v6-0004-Add-default_collation_provider-GUC.patch

From 2a857a2cb080dbc015c59b89acbb195ae7991a99 Mon Sep 17 00:00:00 2001
From: Jeff Davis <jeff@j-davis.com>
Date: Thu, 11 May 2023 12:54:31 -0700
Subject: [PATCH v6 4/5] Add default_collation_provider GUC.

Controls default collation provider for CREATE COLLATION. Does not
affect CREATE DATABASE, which gets its default from the template
database.
---
 doc/src/sgml/config.sgml                      | 17 +++++++++++++
 doc/src/sgml/ref/create_collation.sgml        | 15 ++++++++---
 src/backend/commands/collationcmds.c          |  8 +++++-
 src/backend/utils/misc/guc_tables.c           | 18 +++++++++++++
 src/backend/utils/misc/postgresql.conf.sample |  4 +++
 src/include/commands/collationcmds.h          |  2 ++
 .../regress/expected/collate.icu.utf8.out     | 25 +++++++++++++++++++
 src/test/regress/sql/collate.icu.utf8.sql     | 13 ++++++++++
 8 files changed, 97 insertions(+), 5 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 18ce06729b..58a1046340 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -9820,6 +9820,23 @@ SET XML OPTION { DOCUMENT | CONTENT };
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-default-collation-provider" xreflabel="default_collation_provider">
+      <term><varname>default_collation_provider</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>default_collation_provider</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Default collation provider for <command>CREATE
+        COLLATION</command>. Does not affect <command>CREATE
+        DATABASE</command>, which gets the default collation provider from the
+        template database. Valid values are <literal>icu</literal> and
+        <literal>libc</literal>. The default is <literal>libc</literal>.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-icu-validation-level" xreflabel="icu_validation_level">
       <term><varname>icu_validation_level</varname> (<type>enum</type>)
       <indexterm>
diff --git a/doc/src/sgml/ref/create_collation.sgml b/doc/src/sgml/ref/create_collation.sgml
index 1ac41831d8..c9b3e6e218 100644
--- a/doc/src/sgml/ref/create_collation.sgml
+++ b/doc/src/sgml/ref/create_collation.sgml
@@ -121,10 +121,17 @@ CREATE COLLATION [ IF NOT EXISTS ] <replaceable>name</replaceable> FROM <replace
       <para>
        Specifies the provider to use for locale services associated with this
        collation.  Possible values are <literal>none</literal>,
-       <literal>icu</literal><indexterm><primary>ICU</primary></indexterm>
-       (if the server was built with ICU support) or <literal>libc</literal>.
-       <literal>libc</literal> is the default.  See <xref
-       linkend="locale-providers"/> for details.
+       <literal>icu</literal><indexterm><primary>ICU</primary></indexterm> (if
+       the server was built with ICU support) or <literal>libc</literal>.  See
+       <xref linkend="locale-providers"/> for details.
+      </para>
+      <para>
+       If <replaceable>provider</replaceable> is not specified, and
+       <replaceable>lc_collate</replaceable> or
+       <replaceable>lc_ctype</replaceable> is specified, the
+       <literal>libc</literal> provider is used. Otherwise, the default
+       provider is controlled by <xref
+       linkend="guc-default-collation-provider"/>.
       </para>
       <para>
        If the provider is <literal>icu</literal> and the locale is
diff --git a/src/backend/commands/collationcmds.c b/src/backend/commands/collationcmds.c
index 21615746f9..25e8d32fd9 100644
--- a/src/backend/commands/collationcmds.c
+++ b/src/backend/commands/collationcmds.c
@@ -47,6 +47,7 @@ typedef struct
 	int			enc;			/* encoding */
 } CollAliasData;
 
+int		default_collation_provider = (int) COLLPROVIDER_LIBC;
 
 /*
  * CREATE COLLATION
@@ -228,7 +229,12 @@ DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_e
 								collproviderstr)));
 		}
 		else
-			collprovider = COLLPROVIDER_LIBC;
+		{
+			if (lccollateEl || lcctypeEl)
+				collprovider = COLLPROVIDER_LIBC;
+			else
+				collprovider = (char) default_collation_provider;
+		}
 
