Commit 220993bc authored by Malcolm Tredinnick's avatar Malcolm Tredinnick
Browse files

Added savepoint support to the transaction code. 

This is a no-op for most databases. Only necessary on PostgreSQL so that we can
do things which will possibly intentionally raise an IntegrityError and not
have to rollback the entire transaction. Not supported for PostgreSQL versions
prior to 8.0, so should be used sparingly in internal Django code.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8314 bcc190cf-cafb-0310-a4f2-bffc1f526a37
parent e73bf2bd

django/db/backends/__init__.py

+43 −8
Original line number Diff line number Diff line
@@ -31,6 +31,21 @@ class BaseDatabaseWrapper(local): 
        if self.connection is not None:

            return self.connection.rollback()



    def _savepoint(self, sid):

        if not self.features.uses_savepoints:

            return

        self.connection.cursor().execute(self.ops.savepoint_create_sql(sid))



    def _savepoint_rollback(self, sid):

        if not self.features.uses_savepoints:

            return

        self.connection.cursor().execute(self.ops.savepoint_rollback_sql(sid))



    def _savepoint_commit(self, sid):

        if not self.features.uses_savepoints:

            return

        self.connection.cursor().execute(self.ops.savepoint_commit_sql(sid))



    def close(self):

        if self.connection is not None:

            self.connection.close()
@@ -55,6 +70,7 @@ class BaseDatabaseFeatures(object): 
    update_can_self_select = True

    interprets_empty_strings_as_nulls = False

    can_use_chunked_reads = True

    uses_savepoints = False



class BaseDatabaseOperations(object):

    """
@@ -226,6 +242,26 @@ class BaseDatabaseOperations(object): 
        """

        raise NotImplementedError



    def savepoint_create_sql(self, sid):

        """

        Returns the SQL for starting a new savepoint. Only required if the

        "uses_savepoints" feature is True. The "sid" parameter is a string

        for the savepoint id.

        """

        raise NotImplementedError



    def savepoint_commit_sql(self, sid):

        """

        Returns the SQL for committing the given savepoint.

        """

        raise NotImplementedError



    def savepoint_rollback_sql(self, sid):

        """

        Returns the SQL for rolling back the given savepoint.

        """

        raise NotImplementedError



    def sql_flush(self, style, tables, sequences):

        """

        Returns a list of SQL statements required to remove all data from
@@ -394,7 +430,6 @@ class BaseDatabaseIntrospection(object): 


        return sequence_list



        

class BaseDatabaseClient(object):

    """

    This class encapsualtes all backend-specific methods for opening a

django/db/backends/postgresql/base.py

+5 −2
Original line number Diff line number Diff line
@@ -63,6 +63,9 @@ class UnicodeCursorWrapper(object): 
    def __iter__(self):

        return iter(self.cursor)



class DatabaseFeatures(BaseDatabaseFeatures):

    uses_savepoints = True



class DatabaseWrapper(BaseDatabaseWrapper):

    operators = {

        'exact': '= %s',
@@ -84,7 +87,7 @@ class DatabaseWrapper(BaseDatabaseWrapper): 
    def __init__(self, *args, **kwargs):

        super(DatabaseWrapper, self).__init__(*args, **kwargs)



        self.features = BaseDatabaseFeatures()

        self.features = DatabaseFeatures()

        self.ops = DatabaseOperations()

        self.client = DatabaseClient()

        self.creation = DatabaseCreation(self)

django/db/backends/postgresql/operations.py

+10 −0
Original line number Diff line number Diff line
@@ -124,3 +124,13 @@ class DatabaseOperations(BaseDatabaseOperations): 
                    style.SQL_KEYWORD('FROM'),

                    style.SQL_TABLE(qn(f.m2m_db_table()))))

        return output



    def savepoint_create_sql(self, sid):

        return "SAVEPOINT %s" % sid



    def savepoint_commit_sql(self, sid):

        return "RELEASE SAVEPOINT %s" % sid



    def savepoint_rollback_sql(self, sid):

        return "ROLLBACK TO SAVEPOINT %s" % sid

django/db/backends/postgresql_psycopg2/base.py

+1 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ psycopg2.extensions.register_adapter(SafeUnicode, psycopg2.extensions.QuotedStri 


class DatabaseFeatures(BaseDatabaseFeatures):

    needs_datetime_string_cast = False

    uses_savepoints = True



class DatabaseOperations(PostgresqlDatabaseOperations):

    def last_executed_query(self, cursor, sql, params):

django/db/transaction.py

+33 −2
Original line number Diff line number Diff line
@@ -30,9 +30,10 @@ class TransactionManagementError(Exception): 
    """

    pass



# The state is a dictionary of lists. The key to the dict is the current

# The states are dictionaries of lists. The key to the dict is the current

# thread and the list is handled as a stack of values.

state = {}

savepoint_state = {}



# The dirty flag is set by *_unless_managed functions to denote that the

# code under transaction management has changed things to require a
@@ -164,6 +165,36 @@ def rollback(): 
    connection._rollback()

    set_clean()



def savepoint():

    """

    Creates a savepoint (if supported and required by the backend) inside the

    current transaction. Returns an identifier for the savepoint that will be

    used for the subsequent rollback or commit.

    """

    thread_ident = thread.get_ident()

    if thread_ident in savepoint_state:

        savepoint_state[thread_ident].append(None)

    else:

        savepoint_state[thread_ident] = [None]

    tid = str(thread_ident).replace('-', '')

    sid = "s%s_x%d" % (tid, len(savepoint_state[thread_ident]))

    connection._savepoint(sid)

    return sid



def savepoint_rollback(sid):

    """

    Rolls back the most recent savepoint (if one exists). Does nothing if

    savepoints are not supported.

    """

    connection._savepoint_rollback(sid)



def savepoint_commit(sid):

    """

    Commits the most recent savepoint (if one exists). Does nothing if

    savepoints are not supported.

    """

    connection._savepoint_commit(sid)



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# DECORATORS #

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