Queries using multiple IN(..) conditions on the same table could cause repeated…

Queries using multiple IN(..) conditions on the same table could cause repeated rows in the result set.

h2/src/docsrc/html/changelog.html

@@ -18,7 +18,8 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>Translation: Lubomir Grajciar translated the H2 Console as well as all error message to Slovensky. Thanks a lot!
+<ul><li>Queries using multiple IN(..) conditions on the same table could cause repeated rows in the result set.
+</li><li>Translation: Lubomir Grajciar translated the H2 Console as well as all error message to Slovensky. Thanks a lot!
 </li><li>There was a possible Java level deadlock when opening an uninitialized database and using
     a file system that also opened a database.
 </li><li>When killing the process while the database was writing a checkpoint or while it was closing,

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

@@ -77,14 +77,18 @@ public class IndexCursor implements Cursor {
             Column column = condition.getColumn();
             if (condition.getCompareType() == Comparison.IN_LIST) {
                 if (start == null && end == null) {
-                    this.inColumn = column;
-                    inList = condition.getCurrentValueList(s);
-                    inListIndex = 0;
+                    if (canUseIndexForIn(column)) {
+                        this.inColumn = column;
+                        inList = condition.getCurrentValueList(s);
+                        inListIndex = 0;
+                    }
                 }
             } else if (condition.getCompareType() == Comparison.IN_QUERY) {
                 if (start == null && end == null) {
-                    this.inColumn = column;
-                    inResult = condition.getCurrentResult(s);
+                    if (canUseIndexForIn(column)) {
+                        this.inColumn = column;
+                        inResult = condition.getCurrentResult(s);
+                    }
                 }
             } else {
                 Value v = condition.getCurrentValue(s);
@@ -128,6 +132,19 @@ public class IndexCursor implements Cursor {
         }
     }
 
+    private boolean canUseIndexForIn(Column column) {
+        if (inColumn != null) {
+            // only one IN(..) condition can be used at the same time
+            return false;
+        }
+        // The first column of the index must match this column,
+        // or it must be a VIEW indexe (where the column is null).
+        // Multiple IN conditions with views are not supported, see
+        // IndexCondition.getMask.
+        IndexColumn idxCol = indexColumns[0];
+        return idxCol == null || idxCol.column == column;
+    }
+
     private SearchRow getSearchRow(SearchRow row, int id, Value v, boolean max) {
         if (row == null) {
             row = table.getTemplateRow();

h2/src/test/org/h2/test/testSimple.in.txt

+create table test(a int, b int, unique(a, b));
+insert into test values(1,1), (1,2);
+select count(*) from test where a in(1,2) and b in(1,2);
+> 2;
+drop table test;
 create memory temp table test(name varchar primary key);
 select index_class from information_schema.indexes where table_name = 'TEST';
 > org.h2.index.TreeIndex;