From 43ea23a346cd32d5ae2ca1d465db6f3beb65bf13 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Mon, 13 Jun 2011 08:28:41 -0400
Subject: [PATCH] More foreign table documentation improvements.
Shigeru Hanada, with some additional wordsmithing by me
---
doc/src/sgml/ddl.sgml | 9 +++++----
doc/src/sgml/fdwhandler.sgml | 11 +++++++++++
2 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 9709dd613ff..09d7a24a25c 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -3021,10 +3021,11 @@ ANALYZE measurement;
<firstterm>foreign data wrapper</firstterm>. A foreign data wrapper is a
library that can communicate with an external data source, hiding the
details of connecting to the data source and fetching data from it. There
- are several foreign data wrappers available, which can for example read
- plain data files residing on the server, or connect to another PostgreSQL
- instance. If none of the existing foreign data wrappers suit your needs,
- you can write your own; see <xref linkend="fdwhandler">.
+ is a foreign data wrapper available as a <file>contrib</file> module,
+ which can read plain data files residing on the server. Other kind of
+ foreign data wrappers might be found as third party products. If none of
+ the existing foreign data wrappers suit your needs, you can write your
+ own; see <xref linkend="fdwhandler">.
</para>
<para>
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index fc07f129b79..c8ae861852a 100644
--- a/doc/src/sgml/fdwhandler.sgml
+++ b/doc/src/sgml/fdwhandler.sgml
@@ -179,6 +179,17 @@ IterateForeignScan (ForeignScanState *node);
are not needed, you should insert nulls in those column positions.
</para>
+ <para>
+ Note that <productname>PostgreSQL</productname>'s executor doesn't care
+ whether the rows returned violate the <literal>NOT NULL</literal>
+ constraints which were defined on the foreign table columns - but the
+ planner does care, and may optimize queries incorrectly if
+ <literal>NULL</> values are present in a column declared not to contain
+ them. If a <literal>NULL</> value is encountered when the user has
+ declared that none should be present, it may be appropriate to raise an
+ error (just as you would need to do in the case of a data type mismatch).
+ </para>
+
<para>
<programlisting>
void
--
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