Trying to alter a temporary table threw a strange exception.

h2/src/main/org/h2/command/ddl/AlterTableAlterColumn.java

@@ -213,6 +213,9 @@ public class AlterTableAlterColumn extends SchemaCommand {
     }
 
     private void copyData() throws SQLException {
+        if (table.isTemporary()) {
+            throw Message.getUnsupportedException("TEMP TABLE");
+        }
         Database db = session.getDatabase();
         String tempName = db.getTempTableName(session.getId());
         Column[] columns = table.getColumns();

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

@@ -10,7 +10,6 @@ import java.sql.Connection;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
-
 import org.h2.test.TestBase;
 
 /**
@@ -30,6 +29,7 @@ public class TestTempTables extends TestBase {
     public void test() throws SQLException {
         deleteDb("tempTables");
         Connection c1 = getConnection("tempTables");
+        testAlter(c1);
         Connection c2 = getConnection("tempTables");
         testConstraints(c1, c2);
         testTables(c1, c2);
@@ -39,6 +39,23 @@ public class TestTempTables extends TestBase {
         deleteDb("tempTables");
     }
 
+    private void testAlter(Connection conn) throws SQLException {
+        Statement stat;
+        stat = conn.createStatement();
+        stat.execute("create temporary table test(id varchar)");
+        stat.execute("create index idx1 on test(id)");
+        stat.execute("drop index idx1");
+        stat.execute("create index idx1 on test(id)");
+        stat.execute("insert into test select x from system_range(1, 10)");
+        try {
+            stat.execute("alter table test add column x int");
+            fail();
+        } catch (SQLException e) {
+            assertKnownException(e);
+        }
+        stat.execute("drop table test");
+    }
+
     private void testConstraints(Connection conn1, Connection conn2) throws SQLException {
         Statement s1 = conn1.createStatement(), s2 = conn2.createStatement();
         s1.execute("create local temporary table test(id int unique)");