Fixed the Oracle mode: Oracle allows multiple rows only where all columns of the…

Fixed the Oracle mode: Oracle allows multiple rows only where all columns of the unique index are NULL. 

h2/src/main/org/h2/engine/Mode.java

@@ -80,6 +80,13 @@ public class Mode {
      */
     public boolean uniqueIndexSingleNull;
 
+    /**
+     * When using unique indexes, multiple rows with NULL in all columns
+     * are allowed, however it is not allowed to have multiple rows with the
+     * same values otherwise. This is how Oracle works.
+     */
+    public boolean uniqueIndexSingleNullExceptAllColumnsAreNull;
+
     /**
      * If the syntax [OFFSET .. ROW] [FETCH ... ONLY] should be supported.
      * This is an alternative syntax for LIMIT .. OFFSET.
@@ -121,6 +128,10 @@ public class Mode {
         add(mode);
 
         mode = new Mode("Oracle");
+        mode.uniqueIndexSingleNullExceptAllColumnsAreNull = true;
+        add(mode);
+
+        mode = new Mode("DB2");
         add(mode);
 
     }

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

@@ -11,6 +11,7 @@ import java.sql.SQLException;
 import org.h2.constant.ErrorCode;
 import org.h2.engine.Constants;
 import org.h2.engine.DbObject;
+import org.h2.engine.Mode;
 import org.h2.engine.Session;
 import org.h2.message.Message;
 import org.h2.message.Trace;
@@ -248,8 +249,18 @@ public abstract class BaseIndex extends SchemaObjectBase implements Index {
     }
 
     public boolean containsNullAndAllowMultipleNull(Session session, Row newRow) {
-        if (session.getDatabase().getMode().uniqueIndexSingleNull) {
+        Mode mode = session.getDatabase().getMode();
+        if (mode.uniqueIndexSingleNull) {
             return false;
+        } else if (mode.uniqueIndexSingleNullExceptAllColumnsAreNull) {
+            for (int i = 0; i < columns.length; i++) {
+                int index = columnIds[i];
+                Value v = newRow.getValue(index);
+                if (v != ValueNull.INSTANCE) {
+                    return false;
+                }
+            }
+            return true;
         }
         for (int i = 0; i < columns.length; i++) {
             int index = columnIds[i];

h2/src/test/org/h2/test/db/TestCompatibility.java

@@ -25,6 +25,7 @@ public class TestCompatibility extends TestBase {
         conn = getConnection("compatibility");
 
         testUniqueIndexSingleNull();
+        testUniqueIndexOracle();
         testHsqlDb();
         testMySQL();
 
@@ -51,6 +52,30 @@ public class TestCompatibility extends TestBase {
         }
     }
 
+    private void testUniqueIndexOracle() throws Exception {
+        Statement stat = conn.createStatement();
+        stat.execute("SET MODE ORACLE");
+        stat.execute("create table t2(c1 int, c2 int)");
+        stat.execute("create unique index i2 on t2(c1, c2)");
+        stat.execute("insert into t2 values (null, 1)");
+        try {
+            stat.execute("insert into t2 values (null, 1)");
+            fail();
+        } catch (SQLException e) {
+            assertKnownException(e);
+        }
+        stat.execute("insert into t2 values (null, null)");
+        stat.execute("insert into t2 values (null, null)");
+        stat.execute("insert into t2 values (1, null)");
+        try {
+            stat.execute("insert into t2 values (1, null)");
+            fail();
+        } catch (SQLException e) {
+            assertKnownException(e);
+        }
+        stat.execute("DROP TABLE T2");
+    }
+
     private void testHsqlDb() throws Exception {
         Statement stat = conn.createStatement();
         stat.execute("DROP TABLE TEST IF EXISTS; CREATE TABLE TEST(ID INT PRIMARY KEY); ");