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https://github.com/janeczku/calibre-web
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527 lines
19 KiB
Python
527 lines
19 KiB
Python
# engine/reflection.py
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# Copyright (C) 2005-2013 the SQLAlchemy authors and contributors <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""Provides an abstraction for obtaining database schema information.
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Usage Notes:
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Here are some general conventions when accessing the low level inspector
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methods such as get_table_names, get_columns, etc.
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1. Inspector methods return lists of dicts in most cases for the following
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reasons:
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* They're both standard types that can be serialized.
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* Using a dict instead of a tuple allows easy expansion of attributes.
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* Using a list for the outer structure maintains order and is easy to work
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with (e.g. list comprehension [d['name'] for d in cols]).
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2. Records that contain a name, such as the column name in a column record
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use the key 'name'. So for most return values, each record will have a
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'name' attribute..
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"""
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from .. import exc, sql
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from .. import schema as sa_schema
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from .. import util
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from ..types import TypeEngine
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from ..util import deprecated
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from ..util import topological
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from .. import inspection
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from .base import Connectable
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@util.decorator
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def cache(fn, self, con, *args, **kw):
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info_cache = kw.get('info_cache', None)
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if info_cache is None:
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return fn(self, con, *args, **kw)
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key = (
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fn.__name__,
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tuple(a for a in args if isinstance(a, basestring)),
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tuple((k, v) for k, v in kw.iteritems() if isinstance(v, (basestring, int, float)))
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)
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ret = info_cache.get(key)
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if ret is None:
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ret = fn(self, con, *args, **kw)
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info_cache[key] = ret
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return ret
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class Inspector(object):
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"""Performs database schema inspection.
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The Inspector acts as a proxy to the reflection methods of the
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:class:`~sqlalchemy.engine.interfaces.Dialect`, providing a
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consistent interface as well as caching support for previously
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fetched metadata.
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A :class:`.Inspector` object is usually created via the
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:func:`.inspect` function::
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from sqlalchemy import inspect, create_engine
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engine = create_engine('...')
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insp = inspect(engine)
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The inspection method above is equivalent to using the
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:meth:`.Inspector.from_engine` method, i.e.::
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engine = create_engine('...')
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insp = Inspector.from_engine(engine)
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Where above, the :class:`~sqlalchemy.engine.interfaces.Dialect` may opt
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to return an :class:`.Inspector` subclass that provides additional
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methods specific to the dialect's target database.
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"""
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def __init__(self, bind):
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"""Initialize a new :class:`.Inspector`.
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:param bind: a :class:`~sqlalchemy.engine.Connectable`,
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which is typically an instance of
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:class:`~sqlalchemy.engine.Engine` or
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:class:`~sqlalchemy.engine.Connection`.
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For a dialect-specific instance of :class:`.Inspector`, see
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:meth:`.Inspector.from_engine`
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"""
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# this might not be a connection, it could be an engine.
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self.bind = bind
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# set the engine
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if hasattr(bind, 'engine'):
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self.engine = bind.engine
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else:
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self.engine = bind
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if self.engine is bind:
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# if engine, ensure initialized
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bind.connect().close()
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self.dialect = self.engine.dialect
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self.info_cache = {}
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@classmethod
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def from_engine(cls, bind):
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"""Construct a new dialect-specific Inspector object from the given
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engine or connection.
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:param bind: a :class:`~sqlalchemy.engine.Connectable`,
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which is typically an instance of
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:class:`~sqlalchemy.engine.Engine` or
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:class:`~sqlalchemy.engine.Connection`.
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This method differs from direct a direct constructor call of
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:class:`.Inspector` in that the
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:class:`~sqlalchemy.engine.interfaces.Dialect` is given a chance to
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provide a dialect-specific :class:`.Inspector` instance, which may
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provide additional methods.
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See the example at :class:`.Inspector`.
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"""
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if hasattr(bind.dialect, 'inspector'):
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return bind.dialect.inspector(bind)
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return Inspector(bind)
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@inspection._inspects(Connectable)
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def _insp(bind):
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return Inspector.from_engine(bind)
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@property
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def default_schema_name(self):
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"""Return the default schema name presented by the dialect
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for the current engine's database user.
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E.g. this is typically ``public`` for Postgresql and ``dbo``
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for SQL Server.
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"""
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return self.dialect.default_schema_name
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def get_schema_names(self):
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"""Return all schema names.
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"""
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if hasattr(self.dialect, 'get_schema_names'):
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return self.dialect.get_schema_names(self.bind,
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info_cache=self.info_cache)
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return []
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def get_table_names(self, schema=None, order_by=None):
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"""Return all table names in referred to within a particular schema.
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The names are expected to be real tables only, not views.
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Views are instead returned using the :meth:`.get_view_names`
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method.
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:param schema: Schema name. If ``schema`` is left at ``None``, the
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database's default schema is
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used, else the named schema is searched. If the database does not
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support named schemas, behavior is undefined if ``schema`` is not
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passed as ``None``.
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:param order_by: Optional, may be the string "foreign_key" to sort
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the result on foreign key dependencies.
