1 files changed, 17 insertions, 17 deletions
diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index afe213910c7..69f3355eded 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -1184,26 +1184,26 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
    </para>
 
    <para>
-    When a column is added with <literal>ADD COLUMN</literal>, all existing
-    rows in the table are initialized with the column's default value
-    (NULL if no <literal>DEFAULT</literal> clause is specified).
-    If there is no <literal>DEFAULT</literal> clause, this is merely a metadata
-    change and does not require any immediate update of the table's data;
-    the added NULL values are supplied on readout, instead.
+    When a column is added with <literal>ADD COLUMN</literal> and a
+    non-volatile <literal>DEFAULT</literal> is specified, the default is
+    evaluated at the time of the statement and the result stored in the
+    table's metadata.  That value will be used for the column for all existing
+    rows.  If no <literal>DEFAULT</literal> is specified, NULL is used.  In
+    neither case is a rewrite of the table required.
    </para>
 
    <para>
-    Adding a column with a <literal>DEFAULT</literal> clause or changing the type of
-    an existing column will require the entire table and its indexes to be
-    rewritten.  As an exception when changing the type of an existing column,
-    if the <literal>USING</literal> clause does not change the column
-    contents and the old type is either binary coercible to the new type or
-    an unconstrained domain over the new type, a table rewrite is not needed;
-    but any indexes on the affected columns must still be rebuilt.  Adding or
-    removing a system <literal>oid</literal> column also requires rewriting the entire
-    table.  Table and/or index rebuilds may take a significant amount of time
-    for a large table; and will temporarily require as much as double the disk
-    space.
+    Adding a column with a volatile <literal>DEFAULT</literal> or
+    changing the type of an existing column will require the entire table and
+    its indexes to be rewritten. As an exception, when changing the type of an
+    existing column, if the <literal>USING</literal> clause does not change
+    the column contents and the old type is either binary coercible to the new
+    type or an unconstrained domain over the new type, a table rewrite is not
+    needed; but any indexes on the affected columns must still be rebuilt.
+    Adding or removing a system <literal>oid</literal> column also requires
+    rewriting the entire table.  Table and/or index rebuilds may take a
+    significant amount of time for a large table; and will temporarily require
+    as much as double the disk space.
    </para>
 
    <para>