[DRAFT] First roughly working Django backend

buildout.cfg

@@ -9,16 +9,18 @@ parts = test
  scripts
  sphinx
 
+[tox]
+recipe = zc.recipe.egg:script
+eggs = tox
+ crate [test,sqlalchemy,django]
+ setuptools
+
 [scripts]
 recipe = zc.recipe.egg:script
 interpreter = py
 eggs = crate
  wheel
 
-[tox]
-recipe = zc.recipe.egg:script
-eggs = tox
-
 [crate]
 recipe = hexagonit.recipe.download
 url = https://cdn.crate.io/downloads/releases/crate-${versions:crate_server}.tar.gz

setup.py

@@ -75,7 +75,8 @@ def read(path):
  'mock>=1.0.1',
  'zope.testing',
  'zc.customdoctests>=1.0.1'],
- sqlalchemy=['sqlalchemy>=0.8.2']
+ sqlalchemy=['sqlalchemy>=0.8.2'],
+ django=['django>=1.6,<1.7']
  ),
  install_requires=requirements,
  package_data={'': ['*.txt']},

src/crate/client/connection.py

@@ -59,6 +59,13 @@ def commit(self):
  if self._closed:
  raise ProgrammingError("Connection closed")
 
+ def rollback(self):
+ """
+ Transactions are not supported, so ``rollback`` is not implemented.
+ """
+ if self._closed:
+ raise ProgrammingError("Connection closed")
+
  def get_blob_container(self, container_name):
  """ Retrieve a BlobContainer for `container_name`
 

src/crate/client/django/__init__.py

@@ -0,0 +1 @@
+# -*- coding: utf-8 -*-

src/crate/client/django/backend/__init__.py

@@ -0,0 +1 @@
+# -*- coding: utf-8 -*-

src/crate/client/django/backend/base.py

@@ -0,0 +1,213 @@
+# -*- coding: utf-8 -*-
+from crate.client.connection import Connection
+import crate.client.exceptions as Database
+from django.db.backends import (
+ BaseDatabaseFeatures,
+ BaseDatabaseWrapper
+)
+
+from .client import DatabaseClient
+from .operations import DatabaseOperations
+from .creation import DatabaseCreation
+from .introspection import DatabaseIntrospection
+from .validation import DatabaseValidation
+
+
+class DatabaseFeatures(BaseDatabaseFeatures):
+ # Does the backend distinguish between '' and None?
+ interprets_empty_strings_as_nulls = False
+
+ allows_group_by_pk = True
+ # True if django.db.backend.utils.typecast_timestamp is used on values
+ # returned from dates() calls.
+ needs_datetime_string_cast = False
+ update_can_self_select = True
+
+ can_use_chunked_reads = False
+ can_return_id_from_insert = False
+ has_bulk_insert = False
+ uses_savepoints = False
+ can_combine_inserts_with_and_without_auto_increment_pk = False
+
+ # If True, don't use integer foreign keys referring to, e.g., positive
+ # integer primary keys.
+ related_fields_match_type = False
+ allow_sliced_subqueries = False
+ has_select_for_update = False
+ has_select_for_update_nowait = False
+
+ supports_select_related = False
+
+ # Does the default test database allow multiple connections?
+ # Usually an indication that the test database is in-memory
+ test_db_allows_multiple_connections = True
+
+ # Can an object be saved without an explicit primary key?
+ supports_unspecified_pk = False
+
+ # Can a fixture contain forward references? i.e., are
+ # FK constraints checked at the end of transaction, or
+ # at the end of each save operation?
+ supports_forward_references = False
+
+ # Does a dirty transaction need to be rolled back
+ # before the cursor can be used again?
+ requires_rollback_on_dirty_transaction = False
+
+ # Does the backend allow very long model names without error?
+ supports_long_model_names = True
+
+ # Is there a REAL datatype in addition to floats/doubles?
+ has_real_datatype = False
+ supports_subqueries_in_group_by = False
+ supports_bitwise_or = False
+
+ # Do time/datetime fields have microsecond precision?
+ supports_microsecond_precision = True
+
+ # Does the __regex lookup support backreferencing and grouping?
+ supports_regex_backreferencing = False
+
+ # Can date/datetime lookups be performed using a string?
+ supports_date_lookup_using_string = True
+
+ # Can datetimes with timezones be used?
+ supports_timezones = False
+
+ # Does the database have a copy of the zoneinfo database?
+ has_zoneinfo_database = False
+
+ # When performing a GROUP BY, is an ORDER BY NULL required
+ # to remove any ordering?
+ requires_explicit_null_ordering_when_grouping = False
+
+ # Can an object have a primary key of 0? MySQL says No.
+ allows_primary_key_0 = True
+
+ # Do we need to NULL a ForeignKey out, or can the constraint check be
+ # deferred
+ can_defer_constraint_checks = False
+
+ # date_interval_sql can properly handle mixed Date/DateTime fields and timedeltas
+ supports_mixed_date_datetime_comparisons = True
+
+ # Does the backend support tablespaces? Default to False because it isn't
+ # in the SQL standard.
+ supports_tablespaces = False
+
+ # Does the backend reset sequences between tests?
+ supports_sequence_reset = False
+
+ # Confirm support for introspected foreign keys
+ # Every database can do this reliably, except MySQL,
+ # which can't do it for MyISAM tables
+ can_introspect_foreign_keys = False
+
+ # Support for the DISTINCT ON clause
+ can_distinct_on_fields = False
+
+ # Does the backend decide to commit before SAVEPOINT statements
+ # when autocommit is disabled? http://bugs.python.org/issue8145#msg109965
+ autocommits_when_autocommit_is_off = False
+
+ # Does the backend prevent running SQL queries in broken transactions?
+ atomic_transactions = False
+
+ # Does the backend support 'pyformat' style ("... %(name)s ...", {'name': value})
+ # parameter passing? Note this can be provided by the backend even if not
+ # supported by the Python driver
+ supports_paramstyle_pyformat = False
+
+
+class DatabaseWrapper(BaseDatabaseWrapper):
+
+ vendor = 'crate'
+ operators = {
+ 'exact': '= %s',
+ 'iexact': '= %s',
+ 'contains': 'LIKE %s',
+ 'icontains': 'LIKE %s',
+ 'regex': '%s',
+ 'iregex': '%s',
+ 'gt': '> %s',
+ 'gte': '>= %s',
+ 'lt': '< %s',
+ 'lte': '<= %s',
+ 'startswith': 'LIKE %s',
+ 'endswith': 'LIKE %s',
+ 'istartswith': 'LIKE %s',
+ 'iendswith': 'LIKE %s',
+ }
+
+ Database = Database
+
+ def __init__(self, *args, **kwargs):
+ super(DatabaseWrapper, self).__init__(*args, **kwargs)
+
+ self.features = DatabaseFeatures(self)
+ self.ops = DatabaseOperations(self)
+ self.client = DatabaseClient(self)
+ self.creation = DatabaseCreation(self)
+ self.introspection = DatabaseIntrospection(self)
+ self.validation = DatabaseValidation(self)
+
+ ### CREATING CONNECTIONS AND CURSORS
+
+ def get_connection_params(self):
+ """Returns a dict of parameters suitable for get_new_connection."""
+ servers = self.settings_dict.get("SERVERS", ["localhost:4200"])
+ timeout = self.settings_dict.get("TIMEOUT", None)
+ return {
+ "servers": servers,
+ "timeout": timeout
+ }
+
+ def get_new_connection(self, conn_params):
+ """Opens a connection to the database."""
+ return Connection(**conn_params)
+
+ def init_connection_state(self):
+ """Initializes the database connection settings."""
+ pass
+
+ def create_cursor(self):
+ """Creates a cursor. Assumes that a connection is established."""
+ return self.connection.cursor()
+
+ ### COMMIT
+ def _commit(self):
+ pass
+ # TODO: refresh?
+ # if self.connection is not None:
+ # with self.wrap_database_errors:
+ # self.connection.client.
+
+ ### SAVEPOINT STUFF NOT SUPPORTED
+
+ def _savepoint(self, sid):
+ pass
+
+ def _savepoint_rollback(self, sid):
+ pass
+
+ def _savepoint_commit(self, sid):
+ pass
+
+ def _savepoint_allowed(self):
+ return False
+
+ ### AUTOCOMMIT NOT SUPPORTED
+
+ def _set_autocommit(self, autocommit):
+ pass
+
+ ### TEST IF CONNECTION IS USABLE
+
+ def is_usable(self):
+ """check if connection works"""
+ try:
+ self.connection.client._json_request("GET", "/")
+ except:
+ return False
+ else:
+ return True