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.. versionchanged:: 0.8 the "foreign_key" sorting sorts tables
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in order of dependee to dependent; that is, in creation
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order, rather than in drop order. This is to maintain
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consistency with similar features such as
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:attr:`.MetaData.sorted_tables` and :func:`.util.sort_tables`.
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.. seealso::
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:attr:`.MetaData.sorted_tables`
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"""
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if hasattr(self.dialect, 'get_table_names'):
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tnames = self.dialect.get_table_names(self.bind,
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schema, info_cache=self.info_cache)
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else:
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tnames = self.engine.table_names(schema)
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if order_by == 'foreign_key':
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tuples = []
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for tname in tnames:
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for fkey in self.get_foreign_keys(tname, schema):
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if tname != fkey['referred_table']:
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tuples.append((fkey['referred_table'], tname))
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tnames = list(topological.sort(tuples, tnames))
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return tnames
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def get_table_options(self, table_name, schema=None, **kw):
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"""Return a dictionary of options specified when the table of the
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given name was created.
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This currently includes some options that apply to MySQL tables.
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"""
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if hasattr(self.dialect, 'get_table_options'):
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return self.dialect.get_table_options(
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self.bind, table_name, schema,
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info_cache=self.info_cache, **kw)
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return {}
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def get_view_names(self, schema=None):
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"""Return all view names in `schema`.
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:param schema: Optional, retrieve names from a non-default schema.
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"""
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return self.dialect.get_view_names(self.bind, schema,
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info_cache=self.info_cache)
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def get_view_definition(self, view_name, schema=None):
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"""Return definition for `view_name`.
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:param schema: Optional, retrieve names from a non-default schema.
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"""
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return self.dialect.get_view_definition(
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self.bind, view_name, schema, info_cache=self.info_cache)
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def get_columns(self, table_name, schema=None, **kw):
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"""Return information about columns in `table_name`.
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Given a string `table_name` and an optional string `schema`, return
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column information as a list of dicts with these keys:
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name
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the column's name
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type
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:class:`~sqlalchemy.types.TypeEngine`
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nullable
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boolean
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default
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the column's default value
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attrs
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dict containing optional column attributes
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"""
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col_defs = self.dialect.get_columns(self.bind, table_name, schema,
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info_cache=self.info_cache,
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**kw)
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for col_def in col_defs:
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# make this easy and only return instances for coltype
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coltype = col_def['type']
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if not isinstance(coltype, TypeEngine):
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col_def['type'] = coltype()
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return col_defs
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@deprecated('0.7', 'Call to deprecated method get_primary_keys.'
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' Use get_pk_constraint instead.')
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def get_primary_keys(self, table_name, schema=None, **kw):
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"""Return information about primary keys in `table_name`.
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Given a string `table_name`, and an optional string `schema`, return
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primary key information as a list of column names.
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"""
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return self.dialect.get_pk_constraint(self.bind, table_name, schema,
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info_cache=self.info_cache,
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**kw)['constrained_columns']
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def get_pk_constraint(self, table_name, schema=None, **kw):
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"""Return information about primary key constraint on `table_name`.
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Given a string `table_name`, and an optional string `schema`, return
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primary key information as a dictionary with these keys:
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constrained_columns
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a list of column names that make up the primary key
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name
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optional name of the primary key constraint.
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"""
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return self.dialect.get_pk_constraint(self.bind, table_name, schema,
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info_cache=self.info_cache,
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**kw)
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def get_foreign_keys(self, table_name, schema=None, **kw):
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"""Return information about foreign_keys in `table_name`.
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Given a string `table_name`, and an optional string `schema`, return
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foreign key information as a list of dicts with these keys:
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constrained_columns
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a list of column names that make up the foreign key
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referred_schema
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the name of the referred schema
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referred_table
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the name of the referred table
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referred_columns
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a list of column names in the referred table that correspond to
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constrained_columns
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name
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optional name of the foreign key constraint.
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\**kw
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other options passed to the dialect's get_foreign_keys() method.
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"""
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return self.dialect.get_foreign_keys(self.bind, table_name, schema,
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info_cache=self.info_cache,
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**kw)
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def get_indexes(self, table_name, schema=None, **kw):
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"""Return information about indexes in `table_name`.
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Given a string `table_name` and an optional string `schema`, return
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index information as a list of dicts with these keys:
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name
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the index's name
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column_names
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list of column names in order
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unique
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boolean
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\**kw
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other options passed to the dialect's get_indexes() method.
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"""
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return self.dialect.get_indexes(self.bind, table_name,
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schema,
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info_cache=self.info_cache, **kw)
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def reflecttable(self, table, include_columns, exclude_columns=()):
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"""Given a Table object, load its internal constructs based on
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introspection.
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This is the underlying method used by most dialects to produce
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table reflection. Direct usage is like::
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from sqlalchemy import create_engine, MetaData, Table
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from sqlalchemy.engine import reflection
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engine = create_engine('...')
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meta = MetaData()
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user_table = Table('user', meta)
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insp = Inspector.from_engine(engine)
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insp.reflecttable(user_table, None)
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:param table: a :class:`~sqlalchemy.schema.Table` instance.
