ZMySQLDA: support isolation level per connector.

product/ZMySQLDA/connectionAdd.dtml

@@ -56,7 +56,7 @@
     <dd>
       The connection string used for Z MySQL Database Connection is of the form:
       <br />
-      <code>[%ssl_name] [*lock] [+/-][database][@host[:port]] [user [password [unix_socket]]]</code>
+      <code>[%ssl_name] [*lock] [!isolation-level] [+/-][database][@host[:port]] [user [password [unix_socket]]]</code>
       <br />
       or typically:
       <br />
@@ -103,6 +103,12 @@
       you'll get an error in the logs, and inconsistent data. In this
       respect, it's equivalent to transactions turned off.
     </dd>
+    <dd>
+      !<em>isolation_level</em> at the begining of the connection string
+      will set the transaction isolation level in each transaction. The
+      value should be one of REPEATABLE-READ, READ-COMMITTED,
+      READ-UNCOMMITTED or SERIALIZABLE.
+    </dd>
     <dd>
       Transactions are highly recommended. Using a named lock in
       conjunctions with transactions is probably pointless.

product/ZMySQLDA/db.py

@@ -244,7 +244,7 @@ class DB(TM):
         self._use_TM = transactional or self._mysql_lock
 
     def _parse_connection_string(self):
-        self._mysql_lock = self._try_transactions = None
+        self._mysql_lock = self._try_transactions = self._isolation_level = None
         self._kw_args = kwargs = {'conv': self.conv}
         items = self._connection.split()
         if not items:
@@ -262,6 +262,8 @@ class DB(TM):
             del items[0]
         if items[0][0] == "*":
             self._mysql_lock = items.pop(0)[1:]
+        if items[0][0] == "!":
+            self._isolation_level = items.pop(0)[1:]
         db = items.pop(0)
         if '@' in db:
             db, host = db.split('@', 1)
@@ -491,6 +493,8 @@ class DB(TM):
         try:
             self._transaction_begun = True
             if self._transactions:
+                if self._isolation_level:
+                    self._query("SET TRANSACTION ISOLATION LEVEL %s" % self._isolation_level.replace('-', ' '))
                 self._query("BEGIN", allow_reconnect=True)
             if self._mysql_lock:
                 self._query("SELECT GET_LOCK('%s',0)" % self._mysql_lock, allow_reconnect=not self._transactions)