Add smallserial pseudotype.

This is just like serial and bigserial, except it generates an int2
column rather than int4 or int8.

Mike Pultz, reviewed by Brar Piening and Josh Kupershmidt

doc/src/sgml/datatype.sgml

@@ -198,6 +198,12 @@
        <entry>signed two-byte integer</entry>
       </row>
 
+      <row>
+       <entry><type>smallserial</type></entry>
+       <entry><type>serial2</type></entry>
+       <entry>autoincrementing two-byte integer</entry>
+      </row>
+
       <row>
        <entry><type>serial</type></entry>
        <entry><type>serial4</type></entry>
@@ -368,6 +374,13 @@
         <entry>15 decimal digits precision</entry>
        </row>
 
+       <row>
+        <entry><type>smallserial</type></entry>
+        <entry>2 bytes</entry>
+        <entry>small autoincrementing integer</entry>
+        <entry>1 to 32767</entry>
+       </row>
+
        <row>
         <entry><type>serial</></entry>
         <entry>4 bytes</entry>
@@ -742,6 +755,10 @@ NUMERIC
    <sect2 id="datatype-serial">
     <title>Serial Types</title>
 
+    <indexterm zone="datatype-serial">
+     <primary>smallserial</primary>
+    </indexterm>
+
     <indexterm zone="datatype-serial">
      <primary>serial</primary>
     </indexterm>
@@ -750,6 +767,10 @@ NUMERIC
      <primary>bigserial</primary>
     </indexterm>
 
+    <indexterm zone="datatype-serial">
+     <primary>serial2</primary>
+    </indexterm>
+
     <indexterm zone="datatype-serial">
      <primary>serial4</primary>
     </indexterm>
@@ -769,8 +790,8 @@ NUMERIC
     </indexterm>
 
     <para>
-     The data types <type>serial</type> and <type>bigserial</type>
-     are not true types, but merely
+     The data types <type>smallserial</type>, <type>serial</type> and 
+     <type>bigserial</type> are not true types, but merely
      a notational convenience for creating unique identifier columns
      (similar to the <literal>AUTO_INCREMENT</literal> property
      supported by some other databases). In the current
@@ -828,7 +849,9 @@ ALTER SEQUENCE <replaceable class="parameter">tablename</replaceable>_<replaceab
      the same way, except that they create a <type>bigint</type>
      column.  <type>bigserial</type> should be used if you anticipate
      the use of more than 2<superscript>31</> identifiers over the
-     lifetime of the table.
+     lifetime of the table. The type names <type>smallserial</type> and
+     <type>serial2</type> also work the same way, execpt that they
+     create a <type>smallint</type> column.
     </para>
 
     <para>

doc/src/sgml/ecpg.sgml

@@ -844,6 +844,11 @@ do
        <entry><type>double</type></entry>
       </row>
 
+      <row>
+       <entry><type>smallserial</type></entry>
+       <entry><type>short</type></entry>
+      </row>
+
       <row>
        <entry><type>serial</type></entry>
        <entry><type>int</type></entry>

doc/src/sgml/func.sgml

@@ -13366,7 +13366,7 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
       <row>
        <entry><literal><function>pg_get_serial_sequence(<parameter>table_name</parameter>, <parameter>column_name</parameter>)</function></literal></entry>
        <entry><type>text</type></entry>
-       <entry>get name of the sequence that a <type>serial</type> or <type>bigserial</type> column
+       <entry>get name of the sequence that a <type>serial</type>, <type>smallserial</type> or <type>bigserial</type> column
        uses</entry>
       </row>
       <row>

src/backend/parser/parse_utilcmd.c

@@ -307,7 +307,14 @@ transformColumnDefinition(CreateStmtContext *cxt, ColumnDef *column)
 	{
 		char	   *typname = strVal(linitial(column->typeName->names));
 
-		if (strcmp(typname, "serial") == 0 ||
+		if (strcmp(typname, "smallserial") == 0 ||
+			strcmp(typname, "serial2") == 0)
+		{
+			is_serial = true;
+			column->typeName->names = NIL;
+			column->typeName->typeOid = INT2OID;
+		}
+		else if (strcmp(typname, "serial") == 0 ||
 			strcmp(typname, "serial4") == 0)
 		{
 			is_serial = true;