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Base de données relationnelle
6bc1fd4e60
Some of the ambuildempty functions used smgrwrite() directly, followed by smgrimmedsync(). A few small problems with that: Firstly, one is supposed to use smgrextend() when extending a relation, not smgrwrite(). It doesn't make much difference in production builds. smgrextend() updates the relation size cache, so you miss that, but that's harmless because we never use the cached relation size of an init fork. But if you compile with CHECK_WRITE_VS_EXTEND, you get an assertion failure. Secondly, the smgrwrite() calls were performed before WAL-logging, so the page image written to disk had 0/0 as the LSN, not the LSN of the WAL record. That's also harmless in practice, but seems sloppy. Thirdly, it's better to use the buffer cache, because then you don't need to smgrimmedsync() the relation to disk, which adds latency. Bypassing the cache makes sense for bulk operations like index creation, but not when you're just initializing an empty index. Creation of unlogged tables is hardly performance bottleneck in any real world applications, but nevertheless. Backpatch to v16, but no further. These issues should be harmless in practice, so better to not rock the boat in older branches. Reviewed-by: Robert Haas Discussion: https://www.postgresql.org/message-id/6e5bbc08-cdfc-b2b3-9e23-1a914b9850a9@iki.fi |
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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/.