Here is a patch to complete the implementation of CREATE COLLATION IF
NOT EXISTS. The meat of this was already implemented for
pg_import_system_collations; this just exposes it in the SQL command.
If we go ahead with ICU, then creating collations by hand will become
more common, so this could be useful in practice.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>From aa6f7563b0893961bbc5d82c8496c2bbea990f3c Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pete...@gmx.net>
Date: Wed, 8 Feb 2017 22:51:09 -0500
Subject: [PATCH] Add CREATE COLLATION IF NOT EXISTS clause
The core of the functionality was already implemented when
pg_import_system_collations was added. This just exposes it as an
option in the SQL command.
---
doc/src/sgml/ref/create_collation.sgml | 15 +++++++++++++--
src/backend/commands/collationcmds.c | 4 ++--
src/backend/nodes/copyfuncs.c | 1 +
src/backend/nodes/equalfuncs.c | 1 +
src/backend/parser/gram.y | 20 ++++++++++++++++++++
src/backend/tcop/utility.c | 3 ++-
src/include/commands/collationcmds.h | 2 +-
src/include/nodes/parsenodes.h | 1 +
src/test/regress/expected/collate.linux.utf8.out | 4 ++++
src/test/regress/sql/collate.linux.utf8.sql | 2 ++
10 files changed, 47 insertions(+), 6 deletions(-)
diff --git a/doc/src/sgml/ref/create_collation.sgml b/doc/src/sgml/ref/create_collation.sgml
index d757cdfb43..c09e5bd6d4 100644
--- a/doc/src/sgml/ref/create_collation.sgml
+++ b/doc/src/sgml/ref/create_collation.sgml
@@ -18,12 +18,12 @@
<refsynopsisdiv>
<synopsis>
-CREATE COLLATION <replaceable>name</replaceable> (
+CREATE COLLATION [ IF NOT EXISTS ] <replaceable>name</replaceable> (
[ LOCALE = <replaceable>locale</replaceable>, ]
[ LC_COLLATE = <replaceable>lc_collate</replaceable>, ]
[ LC_CTYPE = <replaceable>lc_ctype</replaceable> ]
)
-CREATE COLLATION <replaceable>name</replaceable> FROM <replaceable>existing_collation</replaceable>
+CREATE COLLATION [ IF NOT EXISTS ] <replaceable>name</replaceable> FROM <replaceable>existing_collation</replaceable>
</synopsis>
</refsynopsisdiv>
@@ -48,6 +48,17 @@ <title>Parameters</title>
<variablelist>
<varlistentry>
+ <term><literal>IF NOT EXISTS</literal></term>
+ <listitem>
+ <para>
+ Do not throw an error if a collation with the same name already exists.
+ A notice is issued in this case. Note that there is no guarantee that
+ the existing collation is anything like the one that would have been created.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
<term><replaceable>name</replaceable></term>
<listitem>
diff --git a/src/backend/commands/collationcmds.c b/src/backend/commands/collationcmds.c
index e165d4b2a6..919cfc6a06 100644
--- a/src/backend/commands/collationcmds.c
+++ b/src/backend/commands/collationcmds.c
@@ -37,7 +37,7 @@
* CREATE COLLATION
*/
ObjectAddress
-DefineCollation(ParseState *pstate, List *names, List *parameters)
+DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_exists)
{
char *collName;
Oid collNamespace;
@@ -137,7 +137,7 @@ DefineCollation(ParseState *pstate, List *names, List *parameters)
GetDatabaseEncoding(),
collcollate,
collctype,
- false);
+ if_not_exists);
if (!OidIsValid(newoid))
return InvalidObjectAddress;
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 30d733e57a..ab96d71a8f 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -3104,6 +3104,7 @@ _copyDefineStmt(const DefineStmt *from)
COPY_NODE_FIELD(defnames);
COPY_NODE_FIELD(args);
COPY_NODE_FIELD(definition);
+ COPY_SCALAR_FIELD(if_not_exists);
return newnode;
}
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 55c73b7292..94789feb08 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1210,6 +1210,7 @@ _equalDefineStmt(const DefineStmt *a, const DefineStmt *b)
COMPARE_NODE_FIELD(defnames);
COMPARE_NODE_FIELD(args);
COMPARE_NODE_FIELD(definition);
