From f213131f2024bcb85aea7d2a7dfadef6a0ee1b31 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 28 Sep 2006 20:51:43 +0000
Subject: Fix IS NULL and IS NOT NULL tests on row-valued expressions to
 conform to the SQL spec, viz IS NULL is true if all the row's fields are
 null, IS NOT NULL is true if all the row's fields are not null.  The former
 coding got this right for a limited number of cases with IS NULL (ie, those
 where it could disassemble a ROW constructor at parse time), but was entirely
 wrong for IS NOT NULL.  Per report from Teodor.

I desisted from changing the behavior for arrays, since on closer inspection
it's not clear that there's any support for that in the SQL spec.  This
probably needs more consideration.
---
 doc/src/sgml/func.sgml | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

(limited to 'doc/src')

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index b3fe74fe502..978309d59ea 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.340 2006/09/22 16:20:00 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.341 2006/09/28 20:51:41 tgl Exp $ -->
 
  <chapter id="functions">
   <title>Functions and Operators</title>
@@ -338,6 +338,19 @@
    </para>
   </tip>
 
+  <note>
+   <para>
+    If the <replaceable>expression</replaceable> is row-valued, then
+    <literal>IS NULL</> is true when the row expression itself is null
+    or when all the row's fields are null, while
+    <literal>IS NOT NULL</> is true when the row expression itself is non-null
+    and all the row's fields are non-null.
+    This definition conforms to the SQL standard, and is a change from the
+    inconsistent behavior exhibited by <productname>PostgreSQL</productname>
+    versions prior to 8.2.
+   </para>
+  </note>
+
    <para>
     <indexterm>
      <primary>IS DISTINCT FROM</primary>
-- 
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