src/crate/client/django/backend/client.py

@@ -0,0 +1,15 @@
+# -*- coding: utf-8 -*-
+from django.db.backends import BaseDatabaseClient
+from crate.client.crash import main as crash_main
+
+
+class DatabaseClient(BaseDatabaseClient):
+ executable_name = 'crash'
+
+ def runshell(self):
+ """TODO: run shell"""
+ settings_dict = self.connection.settings_dict
+
+ import sys
+ sys.argv = [sys.argv[0], "--hosts", settings_dict['SERVERS']]
+ crash_main()

src/crate/client/django/backend/compiler.py

@@ -0,0 +1,44 @@
+# -*- coding: utf-8 -*-
+
+from django.db.models.sql import compiler
+
+
+class SQLCompiler(compiler.SQLCompiler):
+
+ def as_sql(self, with_limits=True, with_col_aliases=False):
+ sql, params = super(SQLCompiler, self).as_sql(with_limits=with_limits, with_col_aliases=with_col_aliases)
+ return sql.replace("%s", "?"), params
+
+
+class SQLInsertCompiler(compiler.SQLInsertCompiler, SQLCompiler):
+ pass
+
+
+class SQLDeleteCompiler(compiler.SQLDeleteCompiler, SQLCompiler):
+ def as_sql(self):
+ """
+ hack for converting djangos arguments placeholders into question marks
+ as crate-python uses dbapi option ``paramstyle=qmark`` which is not supported by
+ django
+
+ TODO: make a Pull Request for django to support this dbapi option
+ :return: tuple of (<sql-statement>, <list of params>)
+ """
+ sql, params = super(SQLDeleteCompiler, self).as_sql()
+ return sql.replace("%s", "?"), params
+
+
+class SQLUpdateCompiler(compiler.SQLUpdateCompiler, SQLCompiler):
+ pass
+
+
+class SQLAggregateCompiler(compiler.SQLAggregateCompiler, SQLCompiler):
+ pass
+
+
+class SQLDateCompiler(compiler.SQLDateCompiler, SQLCompiler):
+ pass
+
+
+class SQLDateTimeCompiler(compiler.SQLDateTimeCompiler, SQLCompiler):
+ pass