Conditions of the form columnName IS NULL now use an index.

h2/src/docsrc/html/changelog.html

@@ -18,14 +18,16 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>H2 Console: when the settings were not stored yet (for example when running for the first time),
-	the last recently used settings were not stored. A workaround was to create the file 
-	".h2.server.properties" manually in the current user home directory, with the contents:
-	webAllowOthers=false, webPort=8082, webSSL=false,
-	0=Generic H2 (Embedded)|org.h2.Driver|jdbc\:h2\:~/test|sa
-	(where a comma is a newline).
+<ul><li>Conditions of the form columnName IS NULL now use an index. To disable this feature,
+    set the system property h2.optimizeIsNull to false.
+</li><li>H2 Console: when the settings were not stored yet (for example when running for the first time),
+    the last recently used settings were not stored. A workaround was to create the file
+    ".h2.server.properties" manually in the current user home directory, with the contents:
+    webAllowOthers=false, webPort=8082, webSSL=false,
+    0=Generic H2 (Embedded)|org.h2.Driver|jdbc\:h2\:~/test|sa
+    (where a comma is a newline).
 </li><li>The source code is now switched to Java 6 (JDK 1.6) by default.
-	Java 5 (JDK 1.5) is still supported, and the jar file is still compiled for Java 5.
+    Java 5 (JDK 1.5) is still supported, and the jar file is still compiled for Java 5.
 </li><li>The BOM (the byte-order-mark) character 0xfeff at the beginning of the file is ignored.
     This is for compatibility with Microsoft Excel.
 </li><li>When opening an existing database, the cache size is set to at most

h2/src/main/org/h2/constant/SysProperties.java

@@ -433,6 +433,12 @@ public class SysProperties {
      */
     public static final boolean OPTIMIZE_IN_LIST = getBooleanSetting("h2.optimizeInList", true);
 
+    /**
+     * System property <code>h2.optimizeIsNull</code> (default: false).<br />
+     * Use an index for condition of the form columnName IS NULL.
+     */
+    public static final boolean OPTIMIZE_IS_NULL = getBooleanSetting("h2.optimizeIsNull", true);
+
     /**
      * System property <code>h2.optimizeOr</code> (default: false).<br />
      * Convert (C=? OR C=?) to (C IN(?, ?)).

h2/src/main/org/h2/expression/Comparison.java

@@ -283,9 +283,6 @@ public class Comparison extends Condition {
     }
 
     public void createIndexConditions(Session session, TableFilter filter) {
-        if (right == null) {
-            return;
-        }
         ExpressionColumn l = null;
         if (left instanceof ExpressionColumn) {
             l = (ExpressionColumn) left;
@@ -293,6 +290,17 @@ public class Comparison extends Condition {
                 l = null;
             }
         }
+        if (right == null) {
+            if (l != null) {
+                switch (compareType) {
+                case IS_NULL:
+                    if (SysProperties.OPTIMIZE_IS_NULL) {
+                        filter.addIndexCondition(IndexCondition.get(Comparison.EQUAL, l, ValueExpression.getNull()));
+                    }
+                }
+            }
+            return;
+        }
         ExpressionColumn r = null;
         if (right instanceof ExpressionColumn) {
             r = (ExpressionColumn) right;

h2/src/main/org/h2/index/IndexCursor.java

@@ -8,6 +8,8 @@ package org.h2.index;
 
 import java.util.ArrayList;
 import java.util.HashSet;
+
+import org.h2.constant.SysProperties;
 import org.h2.engine.Session;
 import org.h2.expression.Comparison;
 import org.h2.message.DbException;
@@ -117,10 +119,12 @@ public class IndexCursor implements Cursor {
                     inList = null;
                     inResult = null;
                 }
-                if (isStart && isEnd) {
-                    if (v == ValueNull.INSTANCE) {
-                        // join on a column=NULL is always false
-                        alwaysFalse = true;
+                if (!SysProperties.OPTIMIZE_IS_NULL) {
+                    if (isStart && isEnd) {
+                        if (v == ValueNull.INSTANCE) {
+                            // join on a column=NULL is always false
+                            alwaysFalse = true;
+                        }
                     }
                 }
             }
@@ -166,7 +170,24 @@ public class IndexCursor implements Cursor {
         } else if (b == null) {
             return a;
         }
+        if (SysProperties.OPTIMIZE_IS_NULL) {
+            // IS NULL must be checked later
+            if (a == ValueNull.INSTANCE) {
+                return b;
+            } else if (b == ValueNull.INSTANCE) {
+                return a;
+            }
+        }
         int comp = a.compareTo(b, table.getDatabase().getCompareMode());
+        if (comp == 0) {
+            return a;
+        }
+        if (SysProperties.OPTIMIZE_IS_NULL) {
+            if (a == ValueNull.INSTANCE || b == ValueNull.INSTANCE) {
+                // column IS NULL AND column <op> <not null> is always false
+                return null;
+            }
+        }
         if (!bigger) {
             comp = -comp;
         }