Add note pointing out that read-only commands no longer consume

command IDs.

diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 8ed0e48dfd3218626094756432527f310f95e9b2..00aac8d3c98f3049edf1461ced800ec1e28b8200 100644 (file)
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -1034,12 +1034,14 @@ CREATE TABLE order_items (
    </para>
 
    <para>
-    Command
-    identifiers are also 32-bit quantities.  This creates a hard limit
+    Command identifiers are also 32-bit quantities.  This creates a hard limit
     of 2<superscript>32</> (4 billion) <acronym>SQL</acronym> commands
     within a single transaction.  In practice this limit is not a
     problem &mdash; note that the limit is on number of
     <acronym>SQL</acronym> commands, not number of rows processed.
+    Also, as of <productname>PostgreSQL</productname> 8.3, only commands
+    that actually modify the database contents will consume a command
+    identifier.
    </para>
  </sect1>