New system function TRANSACTION_ID().

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

@@ -100,7 +100,7 @@ public class Function extends Expression implements FunctionCall {
             CASE = 206, NEXTVAL = 207, CURRVAL = 208, ARRAY_GET = 209, CSVREAD = 210, CSVWRITE = 211,
             MEMORY_FREE = 212, MEMORY_USED = 213, LOCK_MODE = 214, SCHEMA = 215, SESSION_ID = 216, ARRAY_LENGTH = 217,
             LINK_SCHEMA = 218, GREATEST = 219, LEAST = 220, CANCEL_SESSION = 221, SET = 222, TABLE = 223, TABLE_DISTINCT = 224,
-            FILE_READ = 225;
+            FILE_READ = 225, TRANSACTION_ID = 226;
 
     private static final int VAR_ARGS = -1;
 
@@ -318,6 +318,7 @@ public class Function extends Expression implements FunctionCall {
         addFunction("CANCEL_SESSION", CANCEL_SESSION, 1, Value.BOOLEAN);
         addFunction("SET", SET, 2, Value.NULL, false, false);
         addFunction("FILE_READ", FILE_READ, VAR_ARGS, Value.NULL, false, true);
+        addFunctionNotConst("TRANSACTION_ID", TRANSACTION_ID, 0, Value.STRING);
 
         // TableFunction
         addFunctionWithNull("TABLE", TABLE, VAR_ARGS, Value.RESULT_SET);
@@ -817,6 +818,10 @@ public class Function extends Expression implements FunctionCall {
             result = ValueBoolean.get(cancelStatement(session, v0.getInt()));
             break;
         }
+        case TRANSACTION_ID: {
+            result = session.getTransactionId();
+            break;
+        }
         default:
             result = null;
         }

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

@@ -44,6 +44,7 @@ public class TestFunctions extends TestBase implements AggregateFunction {
 
     public void test() throws Exception {
         deleteDb("functions");
+        testTransactionId();
         testPrecision();
         testVarArgs();
         testAggregate();
@@ -52,6 +53,30 @@ public class TestFunctions extends TestBase implements AggregateFunction {
         deleteDb("functions");
     }
 
+    private void testTransactionId() throws SQLException {
+        if (config.memory) {
+            return;
+        }
+        Connection conn = getConnection("functions");
+        Statement stat = conn.createStatement();
+        stat.execute("create table test(id int)");
+        ResultSet rs;
+        rs = stat.executeQuery("call transaction_id()");
+        rs.next();
+        assertTrue(rs.getString(1) == null && rs.wasNull());
+        stat.execute("insert into test values(1)");
+        rs = stat.executeQuery("call transaction_id()");
+        rs.next();
+        assertTrue(rs.getString(1) == null && rs.wasNull());
+        conn.setAutoCommit(false);
+        stat.execute("delete from test");
+        rs = stat.executeQuery("call transaction_id()");
+        rs.next();
+        assertTrue(rs.getString(1) != null);
+        stat.execute("drop table test");
+        conn.close();
+    }
+
     private void testPrecision() throws SQLException {
         Connection conn = getConnection("functions");
         Statement stat = conn.createStatement();