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:param include_columns: a list of string column names to include
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in the reflection process. If ``None``, all columns are reflected.
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"""
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dialect = self.bind.dialect
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# table attributes we might need.
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reflection_options = dict(
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(k, table.kwargs.get(k))
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for k in dialect.reflection_options if k in table.kwargs)
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schema = table.schema
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table_name = table.name
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# apply table options
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tbl_opts = self.get_table_options(table_name, schema, **table.kwargs)
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if tbl_opts:
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table.kwargs.update(tbl_opts)
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# table.kwargs will need to be passed to each reflection method. Make
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# sure keywords are strings.
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tblkw = table.kwargs.copy()
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for (k, v) in tblkw.items():
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del tblkw[k]
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tblkw[str(k)] = v
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# Py2K
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if isinstance(schema, str):
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schema = schema.decode(dialect.encoding)
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if isinstance(table_name, str):
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table_name = table_name.decode(dialect.encoding)
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# end Py2K
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# columns
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found_table = False
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cols_by_orig_name = {}
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for col_d in self.get_columns(table_name, schema, **tblkw):
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found_table = True
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orig_name = col_d['name']
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table.dispatch.column_reflect(self, table, col_d)
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name = col_d['name']
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if include_columns and name not in include_columns:
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continue
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if exclude_columns and name in exclude_columns:
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continue
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coltype = col_d['type']
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col_kw = {
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'nullable': col_d['nullable'],
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}
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for k in ('autoincrement', 'quote', 'info', 'key'):
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if k in col_d:
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col_kw[k] = col_d[k]
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colargs = []
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if col_d.get('default') is not None:
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# the "default" value is assumed to be a literal SQL
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# expression, so is wrapped in text() so that no quoting
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# occurs on re-issuance.
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colargs.append(
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sa_schema.DefaultClause(
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sql.text(col_d['default']), _reflected=True
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)
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)
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if 'sequence' in col_d:
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# TODO: mssql, maxdb and sybase are using this.
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seq = col_d['sequence']
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sequence = sa_schema.Sequence(seq['name'], 1, 1)
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if 'start' in seq:
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sequence.start = seq['start']
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if 'increment' in seq:
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sequence.increment = seq['increment']
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colargs.append(sequence)
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cols_by_orig_name[orig_name] = col = \
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sa_schema.Column(name, coltype, *colargs, **col_kw)
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table.append_column(col)
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if not found_table:
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raise exc.NoSuchTableError(table.name)
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# Primary keys
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pk_cons = self.get_pk_constraint(table_name, schema, **tblkw)
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if pk_cons:
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pk_cols = [
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cols_by_orig_name[pk]
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for pk in pk_cons['constrained_columns']
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if pk in cols_by_orig_name and pk not in exclude_columns
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]
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pk_cols += [
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pk
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for pk in table.primary_key
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if pk.key in exclude_columns
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]
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primary_key_constraint = sa_schema.PrimaryKeyConstraint(
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name=pk_cons.get('name'),
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*pk_cols
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)
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table.append_constraint(primary_key_constraint)
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# Foreign keys
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fkeys = self.get_foreign_keys(table_name, schema, **tblkw)
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for fkey_d in fkeys:
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conname = fkey_d['name']
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# look for columns by orig name in cols_by_orig_name,
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# but support columns that are in-Python only as fallback
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constrained_columns = [
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cols_by_orig_name[c].key
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if c in cols_by_orig_name else c
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for c in fkey_d['constrained_columns']
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]
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if exclude_columns and set(constrained_columns).intersection(
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exclude_columns):
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continue
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referred_schema = fkey_d['referred_schema']
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referred_table = fkey_d['referred_table']
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referred_columns = fkey_d['referred_columns']
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refspec = []
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if referred_schema is not None:
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sa_schema.Table(referred_table, table.metadata,
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autoload=True, schema=referred_schema,
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autoload_with=self.bind,
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**reflection_options
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)
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for column in referred_columns:
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refspec.append(".".join(
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[referred_schema, referred_table, column]))
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else:
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sa_schema.Table(referred_table, table.metadata, autoload=True,
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autoload_with=self.bind,
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**reflection_options
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)
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for column in referred_columns:
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refspec.append(".".join([referred_table, column]))
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table.append_constraint(
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sa_schema.ForeignKeyConstraint(constrained_columns, refspec,
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conname, link_to_name=True))
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# Indexes
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indexes = self.get_indexes(table_name, schema)
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for index_d in indexes:
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name = index_d['name']
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columns = index_d['column_names']
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unique = index_d['unique']
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flavor = index_d.get('type', 'unknown type')
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if include_columns and \
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not set(columns).issubset(include_columns):
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util.warn(
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"Omitting %s KEY for (%s), key covers omitted columns." %
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(flavor, ', '.join(columns)))
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continue
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# look for columns by orig name in cols_by_orig_name,
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# but support columns that are in-Python only as fallback
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sa_schema.Index(name, *[
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cols_by_orig_name[c] if c in cols_by_orig_name
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else table.c[c]
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for c in columns
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],
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**dict(unique=unique))
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