Improve performance and reduce table sizes for case mapping.
The main case mapping table stores only 16-bit offsets, which can be
used to look up the mapped code point in any of the case tables (fold,
lower, upper, or title case). Simple case pairs point to the same
offsets.
Generate a function in generate-unicode_case_table.pl that consists of
a nested branches to test for specific codepoint ranges that determine
the offset in the main table.
Other approaches were considered, such as representing these ranges as
another structure (rather than branches in a generated function), or a
different approach such as a radix tree, or perfect hashing. The
author implemented and tested these alternatives and settled on the
generated branches.
Author: Alexander Borisov <lex.borisov@gmail.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Discussion: https://postgr.es/m/7cac7e66-9a3b-4e3f-a997-42aa0c401f80%40gmail.com
Run pgindent, pgperltidy, and reformat-dat-files.
The pgindent part of this is pretty small, consisting mainly of
fixing up self-inflicted formatting damage from patches that
hadn't bothered to add their new typedefs to typedefs.list.
In order to keep it from making anything worse, I manually added
a dozen or so typedefs that appeared in the existing typedefs.list
but not in the buildfarm's list. Perhaps we should formalize that,
or better find a way to get those typedefs into the automatic list.
pgperltidy is as opinionated as always, and reformat-dat-files too.
Implements Unicode simple case mapping, in which all code points map
to exactly one other code point unconditionally.
These tables are generated from UnicodeData.txt, which is already
being used by other infrastructure in src/common/unicode. The tables
are checked into the source tree, so they only need to be regenerated
when we update the Unicode version.
In preparation for the builtin collation provider, and possibly useful
for other callers.
Discussion: https://postgr.es/m/ff4c2f2f9c8fc7ca27c1c24ae37ecaeaeaff6b53.camel%40j-davis.com
Reviewed-by: Peter Eisentraut, Daniel Verite, Jeremy Schneider
