--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/nabble/model/DbUpdater.java	Thu Mar 21 19:15:52 2019 -0600
@@ -0,0 +1,108 @@
+package nabble.model;
+
+import java.sql.Connection;
+import java.sql.Statement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.Map;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import fschmidt.db.DbDatabase;
+
+
+final class DbUpdater {
+	private static final Logger logger = LoggerFactory.getLogger(DbUpdater.class);
+
+	final DbDatabase db;
+	final String schema;
+	private int dbVersion;
+	Connection con;
+	Statement stmt;
+
+	DbUpdater(DbDatabase db,String schema) {
+		this.db = db;
+		this.schema = schema;
+		dbVersion = databaseVersion();
+	}
+
+	int databaseVersion() {
+		return databaseVersion(db,schema);
+	}
+
+	static int databaseVersion(DbDatabase db,String schema) {
+		try {
+			Connection con = db.getConnection();
+			try {
+				Statement stmt = con.createStatement();
+				ResultSet rs = stmt.executeQuery(
+					"select version from "+schema+".version"
+				);
+				rs.next();
+				int dbVersion = rs.getInt("version");
+				stmt.close();
+				return dbVersion;
+			} finally {
+				con.close();
+			}
+		} catch(SQLException e) {
+			throw new RuntimeException(e);
+		}
+	}
+
+	int dbVersion() {
+		return dbVersion;
+	}
+
+	void begin()
+		throws SQLException
+	{
+		con = db.getConnection();
+		con.setAutoCommit(false);
+		stmt = con.createStatement(ResultSet.TYPE_FORWARD_ONLY,ResultSet.CONCUR_UPDATABLE);
+		logger.error(schema+" step "+dbVersion);
+	}
+
+	void commit()
+		throws SQLException
+	{
+		stmt.executeUpdate(
+			"update "+schema+".version set version=" + (++dbVersion)
+		);
+		stmt.close();
+		con.commit();
+		con.close();
+		con = null;
+	}
+
+	void exec(String sql)
+		throws SQLException
+	{
+		if( sql != null ) {
+			if( sql.trim().toLowerCase().startsWith("select ") ) {
+				stmt.executeQuery(sql);
+			} else {
+				stmt.executeUpdate(sql);
+			}
+		}
+	}
+
+	void execStep(String sql)
+		throws SQLException
+	{
+		begin();
+		exec(sql);
+		commit();
+	}
+
+	void close() {
+		if( con != null ) {
+			try {
+				con.close();
+			} catch(SQLException e) {
+				logger.error(schema,e);
+			}
+			con = null;
+		}
+	}
+
+}