Re: Optimization for lower(), upper(), casefold() functions.

Heikki Linnakangas <hlinnaka@iki.fi>

From: Heikki Linnakangas <hlinnaka@iki.fi>

To: Jeff Davis <pgsql@j-davis.com>, Alexander Borisov <lex.borisov@gmail.com>, pgsql-hackers@postgresql.org

Date: 2025-03-14T11:16:42Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Fix headerscheck warning.
- 549ea06e4217 18.0 landed
Optimization for lower(), upper(), casefold() functions.
- 27bdec06841d 18.0 landed
Refactor convert_case() to prepare for optimizations.
- d3b2e5e1ab5c 18.0 landed
Improve performance of Unicode {de,re}composition in the backend
- 783f0cc64dcc 14.0 cited

Attachments

0001-minor-fixes-in-the-perl-script.patch (text/x-patch) patch 0001
0002-use-decimal-for-case_map_special-indexes.patch (text/x-patch) patch 0002
0003-use-better-comment-for-the-0th-reserved-entry-in-the.patch (text/x-patch) patch 0003

On 14/03/2025 05:43, Jeff Davis wrote:
> On Wed, 2025-03-12 at 23:39 +0300, Alexander Borisov wrote:
>> v5 attached.
> 
> Attached v6j.
> 
> * marked arrays as "static const" rather than just "static"
> * ran pgindent
> * changed data types where appropriate (uint32->pg_wchar)
> * modified perl code so that it produces code that's already pgindented
> * cleanup of perl code, removing unnecessary subroutines and variables
> * added a few comments
> * ran pgperltidy
> 
> Some of the perl code working with ranges still needs further cleanup
> and explanation, though.
> 
> Also, I ran some of my own simple tests (mostly ASCII) and it showed
> over 10% speedup. That combined with the smaller table sizes makes this
> well worth it.

Looks good overall.

> static const pg_wchar case_map_lower[1677] =
> {
> 	0x000000,					/* U+000000 */
> 	0x000000,					/* U+000000 */
> 	0x000001,					/* U+000001 */
> 	0x000002,					/* U+000002 */

The duplicated 0x000000 looks wrong. I understand that the 0'th entry is 
reserved, and the actual codepoints start at index 1, but the /* 
U+000000 */ comment on the 0'th entry is misleading.

> static const uint8 case_map_special[1677] =
> {
> 	0x000000,					/* U+000000 */
> 	0x000000,					/* U+000000 */
> 	...

0x000000 implies an 24-bit integer, but these are uint8's. Let's use 
plain base-10 decimals here rather than hex, like in 'case_map'.

Attached are fixes for those and some other minor things.

-- 
Heikki Linnakangas
Neon (https://neon.tech)