Add IF NOT EXISTS for CREATE SERVER and CREATE USER MAPPING

There is still some inconsistency with the error messages surrounding
foreign servers. Some use the word "foreign" and some don't. My
inclination is to remove all such uses of "foreign" on the basis that
the  CREATE/ALTER/DROP SERVER commands don't use the word. However, that
is left for another day. In this patch I have kept to the existing usage
in the affected commands, which omits "foreign".

Anastasia Lubennikova, reviewed by Arthur Zakirov and Ashtosh Bapat.

Discussion: http://postgr.es/m/7c2ab9b8-388a-1ce0-23a3-7acf2a0ed3c6@postgrespro.ru

2 files changed, 26 insertions, 2 deletions

diff --git a/doc/src/sgml/ref/create_server.sgml b/doc/src/sgml/ref/create_server.sgml
index 734c6c9fe81..7318481487f 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/doc/src/sgml/ref/create_user_mapping.sgml b/doc/src/sgml/ref/create_user_mapping.sgml
index 44fe302fb5c..1c44679a985 100644
--- a/doc/src/sgml/ref/create_user_mapping.sgml
+++ b/doc/src/sgml/ref/create_user_mapping.sgml
@@ -21,7 +21,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-CREATE USER MAPPING FOR { <replaceable class="parameter">user_name</replaceable> | USER | CURRENT_USER | PUBLIC }
+CREATE USER MAPPING [IF NOT EXISTS] FOR { <replaceable class="parameter">user_name</replaceable> | USER | CURRENT_USER | PUBLIC }
     SERVER <replaceable class="parameter">server_name</replaceable>
     [ OPTIONS ( <replaceable class="PARAMETER">option</replaceable> '<replaceable class="PARAMETER">value</replaceable>' [ , ... ] ) ]
 </synopsis>
@@ -50,6 +50,18 @@ CREATE USER MAPPING FOR { <replaceable class="parameter">user_name</replaceable>
   <title>Parameters</title>
 
   <variablelist>
+  <varlistentry>
+    <term><literal>IF NOT EXISTS</></term>
+    <listitem>
+     <para>
+      Do not throw an error if a mapping of the given user to the given foreign
+      server already exists. A notice is issued in this case.  Note that there
+      is no guarantee that the existing user mapping is anything like the one
+      that would have been created.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><replaceable class="parameter">user_name</replaceable></term>
     <listitem>