The index condition columnName IS NULL was not efficient when using a clustered index.

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

@@ -74,7 +74,7 @@ class PageDataCursor implements Cursor {
     private boolean checkMax() {
         if (row != null) {
             if (maxKey != Long.MAX_VALUE) {
-                long x = current.index.getKey(row, Long.MAX_VALUE);
+                long x = current.index.getKey(row, Long.MAX_VALUE, Long.MAX_VALUE);
                 if (x > maxKey) {
                     row = null;
                     return false;

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

@@ -245,15 +245,18 @@ public class PageDataIndex extends PageIndex {
      *
      * @param row the row
      * @param ifEmpty the value to use if the row is empty
+     * @param ifNull the value to use if the column is NULL
      * @return the key
      */
-    long getKey(SearchRow row, long ifEmpty) {
+    long getKey(SearchRow row, long ifEmpty, long ifNull) {
         if (row == null) {
             return ifEmpty;
         }
         Value v = row.getValue(mainIndexColumn);
-        if (v == null || v == ValueNull.INSTANCE) {
-            return ifEmpty;
+        if (v == null) {
+            throw DbException.throwInternalError(row.toString());
+        } else if (v == ValueNull.INSTANCE) {
+            return ifNull;
         }
         return v.getLong();
     }

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

@@ -53,8 +53,10 @@ public class PageDelegateIndex extends PageIndex {
     }
 
     public Cursor find(Session session, SearchRow first, SearchRow last) {
-        long min = mainIndex.getKey(first, Long.MIN_VALUE);
-        long max = mainIndex.getKey(last, Long.MAX_VALUE);
+        long min = mainIndex.getKey(first, Long.MIN_VALUE, Long.MIN_VALUE);
+        // ifNull is MIN_VALUE as well, because the column is never NULL
+        // so avoid returning all rows (returning one row is OK)
+        long max = mainIndex.getKey(last, Long.MAX_VALUE, Long.MIN_VALUE);
         return mainIndex.find(session, min, max, false);
     }
 

h2/src/test/org/h2/test/test-1.2.txt

 --- special grammar and test cases ---------------------------------------------------------------------------------------------
+create table test(id int primary key);
+> ok
+
+insert into test values(1), (2), (3), (4);
+> update count: 4
+
+explain analyze select * from test where id is null;
+> PLAN
+> ----------------------------------------------------------------------------------------------------------
+> SELECT TEST.ID FROM PUBLIC.TEST /* PUBLIC.PRIMARY_KEY_2: ID IS NULL */ /* scanCount: 1 */ WHERE ID IS NULL
+> rows: 1
+
+drop table test;
+> ok
+
 explain analyze select 1;
 > PLAN
 > ----------------------------------------------------------------------------
@@ -3121,8 +3136,8 @@ inner join test2 on test1.id=test2.id left
 outer join test3 on test2.id=test3.id
 where test3.id is null;
 > PLAN
-> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-> SELECT TEST1.ID, TEST2.ID, TEST3.ID FROM PUBLIC.TEST1 /* PUBLIC.TEST1.tableScan */ INNER JOIN PUBLIC.TEST2 /* PUBLIC.PRIMARY_KEY_4C: ID = TEST1.ID AND ID = TEST1.ID */ ON 1=1 /* WHERE TEST1.ID = TEST2.ID */ LEFT OUTER JOIN PUBLIC.TEST3 /* PUBLIC.PRIMARY_KEY_4C0: ID = TEST2.ID AND ID IS NULL */ ON TEST2.ID = TEST3.ID WHERE (TEST3.ID IS NULL) AND (TEST1.ID = TEST2.ID)
+> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+> SELECT TEST1.ID, TEST2.ID, TEST3.ID FROM PUBLIC.TEST1 /* PUBLIC.TEST1.tableScan */ INNER JOIN PUBLIC.TEST2 /* PUBLIC.PRIMARY_KEY_4C: ID = TEST1.ID AND ID = TEST1.ID */ ON 1=1 /* WHERE TEST1.ID = TEST2.ID */ LEFT OUTER JOIN PUBLIC.TEST3 /* PUBLIC.PRIMARY_KEY_4C0: ID = TEST2.ID */ ON TEST2.ID = TEST3.ID WHERE (TEST3.ID IS NULL) AND (TEST1.ID = TEST2.ID)
 > rows: 1
 
 insert into test1 select x from system_range(2, 1000);
@@ -3141,8 +3156,8 @@ inner join test2 on test1.id=test2.id
 left outer join test3 on test2.id=test3.id
 where test3.id is null;
 > PLAN
-> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-> SELECT TEST1.ID, TEST2.ID, TEST3.ID FROM PUBLIC.TEST2 /* PUBLIC.TEST2.tableScan */ LEFT OUTER JOIN PUBLIC.TEST3 /* PUBLIC.PRIMARY_KEY_4C0: ID = TEST2.ID AND ID IS NULL */ ON TEST2.ID = TEST3.ID INNER JOIN PUBLIC.TEST1 /* PUBLIC.PRIMARY_KEY_4: ID = TEST2.ID */ ON 1=1 WHERE (TEST3.ID IS NULL) AND (TEST1.ID = TEST2.ID)
+> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+> SELECT TEST1.ID, TEST2.ID, TEST3.ID FROM PUBLIC.TEST2 /* PUBLIC.TEST2.tableScan */ LEFT OUTER JOIN PUBLIC.TEST3 /* PUBLIC.PRIMARY_KEY_4C0: ID = TEST2.ID */ ON TEST2.ID = TEST3.ID INNER JOIN PUBLIC.TEST1 /* PUBLIC.PRIMARY_KEY_4: ID = TEST2.ID */ ON 1=1 WHERE (TEST3.ID IS NULL) AND (TEST1.ID = TEST2.ID)
 > rows: 1
 
 SELECT TEST1.ID, TEST2.ID, TEST3.ID