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Allow creation of C/POSIX collations without depending on libc behavior. 

Most of our collations code has special handling for the locale names
"C" and "POSIX", allowing those collations to be used whether or not
the system libraries think those locale names are valid, or indeed
whether said libraries even have any locale support.  But we missed
handling things that way in CREATE COLLATION.  This meant you couldn't
clone the C/POSIX collations, nor explicitly define a new collation
using those locale names, unless the libraries allow it.  That's pretty
pointless, as well as being a violation of pg_newlocale_from_collation's
API specification.

The practical effect of this change is quite limited: it allows creating
such collations even on platforms that don't HAVE_LOCALE_T, and it allows
making "POSIX" collation objects on Windows, which before this would only
let you make "C" collation objects.  Hence, even though this is a bug fix
IMO, it doesn't seem worth the trouble to back-patch.

In passing, suppress the DROP CASCADE detail messages at the end of the
collation regression test.  I'm surprised we've never been bit by
message ordering issues there.

Per report from Murtuza Zabuawala.

Discussion: https://postgr.es/m/CAKKotZS-wcDcofXDCH=sidiuajE+nqHn2CGjLLX78anyDmi3gQ@mail.gmail.com
This commit is contained in:
Tom Lane 2017-08-01 13:51:05 -04:00
parent b21c569cea
commit f97256570f
3 changed files with 33 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
src/backend/commands/collationcmds.c
View File

@ -214,11 +214,15 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
if (!OidIsValid(newoid))
return InvalidObjectAddress;
ObjectAddressSet(address, CollationRelationId, newoid);
/* check that the locales can be loaded */
/*
* Check that the locales can be loaded. NB: pg_newlocale_from_collation
* is only supposed to be called on non-C-equivalent locales.
*/
CommandCounterIncrement();
(void) pg_newlocale_from_collation(newoid);
if (!lc_collate_is_c(newoid) || !lc_ctype_is_c(newoid))
(void) pg_newlocale_from_collation(newoid);
ObjectAddressSet(address, CollationRelationId, newoid);
return address;
}

29
src/test/regress/expected/collate.out
View File

@ -622,6 +622,17 @@ EXPLAIN (COSTS OFF)
-> Seq Scan on collate_test10
(3 rows)
-- CREATE/DROP COLLATION
CREATE COLLATION mycoll1 FROM "C";
CREATE COLLATION mycoll2 ( LC_COLLATE = "POSIX", LC_CTYPE = "POSIX" );
CREATE COLLATION mycoll3 FROM "default"; -- intentionally unsupported
ERROR: collation "default" cannot be copied
DROP COLLATION mycoll1;
CREATE TABLE collate_test23 (f1 text collate mycoll2);
DROP COLLATION mycoll2; -- fail
ERROR: cannot drop collation mycoll2 because other objects depend on it
DETAIL: table collate_test23 column f1 depends on collation mycoll2
HINT: Use DROP ... CASCADE to drop the dependent objects too.
-- 9.1 bug with useless COLLATE in an expression subject to length coercion
CREATE TEMP TABLE vctable (f1 varchar(25));
INSERT INTO vctable VALUES ('foo' COLLATE "C");
@ -650,20 +661,6 @@ SELECT collation for ((SELECT b FROM collate_test1 LIMIT 1));
-- trying to run any platform-specific collation tests later, so we
-- must get rid of them.
--
\set VERBOSITY terse
DROP SCHEMA collate_tests CASCADE;
NOTICE: drop cascades to 15 other objects
DETAIL: drop cascades to table collate_test1
drop cascades to table collate_test_like
drop cascades to table collate_test2
drop cascades to type testdomain_p
drop cascades to table collate_test4
drop cascades to table collate_test5
drop cascades to table collate_test10
drop cascades to view collview1
drop cascades to view collview2
drop cascades to view collview3
drop cascades to type testdomain
drop cascades to function dup(anyelement)
drop cascades to table collate_test20
drop cascades to table collate_test21
drop cascades to table collate_test22
NOTICE: drop cascades to 17 other objects

12
src/test/regress/sql/collate.sql
View File

@ -229,6 +229,17 @@ EXPLAIN (COSTS OFF)
SELECT * FROM collate_test10 ORDER BY x DESC, y COLLATE "C" ASC NULLS FIRST;
-- CREATE/DROP COLLATION
CREATE COLLATION mycoll1 FROM "C";
CREATE COLLATION mycoll2 ( LC_COLLATE = "POSIX", LC_CTYPE = "POSIX" );
CREATE COLLATION mycoll3 FROM "default"; -- intentionally unsupported
DROP COLLATION mycoll1;
CREATE TABLE collate_test23 (f1 text collate mycoll2);
DROP COLLATION mycoll2; -- fail
-- 9.1 bug with useless COLLATE in an expression subject to length coercion
CREATE TEMP TABLE vctable (f1 varchar(25));
@ -246,4 +257,5 @@ SELECT collation for ((SELECT b FROM collate_test1 LIMIT 1));
-- trying to run any platform-specific collation tests later, so we
-- must get rid of them.
--
\set VERBOSITY terse
DROP SCHEMA collate_tests CASCADE;