Introduce "builtin" collation provider.

New provider for collations, like "libc" or "icu", but without any
external dependency.

Initially, the only locale supported by the builtin provider is "C",
which is identical to the libc provider's "C" locale. The libc
provider's "C" locale has always been treated as a special case that
uses an internal implementation, without using libc at all -- so the
new builtin provider uses the same implementation.

The builtin provider's locale is independent of the server environment
variables LC_COLLATE and LC_CTYPE. Using the builtin provider, the
database collation locale can be "C" while LC_COLLATE and LC_CTYPE are
set to "en_US", which is impossible with the libc provider.

By offering a new builtin provider, it clarifies that the semantics of
a collation using this provider will never depend on libc, and makes
it easier to document the behavior.

Discussion: https://postgr.es/m/ab925f69-5f9d-f85e-b87c-bd2a44798659@joeconway.com
Discussion: https://postgr.es/m/dd9261f4-7a98-4565-93ec-336c1c110d90@manitou-mail.org
Discussion: https://postgr.es/m/ff4c2f2f9c8fc7ca27c1c24ae37ecaeaeaff6b53.camel%40j-davis.com
Reviewed-by: Daniel Vérité, Peter Eisentraut, Jeremy Schneider

3 files changed, 36 insertions, 13 deletions

diff --git a/src/test/icu/t/010_database.pl b/src/test/icu/t/010_database.pl
index 8a1fc12ec63..5f8ef168034 100644
--- a/src/test/icu/t/010_database.pl
+++ b/src/test/icu/t/010_database.pl
@@ -27,9 +27,8 @@ CREATE TABLE icu (def text, en text COLLATE "en-x-icu", upfirst text COLLATE upp
 INSERT INTO icu VALUES ('a', 'a', 'a'), ('b', 'b', 'b'), ('A', 'A', 'A'), ('B', 'B', 'B');
 });
 
-is( $node1->safe_psql('dbicu', q{SELECT icu_unicode_version() IS NOT NULL}),
-	qq(t),
-	'ICU unicode version defined');
+is($node1->safe_psql('dbicu', q{SELECT icu_unicode_version() IS NOT NULL}),
+	qq(t), 'ICU unicode version defined');
 
 is( $node1->safe_psql('dbicu', q{SELECT def FROM icu ORDER BY def}),
 	qq(A
@@ -63,14 +62,13 @@ is( $node1->psql(
 	0,
 	"C locale works for ICU");
 
-# Test that LOCALE works for ICU locales if LC_COLLATE and LC_CTYPE
-# are specified
-is( $node1->psql(
-		'postgres',
-		q{CREATE DATABASE dbicu2 LOCALE_PROVIDER icu LOCALE '@colStrength=primary'
-      LC_COLLATE='C' LC_CTYPE='C' TEMPLATE template0 ENCODING UTF8}
-	),
-	0,
-	"LOCALE works for ICU locales if LC_COLLATE and LC_CTYPE are specified");
+my ($ret, $stdout, $stderr) = $node1->psql('postgres',
+	q{CREATE DATABASE dbicu LOCALE_PROVIDER builtin LOCALE 'C' TEMPLATE dbicu}
+);
+isnt($ret, 0, "locale provider must match template: exit code not 0");
+like(
+	$stderr,
+	qr/ERROR:  new locale provider \(builtin\) does not match locale provider of the template database \(icu\)/,
+	"locale provider must match template: error message");
 
 done_testing();
diff --git a/src/test/regress/expected/collate.out b/src/test/regress/expected/collate.out
index 06495644852..593a6226376 100644
--- a/src/test/regress/expected/collate.out
+++ b/src/test/regress/expected/collate.out
@@ -650,6 +650,22 @@ EXPLAIN (COSTS OFF)
 (3 rows)
 
 -- CREATE/DROP COLLATION
+CREATE COLLATION builtin_c ( PROVIDER = builtin, LOCALE = "C" );
+SELECT b FROM collate_test1 ORDER BY b COLLATE builtin_c;
+  b  
+-----
+ ABD
+ Abc
+ abc
+ bbc
+(4 rows)
+
+CREATE COLLATION builtin2 ( PROVIDER = builtin ); -- fails
+ERROR:  parameter "locale" must be specified
+CREATE COLLATION builtin2 ( PROVIDER = builtin, LOCALE = "en_US" ); -- fails
+ERROR:  invalid locale name "en_US" for builtin provider
+CREATE COLLATION builtin2 ( PROVIDER = builtin, LC_CTYPE = "C", LC_COLLATE = "C" ); -- fails
+ERROR:  parameter "locale" must be specified
 CREATE COLLATION mycoll1 FROM "C";
 CREATE COLLATION mycoll2 ( LC_COLLATE = "POSIX", LC_CTYPE = "POSIX" );
 CREATE COLLATION mycoll3 FROM "default";  -- intentionally unsupported
@@ -754,7 +770,7 @@ DETAIL:  FROM cannot be specified together with any other options.
 -- must get rid of them.
 --
 DROP SCHEMA collate_tests CASCADE;
-NOTICE:  drop cascades to 19 other objects
+NOTICE:  drop cascades to 20 other objects
 DETAIL:  drop cascades to table collate_test1
 drop cascades to table collate_test_like
 drop cascades to table collate_test2
@@ -771,6 +787,7 @@ drop cascades to function dup(anyelement)
 drop cascades to table collate_test20
 drop cascades to table collate_test21
 drop cascades to table collate_test22
+drop cascades to collation builtin_c
 drop cascades to collation mycoll2
 drop cascades to table collate_test23
 drop cascades to view collate_on_int
diff --git a/src/test/regress/sql/collate.sql b/src/test/regress/sql/collate.sql
index c3d40fc1959..4b0e4472c3f 100644
--- a/src/test/regress/sql/collate.sql
+++ b/src/test/regress/sql/collate.sql
@@ -244,6 +244,14 @@ EXPLAIN (COSTS OFF)
 
 -- CREATE/DROP COLLATION
 
+CREATE COLLATION builtin_c ( PROVIDER = builtin, LOCALE = "C" );
+
+SELECT b FROM collate_test1 ORDER BY b COLLATE builtin_c;
+
+CREATE COLLATION builtin2 ( PROVIDER = builtin ); -- fails
+CREATE COLLATION builtin2 ( PROVIDER = builtin, LOCALE = "en_US" ); -- fails
+CREATE COLLATION builtin2 ( PROVIDER = builtin, LC_CTYPE = "C", LC_COLLATE = "C" ); -- fails
+
 CREATE COLLATION mycoll1 FROM "C";
 CREATE COLLATION mycoll2 ( LC_COLLATE = "POSIX", LC_CTYPE = "POSIX" );
 CREATE COLLATION mycoll3 FROM "default";  -- intentionally unsupported