Reclassify DEFAULT as a column_constraint item in the CREATE TABLE syntax.

This is how it was documented originally, but several years ago somebody
decided that DEFAULT isn't a type of constraint.  Well, the grammar thinks
it is.  The documentation was wrong in two ways: it alleged that DEFAULT
had to appear before any other kind of constraint, and it alleged that you
can't prefix a DEFAULT clause with a "CONSTRAINT name" clause, when in fact
you can.  (The latter behavior probably isn't SQL-standard, but our grammar
has always allowed it.)

This patch responds to Fujii Masao's observation that the ALTER TABLE
documentation mistakenly implied that you couldn't include DEFAULT in
ALTER TABLE ADD COLUMN; though this isn't the way he proposed fixing it.

doc/src/sgml/ref/alter_table.sgml

@@ -32,7 +32,7 @@ ALTER TABLE <replaceable class="PARAMETER">name</replaceable>
 
 <phrase>where <replaceable class="PARAMETER">action</replaceable> is one of:</phrase>
 
-    ADD [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> <replaceable class="PARAMETER">type</replaceable> [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
+    ADD [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> <replaceable class="PARAMETER">data_type</replaceable> [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
     DROP [ COLUMN ] [ IF EXISTS ] <replaceable class="PARAMETER">column</replaceable> [ RESTRICT | CASCADE ]
     ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> [ SET DATA ] TYPE <replaceable class="PARAMETER">type</replaceable> [ USING <replaceable class="PARAMETER">expression</replaceable> ]
     ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> SET DEFAULT <replaceable class="PARAMETER">expression</replaceable>

doc/src/sgml/ref/create_table.sgml

@@ -22,7 +22,7 @@ PostgreSQL documentation
  <refsynopsisdiv>
 <synopsis>
 CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE [ IF NOT EXISTS ] <replaceable class="PARAMETER">table_name</replaceable> ( [
-  { <replaceable class="PARAMETER">column_name</replaceable> <replaceable class="PARAMETER">data_type</replaceable> [ DEFAULT <replaceable>default_expr</replaceable> ] [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
+  { <replaceable class="PARAMETER">column_name</replaceable> <replaceable class="PARAMETER">data_type</replaceable> [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
     | <replaceable>table_constraint</replaceable>
     | LIKE <replaceable>parent_table</replaceable> [ <replaceable>like_option</replaceable> ... ] }
     [, ... ]
@@ -34,7 +34,7 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE [ IF NOT EXISTS ] <repl
 
 CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE [ IF NOT EXISTS ] <replaceable class="PARAMETER">table_name</replaceable>
     OF <replaceable class="PARAMETER">type_name</replaceable> [ (
-  { <replaceable class="PARAMETER">column_name</replaceable> WITH OPTIONS [ DEFAULT <replaceable>default_expr</replaceable> ] [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
+  { <replaceable class="PARAMETER">column_name</replaceable> WITH OPTIONS [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
     | <replaceable>table_constraint</replaceable> }
     [, ... ]
 ) ]
@@ -48,6 +48,7 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE [ IF NOT EXISTS ] <repl
 { NOT NULL |
   NULL |
   CHECK ( <replaceable class="PARAMETER">expression</replaceable> ) |
+  DEFAULT <replaceable>default_expr</replaceable> |
   UNIQUE <replaceable class="PARAMETER">index_parameters</replaceable> |
   PRIMARY KEY <replaceable class="PARAMETER">index_parameters</replaceable> |
   REFERENCES <replaceable class="PARAMETER">reftable</replaceable> [ ( <replaceable class="PARAMETER">refcolumn</replaceable> ) ] [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ]
@@ -226,27 +227,6 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE [ IF NOT EXISTS ] <repl
     </listitem>
    </varlistentry>
 
-   <varlistentry>
-    <term><literal>DEFAULT
-    <replaceable>default_expr</replaceable></literal></term>
-    <listitem>
-     <para>
-      The <literal>DEFAULT</> clause assigns a default data value for
-      the column whose column definition it appears within.  The value
-      is any variable-free expression (subqueries and cross-references
-      to other columns in the current table are not allowed).  The
-      data type of the default expression must match the data type of the
-      column.
-     </para>
-
-     <para>
-      The default expression will be used in any insert operation that
-      does not specify a value for the column.  If there is no default
-      for a column, then the default is null.
-     </para>
-    </listitem>
-   </varlistentry>
-
    <varlistentry>
     <term><literal>INHERITS ( <replaceable>parent_table</replaceable> [, ... ] )</literal></term>
     <listitem>
@@ -421,6 +401,27 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE [ IF NOT EXISTS ] <repl
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>DEFAULT
+    <replaceable>default_expr</replaceable></literal></term>
+    <listitem>
+     <para>
+      The <literal>DEFAULT</> clause assigns a default data value for
+      the column whose column definition it appears within.  The value
+      is any variable-free expression (subqueries and cross-references
+      to other columns in the current table are not allowed).  The
+      data type of the default expression must match the data type of the
+      column.
+     </para>
+
+     <para>
+      The default expression will be used in any insert operation that
+      does not specify a value for the column.  If there is no default
+      for a column, then the default is null.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><literal>UNIQUE</> (column constraint)</term>
     <term><literal>UNIQUE ( <replaceable class="PARAMETER">column_name</replaceable> [, ... ] )</> (table constraint)</term>