d8a859d22b
Previously, this was 16 bytes. With the use of some bitflags and by reducing the attcacheoff field size to a 16-bit type, we can halve the size of the struct. It's unlikely that caching the offsets for offsets larger than what will fit in a 16-bit int will help much as the tuple is very likely to have some non-fixed-width types anyway, the offsets of which we cannot cache. Shrinking this down to 8 bytes helps by accessing fewer cachelines when performing tuple deformation. The fields used there are all fully fledged fields, which don't require any bitmasking to extract the value of. It also helps to more efficiently calculate the address of a compact_attrs[] element in TupleDesc as the x86 LEA instruction can work with 8 byte offsets, which allows the element address to be calculated from the TupleDesc's address in a single instruction using LEA's concurrent shift and add. Author: David Rowley <dgrowleyml@gmail.com> Reviewed-by: Andres Freund <andres@anarazel.de> Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de> Discussion: https://postgr.es/m/CAApHDvodSVBj3ypOYbYUCJX%2BNWL%3DVZs63RNBQ_FxB_F%2B6QXF-A%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/.