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Thomas Munro a0dc827112 Simplify replacement code for preadv and pwritev. 
preadv() and pwritev() are not standardized by POSIX, but appeared in
NetBSD in 1999 and were adopted by at least OpenBSD, FreeBSD,
DragonFlyBSD, Linux, AIX, illumos and macOS.  We don't use them much
yet, but an active proposal uses them heavily.

In 15, we had two replacement implementations for other OSes: one based
on lseek() + -v function if available for true vector I/O, and the other
based on a loop over p- function.

The former would be an obstacle to hypothetical future multi-threaded
code sharing file descriptors, while the latter would not, since commit
cf112c12.  Furthermore, the number of targeted systems that could
benefit from the former's potential upside has dwindled to just one
niche OS, since macOS added the functions and we de-supported HP-UX.
That doesn't seem like a good trade-off.

Therefore, drop the lseek()-based variant, and also the pg_ prefix now
that the file position portability hazard is gone.

At the time of writing, the only systems in our build farm that lack
native preadv/pwritev and thus use fallback code are:

 * Solaris (but not illumos)
 * macOS before release 11.0
 * Windows

With this commit, the above systems will now use the *same* fallback
code, the version that loops over pread()/pwrite().  Windows already
used that (though a later proposal may include true vector I/O for
Windows), so this decision really only affects Solaris, until it gets
around to adding these system calls.

Also remove some useless includes while here.

Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com
2022-08-05 14:04:02 +12:00
config Unify DLSUFFIX on Darwin 2022-07-06 07:41:33 +02:00
contrib Remove dead pread and pwrite replacement code. 2022-08-05 09:49:21 +12:00
doc Remove configure probes for symlink/readlink, and dead code. 2022-08-05 09:22:56 +12:00
src Simplify replacement code for preadv and pwritev. 2022-08-05 14:04:02 +12:00
.cirrus.yml ci: remove minor version from freebsd image name 2022-07-31 18:51:47 -07:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add .editorconfig 2019-12-18 09:13:13 +01:00
.git-blame-ignore-revs Add another old commit to git-blame-ignore-revs. 2022-08-03 09:28:27 -07:00
.gitattributes Remove trailing whitespace from *.sgml files. 2022-04-20 11:04:49 -04:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
aclocal.m4 Probe $PROVE not $PERL while checking for modules needed by TAP tests. 2021-11-22 12:54:52 -05:00
configure Simplify replacement code for preadv and pwritev. 2022-08-05 14:04:02 +12:00
configure.ac Simplify replacement code for preadv and pwritev. 2022-08-05 14:04:02 +12:00
COPYRIGHT Update copyright for 2022 2022-01-07 19:04:57 -05:00
GNUmakefile.in Run tests of libpq on installcheck-world, checkprep and check-world 2022-06-03 13:15:20 +09:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Dynamically find correct installation docs in Makefile. 2022-01-19 14:48:25 +01:00
README Canonicalize some URLs 2020-02-10 20:47:50 +01:00
README.git Canonicalize some URLs 2020-02-10 20:47:50 +01:00

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/.