[Sqlalchemy-tickets] [sqlalchemy] #2946: Redshift support

[sqlalchemy <mi...@zz...>]

#2946: Redshift support
-----------------------------+-----------------------------------------
 Reporter:  KyleJamesWalker  |           Owner:  zzzeek
     Type:  defect           |          Status:  new
 Priority:  medium           |       Milestone:
Component:  postgres         |        Severity:  no triage selected yet
 Keywords:                   |  Progress State:  awaiting triage
-----------------------------+-----------------------------------------
 SQLAlchemy 9.1 does not support connecting to RedShfit because of the
 change in dialects/postgresql/base.py:
 {{{
 class PGDialect(default.DefaultDialect):
     ...
     def initialize(self, connection):
         ...
         self._backslash_escapes = connection.scalar(
                                     "show standard_conforming_strings"
                                     ) == 'off'
 }}}

 This crashes because there is no standard_conforming_string defined in
 redshift.  I think this check needs to be added "self.server_version_info
 >= (8, 2)", as the documentation for postgres starts mentioning this in
 8.2.
    http://www.postgresql.org/docs/8.2/static/runtime-config-
 compatible.html

 This was working on older versions of SQLAlchemy but I need to also
 connect to a postgres 9.3 db in my app, so I needed to upgrade.

 For now I've made a simple work around:

 Register the dialect in my app:
 {{{
 from sqlalchemy.dialects import registry
 registry.register("redshift", "myapp.dialects.redshift",
 "RedShiftDialect")
 }}}

 Define a new dialect in my app:
 {{{
 from sqlalchemy.dialects.postgresql.base import ENUM
 from sqlalchemy.dialects.postgresql.psycopg2 import PGDialect_psycopg2
 from sqlalchemy import types as sqltypes


 class RedShiftDialect(PGDialect_psycopg2):
     def initialize(self, connection):
         # Don't call super, it will crash, manually copying code that
 super would call
         #super(PGDialect, self).initialize(connection)
         self.implicit_returning = self.server_version_info > (8, 2) and \
             self.__dict__.get('implicit_returning', True)
         self.supports_native_enum = self.server_version_info >= (8, 3)
         if not self.supports_native_enum:
             self.colspecs = self.colspecs.copy()
             # pop base Enum type
             self.colspecs.pop(sqltypes.Enum, None)
             # psycopg2, others may have placed ENUM here as well
             self.colspecs.pop(ENUM, None)

         #
 http://www.postgresql.org/docs/9.3/static/release-9-2.html#AEN116689
         self.supports_smallserial = self.server_version_info >= (9, 2)

         # This breaks redshift, if a version check was here or exception
         # protection the RedShiftDialect would not be needed
         ###Suggest Adding Check: if self.server_version_info >= (8, 2):
 ###
         #self._backslash_escapes = connection.scalar(
         #                            "show standard_conforming_strings"
         #                            ) == 'off'

         # Don't call super, it will crash, manually copying code that
 super would call
         #super(PGDialect_psycopg2, self).initialize(connection)
         self._has_native_hstore = self.use_native_hstore and \
             self._hstore_oids(connection.connection) is not None
         self._has_native_json = self.psycopg2_version >= (2, 5)
 }}}

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Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2946>
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