create_foreign_server_if_not_exists_3.0.patch

Idiff --git a/doc/src/sgml/ref/create_server.sgml b/doc/src/sgml/ref/create_server.sgml
index 734c6c9..7318481 100644
--- a/doc/src/sgml/ref/create_server.sgml
+++ b/doc/src/sgml/ref/create_server.sgml
@@ -21,7 +21,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-CREATE SERVER <replaceable class="parameter">server_name</replaceable> [ TYPE '<replaceable class="parameter">server_type</replaceable>' ] [ VERSION '<replaceable class="parameter">server_version</replaceable>' ]
+CREATE SERVER [IF NOT EXISTS] <replaceable class="parameter">server_name</replaceable> [ TYPE '<replaceable class="parameter">server_type</replaceable>' ] [ VERSION '<replaceable class="parameter">server_version</replaceable>' ]
     FOREIGN DATA WRAPPER <replaceable class="parameter">fdw_name</replaceable>
     [ OPTIONS ( <replaceable class="PARAMETER">option</replaceable> '<replaceable class="PARAMETER">value</replaceable>' [, ... ] ) ]
 </synopsis>
@@ -56,6 +56,18 @@ CREATE SERVER <replaceable class="parameter">server_name</replaceable> [ TYPE '<
   <title>Parameters</title>
 
   <variablelist>
+  <varlistentry>
+    <term><literal>IF NOT EXISTS</></term>
+    <listitem>
+     <para>
+      Do not throw an error if a server with the same name already exists.
+      A notice is issued in this case.  Note that there is no guarantee that
+      the existing server is anything like the one that would have been
+      created.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><replaceable class="parameter">server_name</replaceable></term>
     <listitem>
diff --git a/src/backend/commands/foreigncmds.c b/src/backend/commands/foreigncmds.c
index d5d40e6..41b2c01 100644
--- a/src/backend/commands/foreigncmds.c
+++ b/src/backend/commands/foreigncmds.c
@@ -879,12 +879,25 @@ CreateForeignServer(CreateForeignServerStmt *stmt)
 
 	/*
 	 * Check that there is no other foreign server by this name.
+	 * Do nothing if IF NOT EXISTS was enforced.
 	 */
 	if (GetForeignServerByName(stmt->servername, true) != NULL)
-		ereport(ERROR,
-				(errcode(ERRCODE_DUPLICATE_OBJECT),
-				 errmsg("server \"%s\" already exists",
-						stmt->servername)));
+	{
+		if (stmt->if_not_exists)
+		{
+			ereport(NOTICE,
+					(errcode(ERRCODE_DUPLICATE_OBJECT),
+					 errmsg("foreign server \"%s\" already exists, skipping",
+							stmt->servername)));
+			heap_close(rel, RowExclusiveLock);
+			return InvalidObjectAddress;
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_DUPLICATE_OBJECT),
+					 errmsg("foreign server \"%s\" already exists",
+							stmt->servername)));
+	}
 
 	/*
 	 * Check that the FDW exists and that we have USAGE on it. Also get the
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index e7acc2d..da67b51 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -4621,6 +4621,19 @@ CreateForeignServerStmt: CREATE SERVER name opt_type opt_foreign_server_version
 					n->version = $5;
 					n->fdwname = $9;
 					n->options = $10;
+					n->if_not_exists = false;
+					$$ = (Node *) n;
+				}
+				| CREATE SERVER IF_P NOT EXISTS name opt_type opt_foreign_server_version
+						 FOREIGN DATA_P WRAPPER name create_generic_options
+				{
+					CreateForeignServerStmt *n = makeNode(CreateForeignServerStmt);
+					n->servername = $6;
+					n->servertype = $7;
+					n->version = $8;
+					n->fdwname = $12;
+					n->options = $13;
+					n->if_not_exists = true;
 					$$ = (Node *) n;
 				}
 		;
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index a44d217..804436b 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2151,6 +2151,7 @@ typedef struct CreateForeignServerStmt
 	char	   *servertype;		/* optional server type */
 	char	   *version;		/* optional server version */
 	char	   *fdwname;		/* FDW name */
+	bool		if_not_exists;	/* just do nothing if it already exists? */
 	List	   *options;		/* generic options to server */
 } CreateForeignServerStmt;
 
diff --git a/src/test/regress/expected/foreign_data.out b/src/test/regress/expected/foreign_data.out
index a0f969f..4d39e37 100644
--- a/src/test/regress/expected/foreign_data.out
+++ b/src/test/regress/expected/foreign_data.out
@@ -283,7 +283,9 @@ ERROR:  foreign-data wrapper "foo" does not exist
 CREATE FOREIGN DATA WRAPPER foo OPTIONS ("test wrapper" 'true');
 CREATE SERVER s1 FOREIGN DATA WRAPPER foo;
 CREATE SERVER s1 FOREIGN DATA WRAPPER foo;                  -- ERROR
-ERROR:  server "s1" already exists
+ERROR:  foreign server "s1" already exists
+CREATE SERVER IF NOT EXISTS s1 FOREIGN DATA WRAPPER foo;	-- No ERROR, just NOTICE
+NOTICE:  foreign server "s1" already exists, skipping
 CREATE SERVER s2 FOREIGN DATA WRAPPER foo OPTIONS (host 'a', dbname 'b');
 CREATE SERVER s3 TYPE 'oracle' FOREIGN DATA WRAPPER foo;
 CREATE SERVER s4 TYPE 'oracle' FOREIGN DATA WRAPPER foo OPTIONS (host 'a', dbname 'b');
diff --git a/src/test/regress/sql/foreign_data.sql b/src/test/regress/sql/foreign_data.sql
index c13d5ff..c1d688f 100644
--- a/src/test/regress/sql/foreign_data.sql
+++ b/src/test/regress/sql/foreign_data.sql
@@ -121,6 +121,7 @@ CREATE SERVER s1 FOREIGN DATA WRAPPER foo;                  -- ERROR
 CREATE FOREIGN DATA WRAPPER foo OPTIONS ("test wrapper" 'true');
 CREATE SERVER s1 FOREIGN DATA WRAPPER foo;
 CREATE SERVER s1 FOREIGN DATA WRAPPER foo;                  -- ERROR
+CREATE SERVER IF NOT EXISTS s1 FOREIGN DATA WRAPPER foo;	-- No ERROR, just NOTICE
 CREATE SERVER s2 FOREIGN DATA WRAPPER foo OPTIONS (host 'a', dbname 'b');
 CREATE SERVER s3 TYPE 'oracle' FOREIGN DATA WRAPPER foo;
 CREATE SERVER s4 TYPE 'oracle' FOREIGN DATA WRAPPER foo OPTIONS (host 'a', dbname 'b');