55918f798b
Previously the internal queue of buffers was capped at max_ios * 4, though not less than io_combine_limit, at allocation time. That was done in the first version based on conservative theories about resource usage and heuristics pending later work. The configured I/O depth could not always be reached with dense random streams generated by ANALYZE, VACUUM, the proposed Bitmap Heap Scan patch, and also sequential streams with the proposed AIO subsystem to name some examples. The new formula is (max_ios + 1) * io_combine_limit, enough buffers for the full configured I/O concurrency level using the full configured I/O combine size, plus the buffers from one finished but not yet consumed full-sized I/O. Significantly more memory would be needed for high GUC values if the client code requests a large per-buffer data size, but that is discouraged (existing and proposed stream users try to keep it under a few words, if not zero). With this new formula, an intermediate variable could have overflowed under maximum GUC values, so its data type is adjusted to cope. Discussion: https://postgr.es/m/CA%2BhUKGK_%3D4CVmMHvsHjOVrK6t4F%3DLBpFzsrr3R%2BaJYN8kcTfWg%40mail.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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.