nameless portals.) This wasn't an issue until v11, which introduced the possibility of persisting such cursors. Hence, back-patch to v11. Per bug #17050 from Алексей Булгаков. Discussion: https://postgr.es/m/17050-f77aa827dc85247c@postgresql.org |
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README
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/.