The 7.5 backend allows isolation levels that aren't natively supported

by "rounding up" to the next stronger supported isolation level.  This
adds support for these levels to the JDBC driver.

Also fix a bug where setting an isolation level would set a class
member variable regardless of wether the call to the backend succeeded
or not.  I believe this only affects pre 7.1 servers, but correct is
correct.

org/postgresql/jdbc1/AbstractJdbc1Connection.java

@@ -1255,12 +1255,12 @@ public void setAutoCommit(boolean autoCommit) throws SQLException
 		{
 			if (haveMinimumServerVersion("7.1"))
 			{
-				execSQL("begin;" + getIsolationLevelSQL());
+				execSQL("begin;");
 			}
 			else
 			{
 				execSQL("begin");
-				execSQL(getIsolationLevelSQL());
+				execSQL(getPre71IsolationLevelSQL(isolationLevel));
 			}
 		}
 		this.autoCommit = autoCommit;
@@ -1294,13 +1294,13 @@ public void commit() throws SQLException
 		//TODO: delay starting new transaction until first command
 		if (haveMinimumServerVersion("7.1"))
 		{
-			execSQL("commit;begin;" + getIsolationLevelSQL());
+			execSQL("commit;begin;");
 		}
 		else
 		{
 			execSQL("commit");
 			execSQL("begin");
-			execSQL(getIsolationLevelSQL());
+			execSQL(getPre71IsolationLevelSQL(isolationLevel));
 		}
 	}
 
@@ -1319,13 +1319,13 @@ public void rollback() throws SQLException
 		//TODO: delay starting transaction until first command
 		if (haveMinimumServerVersion("7.1"))
 		{
-			execSQL("rollback; begin;" + getIsolationLevelSQL());
+			execSQL("rollback; begin;");
 		}
 		else
 		{
 			execSQL("rollback");
 			execSQL("begin");
-			execSQL(getIsolationLevelSQL());
+			execSQL(getPre71IsolationLevelSQL(isolationLevel));
 		}
 	}
 
@@ -1391,30 +1391,34 @@ public void setTransactionIsolation(int level) throws SQLException
 		//each transaction, thus adding complexity below.
 		//When we decide to drop support for servers older than 7.1
 		//this can be simplified
-		isolationLevel = level;
 		String isolationLevelSQL;
 
 		if (!haveMinimumServerVersion("7.1"))
 		{
-			isolationLevelSQL = getIsolationLevelSQL();
+			isolationLevelSQL = getPre71IsolationLevelSQL(level);
 		}
 		else
 		{
-			isolationLevelSQL = "SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL ";
-			switch (isolationLevel)
-			{
-				case Connection.TRANSACTION_READ_COMMITTED:
-					isolationLevelSQL += "READ COMMITTED";
-					break;
-				case Connection.TRANSACTION_SERIALIZABLE:
-					isolationLevelSQL += "SERIALIZABLE";
-					break;
-				default:
-					throw new PSQLException("postgresql.con.isolevel", PSQLState.TRANSACTION_STATE_INVALID,
-											new Integer(isolationLevel));
-			}
+			isolationLevelSQL = "SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL " + getIsolationLevelName(level);
 		}
 		execSQL(isolationLevelSQL);
+		isolationLevel = level;
+	}
+
+	protected String getIsolationLevelName(int level) throws SQLException
+	{
+		boolean pg75 = haveMinimumServerVersion("7.5");
+
+		if (level == Connection.TRANSACTION_READ_COMMITTED) {
+			return " READ COMMITTED";
+		} else if (level == Connection.TRANSACTION_SERIALIZABLE) {
+			return " SERIALIZABLE";
+		} else if (pg75 && level == Connection.TRANSACTION_READ_UNCOMMITTED) {
+			return " READ UNCOMMITTED";
+		} else if (pg75 && level == Connection.TRANSACTION_REPEATABLE_READ) {
+			return " REPEATABLE READ";
+		}
+		throw new PSQLException("postgresql.con.isolevel", PSQLState.TRANSACTION_STATE_INVALID, new Integer(level));
 	}
 
 	/*
@@ -1426,30 +1430,9 @@ public void setTransactionIsolation(int level) throws SQLException
 	 * servers, and should be removed when support for these older
 	 * servers are dropped
 	 */
-	protected String getIsolationLevelSQL() throws SQLException
+	protected String getPre71IsolationLevelSQL(int level) throws SQLException
 	{
-		//7.1 and higher servers have a default specified so
-		//no additional SQL is required to set the isolation level
-		if (haveMinimumServerVersion("7.1"))
-		{
-			return "";
-		}
-		StringBuffer sb = new StringBuffer("SET TRANSACTION ISOLATION LEVEL");
-
-		switch (isolationLevel)
-		{
-			case Connection.TRANSACTION_READ_COMMITTED:
-				sb.append(" READ COMMITTED");
-				break;
-
-			case Connection.TRANSACTION_SERIALIZABLE:
-				sb.append(" SERIALIZABLE");
-				break;
-
-			default:
-				throw new PSQLException("postgresql.con.isolevel", PSQLState.TRANSACTION_STATE_INVALID, new Integer(isolationLevel));
-		}
-		return sb.toString();
+		return "SET TRANSACTION ISOLATION LEVEL " + getIsolationLevelName(level);
 	}
 
 	/*

org/postgresql/jdbc1/AbstractJdbc1DatabaseMetaData.java

@@ -1606,6 +1606,8 @@ public boolean supportsTransactionIsolationLevel(int level) throws SQLException
 		if (level == Connection.TRANSACTION_SERIALIZABLE ||
 				level == Connection.TRANSACTION_READ_COMMITTED)
 			return true;
+		else if (connection.haveMinimumServerVersion("7.5") && (level == Connection.TRANSACTION_READ_UNCOMMITTED || level == Connection.TRANSACTION_REPEATABLE_READ))
+			return true;
 		else
 			return false;
 	}