+ COMPARE_SCALAR_FIELD(if_not_exists);
return true;
}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index cf97be512d..7c025f247d 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -5606,6 +5606,16 @@ DefineStmt:
n->definition = $4;
$$ = (Node *)n;
}
+ | CREATE COLLATION IF_P NOT EXISTS any_name definition
+ {
+ DefineStmt *n = makeNode(DefineStmt);
+ n->kind = OBJECT_COLLATION;
+ n->args = NIL;
+ n->defnames = $6;
+ n->definition = $7;
+ n->if_not_exists = true;
+ $$ = (Node *)n;
+ }
| CREATE COLLATION any_name FROM any_name
{
DefineStmt *n = makeNode(DefineStmt);
@@ -5615,6 +5625,16 @@ DefineStmt:
n->definition = list_make1(makeDefElem("from", (Node *) $5, @5));
$$ = (Node *)n;
}
+ | CREATE COLLATION IF_P NOT EXISTS any_name FROM any_name
+ {
+ DefineStmt *n = makeNode(DefineStmt);
+ n->kind = OBJECT_COLLATION;
+ n->args = NIL;
+ n->defnames = $6;
+ n->definition = list_make1(makeDefElem("from", (Node *) $8, @8));
+ n->if_not_exists = true;
+ $$ = (Node *)n;
+ }
;
definition: '(' def_list ')' { $$ = $2; }
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 5d3be38bf5..3bc0ae5e7e 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -1271,7 +1271,8 @@ ProcessUtilitySlow(ParseState *pstate,
Assert(stmt->args == NIL);
address = DefineCollation(pstate,
stmt->defnames,
- stmt->definition);
+ stmt->definition,
+ stmt->if_not_exists);
break;
default:
elog(ERROR, "unrecognized define stmt type: %d",
diff --git a/src/include/commands/collationcmds.h b/src/include/commands/collationcmds.h
index 699ce2f9ee..3b2fcb8271 100644
--- a/src/include/commands/collationcmds.h
+++ b/src/include/commands/collationcmds.h
@@ -18,7 +18,7 @@
#include "catalog/objectaddress.h"
#include "nodes/parsenodes.h"
-extern ObjectAddress DefineCollation(ParseState *pstate, List *names, List *parameters);
+extern ObjectAddress DefineCollation(ParseState *pstate, List *names, List *parameters, bool if_not_exists);
extern void IsThereCollationInNamespace(const char *collname, Oid nspOid);
#endif /* COLLATIONCMDS_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 07a8436143..5afc3ebea0 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2380,6 +2380,7 @@ typedef struct DefineStmt
List *defnames; /* qualified name (list of Value strings) */
List *args; /* a list of TypeName (if needed) */
List *definition; /* a list of DefElem */
+ bool if_not_exists; /* just do nothing if it already exists? */
} DefineStmt;
/* ----------------------
diff --git a/src/test/regress/expected/collate.linux.utf8.out b/src/test/regress/expected/collate.linux.utf8.out
index 286c972fbb..293e78641e 100644
--- a/src/test/regress/expected/collate.linux.utf8.out
+++ b/src/test/regress/expected/collate.linux.utf8.out
@@ -963,6 +963,10 @@ END
$$;
CREATE COLLATION test0 FROM "C"; -- fail, duplicate name
ERROR: collation "test0" for encoding "UTF8" already exists
+CREATE COLLATION IF NOT EXISTS test0 FROM "C"; -- ok, skipped
+NOTICE: collation "test0" for encoding "UTF8" already exists, skipping
+CREATE COLLATION IF NOT EXISTS test0 (locale = 'foo'); -- ok, skipped
+NOTICE: collation "test0" for encoding "UTF8" already exists, skipping
do $$
BEGIN
EXECUTE 'CREATE COLLATION test1 (lc_collate = ' ||
diff --git a/src/test/regress/sql/collate.linux.utf8.sql b/src/test/regress/sql/collate.linux.utf8.sql
index 3b7cc6cf2b..c349cbde2b 100644
--- a/src/test/regress/sql/collate.linux.utf8.sql
+++ b/src/test/regress/sql/collate.linux.utf8.sql
@@ -325,6 +325,8 @@ CREATE SCHEMA test_schema;
END
$$;
CREATE COLLATION test0 FROM "C"; -- fail, duplicate name
+CREATE COLLATION IF NOT EXISTS test0 FROM "C"; -- ok, skipped
+CREATE COLLATION IF NOT EXISTS test0 (locale = 'foo'); -- ok, skipped
do $$
BEGIN
EXECUTE 'CREATE COLLATION test1 (lc_collate = ' ||
--
2.11.1
--
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