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.

1 files changed, 14 insertions, 1 deletions

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>