 		if (collprovider == COLLPROVIDER_NONE
 			&& (localeEl || lccollateEl || lcctypeEl))
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 844781a7f5..901cfda819 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -35,8 +35,10 @@
 #include "access/xlogrecovery.h"
 #include "archive/archive_module.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_collation.h"
 #include "catalog/storage.h"
 #include "commands/async.h"
+#include "commands/collationcmds.h"
 #include "commands/tablespace.h"
 #include "commands/trigger.h"
 #include "commands/user.h"
@@ -166,6 +168,12 @@ static const struct config_enum_entry intervalstyle_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry collation_provider_options[] = {
+	{"icu", (int) 'i', false},
+	{"libc", (int) 'c', false},
+	{NULL, 0, false}
+};
+
 static const struct config_enum_entry icu_validation_level_options[] = {
 	{"disabled", -1, false},
 	{"debug5", DEBUG5, false},
@@ -4683,6 +4691,16 @@ struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"default_collation_provider", PGC_USERSET, CLIENT_CONN_LOCALE,
+		 gettext_noop("Default collation provider for CREATE COLLATION."),
+		 NULL
+		},
+		&default_collation_provider,
+		(int) COLLPROVIDER_LIBC, collation_provider_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"icu_validation_level", PGC_USERSET, CLIENT_CONN_LOCALE,
 		 gettext_noop("Log level for reporting invalid ICU locale strings."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index c8018da04a..c1f247378d 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -734,6 +734,10 @@
 #lc_numeric = 'C'			# locale for number formatting
 #lc_time = 'C'				# locale for time formatting
 
+#default_collation_provider = 'libc'	# default collation provider
+					# for CREATE COLLATION
+					# (none, icu, libc)
+
 #icu_validation_level = WARNING		# report ICU locale validation
 					# errors at the given level
 
diff --git a/src/include/commands/collationcmds.h b/src/include/commands/collationcmds.h
index b76c7b3dc3..f54389525d 100644
--- a/src/include/commands/collationcmds.h
+++ b/src/include/commands/collationcmds.h
@@ -18,6 +18,8 @@
 #include "catalog/objectaddress.h"
 #include "parser/parse_node.h"
 
+extern PGDLLIMPORT int default_collation_provider;
+
 extern ObjectAddress DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_exists);
 extern void IsThereCollationInNamespace(const char *collname, Oid nspOid);
 extern ObjectAddress AlterCollation(AlterCollationStmt *stmt);
diff --git a/src/test/regress/expected/collate.icu.utf8.out b/src/test/regress/expected/collate.icu.utf8.out
index cf1852c89d..ea96e27f45 100644
--- a/src/test/regress/expected/collate.icu.utf8.out
+++ b/src/test/regress/expected/collate.icu.utf8.out
@@ -1038,6 +1038,31 @@ RESET client_min_messages;
 -- uses "none" provider instead
 CREATE COLLATION testc (provider = icu, locale='C');
 NOTICE:  using locale provider "none" for ICU locale "C"
+SET default_collation_provider = 'libc';
+CREATE COLLATION def_libc (LOCALE = 'C');
+SELECT collname, collprovider FROM pg_collation WHERE collname='def_libc';
+ collname | collprovider 
+----------+--------------
+ def_libc | c
+(1 row)
+
+DROP COLLATION def_libc;
+SET default_collation_provider = 'icu';
+CREATE COLLATION def_icu (LOCALE = 'und');
+SELECT collname, collprovider FROM pg_collation WHERE collname='def_icu';
+ collname | collprovider 
+----------+--------------
+ def_icu  | i
+(1 row)
+
+CREATE COLLATION def_libc (LC_COLLATE = 'C', LC_CTYPE='C');
+SELECT collname, collprovider FROM pg_collation WHERE collname='def_libc';
+ collname | collprovider 
+----------+--------------
+ def_libc | c
+(1 row)
+
+RESET default_collation_provider;
 CREATE COLLATION test3 (provider = icu, lc_collate = 'en_US.utf8'); -- fail, needs "locale"
 ERROR:  parameter "locale" must be specified
 SET icu_validation_level = ERROR;
diff --git a/src/test/regress/sql/collate.icu.utf8.sql b/src/test/regress/sql/collate.icu.utf8.sql
index e59200df9a..ee607ca3a5 100644
--- a/src/test/regress/sql/collate.icu.utf8.sql
+++ b/src/test/regress/sql/collate.icu.utf8.sql
@@ -378,6 +378,19 @@ RESET client_min_messages;
 -- uses "none" provider instead
 CREATE COLLATION testc (provider = icu, locale='C');
 
+SET default_collation_provider = 'libc';
+CREATE COLLATION def_libc (LOCALE = 'C');
+SELECT collname, collprovider FROM pg_collation WHERE collname='def_libc';
+DROP COLLATION def_libc;
+
+SET default_collation_provider = 'icu';
+CREATE COLLATION def_icu (LOCALE = 'und');
+SELECT collname, collprovider FROM pg_collation WHERE collname='def_icu';
+CREATE COLLATION def_libc (LC_COLLATE = 'C', LC_CTYPE='C');
+SELECT collname, collprovider FROM pg_collation WHERE collname='def_libc';
+
+RESET default_collation_provider;
+
 CREATE COLLATION test3 (provider = icu, lc_collate = 'en_US.utf8'); -- fail, needs "locale"
 SET icu_validation_level = ERROR;
 CREATE COLLATION testx (provider = icu, locale = 'nonsense-nowhere'); -- fails
-- 
2.34.1