Support "x IS NOT NULL" clauses as indexscan conditions. This turns out

to be just a minor extension of the previous patch that made "x IS NULL"
indexable, because we can treat the IS NOT NULL condition as if it were
"x < NULL" or "x > NULL" (depending on the index's NULLS FIRST/LAST option),
just like IS NULL is treated like "x = NULL".  Aside from any possible
usefulness in its own right, this is an important improvement for
index-optimized MAX/MIN aggregates: it is now reliably possible to get
a column's min or max value cheaply, even when there are a lot of nulls
cluttering the interesting end of the index.

3 files changed, 10 insertions, 10 deletions

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 0acd79361bd..9f81dc209ff 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.215 2009/12/29 20:11:42 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.216 2010/01/01 21:53:48 tgl Exp $ -->
 <!--
  Documentation of the system catalogs, directed toward PostgreSQL developers
  -->
@@ -466,7 +466,7 @@
       <entry><structfield>amsearchnulls</structfield></entry>
       <entry><type>bool</type></entry>
       <entry></entry>
-      <entry>Does the access method support IS NULL searches?</entry>
+      <entry>Does the access method support IS NULL/NOT NULL searches?</entry>
      </row>
 
      <row>
diff --git a/doc/src/sgml/indexam.sgml b/doc/src/sgml/indexam.sgml
index b81cd27d313..97af5464456 100644
--- a/doc/src/sgml/indexam.sgml
+++ b/doc/src/sgml/indexam.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/indexam.sgml,v 2.31 2009/07/29 20:56:17 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/indexam.sgml,v 2.32 2010/01/01 21:53:49 tgl Exp $ -->
 
 <chapter id="indexam">
  <title>Index Access Method Interface Definition</title>
@@ -134,7 +134,8 @@
    null values.  An index access method that sets
    <structfield>amindexnulls</structfield> may also set
    <structfield>amsearchnulls</structfield>, indicating that it supports
-   <literal>IS NULL</> clauses as search conditions.
+   <literal>IS NULL</> and <literal>IS NOT NULL</> clauses as search
+   conditions.
   </para>
 
  </sect1>
diff --git a/doc/src/sgml/indices.sgml b/doc/src/sgml/indices.sgml
index 7801b099f22..0ab3e25e80b 100644
--- a/doc/src/sgml/indices.sgml
+++ b/doc/src/sgml/indices.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/indices.sgml,v 1.79 2009/08/07 20:54:31 alvherre Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/indices.sgml,v 1.80 2010/01/01 21:53:49 tgl Exp $ -->
 
 <chapter id="indexes">
  <title id="indexes-title">Indexes</title>
@@ -147,8 +147,8 @@ CREATE INDEX test1_id_index ON test1 (id);
 
    Constructs equivalent to combinations of these operators, such as
    <literal>BETWEEN</> and <literal>IN</>, can also be implemented with
-   a B-tree index search.  Also, an <literal>IS NULL</> condition on
-   an index column can be used with a B-tree index.
+   a B-tree index search.  Also, an <literal>IS NULL</> or <literal>IS NOT
+   NULL</> condition on an index column can be used with a B-tree index.
   </para>
 
   <para>
@@ -180,8 +180,7 @@ CREATE INDEX test1_id_index ON test1 (id);
    Hash indexes can only handle simple equality comparisons.
    The query planner will consider using a hash index whenever an
    indexed column is involved in a comparison using the
-   <literal>=</literal> operator.  (Hash indexes do not support
-   <literal>IS NULL</> searches.)
+   <literal>=</literal> operator.
    The following command is used to create a hash index:
 <synopsis>
 CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable> USING hash (<replaceable>column</replaceable>);
@@ -1025,7 +1024,7 @@ SELECT am.amname AS index_method,
      real statistics, some default values are assumed, which are
      almost certain to be inaccurate.  Examining an application's
      index usage without having run <command>ANALYZE</command> is
-     therefore a lost cause. 
+     therefore a lost cause.
      See <xref linkend="vacuum-for-statistics" endterm="vacuum-for-statistics-title">
      and <xref linkend="autovacuum" endterm="autovacuum-title"> for more information.
     </para>