The index was not used if there were multiple IN(..) conditions.

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

@@ -6,6 +6,7 @@
  */
 package org.h2.index;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.HashSet;
@@ -206,10 +207,10 @@ public class IndexCondition {
     /**
      * Get the comparison bit mask.
      *
-     * @param conditionCount the number of index conditions
+     * @param indexConditions all index conditions
      * @return the mask
      */
-    public int getMask(int conditionCount) {
+    public int getMask(ArrayList<IndexCondition> indexConditions) {
         switch (compareType) {
         case Comparison.FALSE:
             return ALWAYS_FALSE;
@@ -217,11 +218,30 @@ public class IndexCondition {
             return EQUALITY;
         case Comparison.IN_LIST:
         case Comparison.IN_QUERY:
-            if (conditionCount > 1) {
-                // if there are more conditions, don't use the index on IN(..)
-                // IN(..) can not be combined with other conditions,
-                // otherwise the query returns the wrong result
-                return 0;
+            if (indexConditions.size() > 1) {
+                // IN(..) can not be combined with other conditions.
+                // If there are other conditions (except for other
+                // IN_ conditions), don't use the index on IN(..)
+                // otherwise the query returns the wrong result.
+                boolean beforeThis = true;
+                for (IndexCondition c : indexConditions) {
+                    if (c == this) {
+                        beforeThis = false;
+                        continue;
+                    }
+                    if (c.isEvaluatable()) {
+                        if (beforeThis) {
+                            // If there are only multiple IN_ conditions,
+                            // only the first one can be used
+                            return 0;
+                        }
+                        if (!c.isIn()) {
+                            // If there are other (non-IN_) conditions,
+                            // this one can't be used
+                            return 0;
+                        }
+                    }
+                }
             }
             return EQUALITY;
         case Comparison.BIGGER_EQUAL:
@@ -244,6 +264,16 @@ public class IndexCondition {
         return compareType == Comparison.FALSE;
     }
 
+    private boolean isIn() {
+        switch (compareType) {
+        case Comparison.IN_LIST:
+        case Comparison.IN_QUERY:
+            return true;
+        default:
+            return false;
+        }
+    }
+
     /**
      * Check if this index condition is of the type column larger or equal to
      * value.

h2/src/test/org/h2/samples/optimizations.sql

@@ -22,7 +22,7 @@ SELECT COUNT(*) FROM TEST;
 -- Display the query plan - 'direct lookup' means the index is used
 EXPLAIN SELECT COUNT(*) FROM TEST;
 --> SELECT COUNT(*)
--->    FROM PUBLIC.TEST /* PUBLIC.TEST_DATA */
+-->    FROM PUBLIC.TEST /* PUBLIC.TEST.tableScan */
 -->    /* direct lookup */
 ;
 
@@ -90,7 +90,7 @@ SELECT MIN(VALUE), MAX(VALUE) FROM TEST;
 -- Display the query plan - 'direct lookup' means it's optimized
 EXPLAIN SELECT MIN(VALUE), MAX(VALUE) FROM TEST;
 --> SELECT MIN(VALUE), MAX(VALUE)
--->    FROM PUBLIC.TEST /* PUBLIC.TEST_DATA */
+-->    FROM PUBLIC.TEST /* PUBLIC.TEST.tableScan */
 -->    /* direct lookup */
 ;
 
@@ -223,3 +223,22 @@ EXPLAIN SELECT * FROM TEST WHERE ID IN(1, 1000);
 
 DROP TABLE TEST;
 
+-------------------------------------------------------------------------------
+-- Optimize Multiple IN(..)
+-------------------------------------------------------------------------------
+-- This code snippet shows how multiple IN(...) conditions use an index.
+
+-- Initialize the data
+CREATE TABLE TEST(ID INT PRIMARY KEY, DATA INT);
+CREATE INDEX TEST_DATA ON TEST(DATA);
+
+INSERT INTO TEST SELECT X, MOD(X, 10) FROM SYSTEM_RANGE(1, 1000);
+
+-- Display the query plan
+EXPLAIN SELECT * FROM TEST WHERE ID IN (10, 20) AND DATA IN (1, 2);
+--> SELECT TEST.ID, TEST.DATA
+-->    FROM PUBLIC.TEST /* PUBLIC.PRIMARY_KEY_2: ID IN(10, 20) */
+-->    WHERE (ID IN(10, 20)) AND (DATA IN(1, 2))
+;
+
+DROP TABLE TEST;