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Add SQL function CASEFOLD().

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Useful for caseless matching. Similar to LOWER(), but avoids edge-case
problems with using LOWER() for caseless matching.

For collations that support it, CASEFOLD() handles characters with
more than two case variations or multi-character case variations. Some
characters may fold to uppercase. The results of case folding are also
more stable across Unicode versions than LOWER() or UPPER().

Discussion: https://postgr.es/m/a1886ddfcd8f60cb3e905c93009b646b4cfb74c5.camel%40j-davis.com
Reviewed-by: Ian Lawrence Barwick
This commit is contained in:
Jeff Davis
2025-01-24 14:56:22 -08:00
parent f15538cd27
commit bfc5992069
14 changed files with 278 additions and 3 deletions
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5
src/test/regress/sql/collate.icu.utf8.sql
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@@ -116,6 +116,11 @@ SELECT a, lower(x COLLATE "C"), lower(y COLLATE "C") FROM collate_test10;
SELECT a, x, y FROM collate_test10 ORDER BY lower(y), a;
SELECT lower('AbCd 123 #$% ıiIİ ẞ ß DŽDždž Σσς' COLLATE "en-x-icu");
SELECT casefold('AbCd 123 #$% ıiIİ ẞ ß DŽDždž Σσς' COLLATE "en-x-icu");
SELECT lower('AbCd 123 #$% ıiIİ ẞ ß DŽDždž Σσς' COLLATE "tr-x-icu");
SELECT casefold('AbCd 123 #$% ıiIİ ẞ ß DŽDždž Σσς' COLLATE "tr-x-icu");
-- LIKE/ILIKE
SELECT * FROM collate_test1 WHERE b LIKE 'abc';

6
src/test/regress/sql/collate.utf8.sql
View File

@@ -81,6 +81,9 @@ SELECT 'xAb' !~* '[c-d]' COLLATE PG_C_UTF8;
SELECT 'Δ' ~* '[γ-λ]' COLLATE PG_C_UTF8;
SELECT 'δ' ~* '[Γ-Λ]' COLLATE PG_C_UTF8; -- same as above with cases reversed
-- case folding
select casefold('AbCd 123 #$% ıiIİ ẞ ß DŽDždž Σσς' collate PG_C_UTF8);
--
-- Test PG_UNICODE_FAST
--
@@ -140,3 +143,6 @@ SELECT 'xAb' ~* '[W-Y]' COLLATE PG_UNICODE_FAST;
SELECT 'xAb' !~* '[c-d]' COLLATE PG_UNICODE_FAST;
SELECT 'Δ' ~* '[γ-λ]' COLLATE PG_UNICODE_FAST;
SELECT 'δ' ~* '[Γ-Λ]' COLLATE PG_UNICODE_FAST; -- same as above with cases reversed
-- case folding
select casefold('AbCd 123 #$% ıiIİ ẞ ß DŽDždž Σσς' collate PG_UNICODE_FAST);