435 lines
13 KiB
Python
435 lines
13 KiB
Python
from collections import defaultdict
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import six
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import datetime
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import sqlalchemy as sa
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from sqlalchemy.orm import defer
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from sqlalchemy.orm.mapper import Mapper
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from sqlalchemy.orm.query import _ColumnEntity, Query
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from sqlalchemy.orm.properties import ColumnProperty
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from sqlalchemy.orm.util import AliasedInsp
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from sqlalchemy.schema import MetaData, Table, ForeignKeyConstraint
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from sqlalchemy.sql.expression import desc, asc, Label
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class QuerySorter(object):
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def __init__(self, separator='-'):
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self.entities = []
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self.labels = []
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self.separator = separator
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def inspect_labels_and_entities(self):
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for entity in self.query._entities:
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# get all label names for queries such as:
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# db.session.query(
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# Category,
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# db.func.count(Article.id).label('articles')
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# )
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if isinstance(entity, _ColumnEntity) and entity._label_name:
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self.labels.append(entity._label_name)
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else:
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self.entities.append(entity.entity_zero.class_)
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for mapper in self.query._join_entities:
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if isinstance(mapper, Mapper):
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self.entities.append(mapper.class_)
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else:
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self.entities.append(mapper)
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def assign_order_by(self, sort):
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if not sort:
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return self.query
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sort = self.parse_sort_arg(sort)
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if sort['attr'] in self.labels:
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return self.query.order_by(sort['func'](sort['attr']))
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for entity in self.entities:
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if isinstance(entity, AliasedInsp):
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if sort['entity'] and entity.name != sort['entity']:
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continue
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selectable = entity.selectable
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if sort['attr'] in selectable.c:
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attr = selectable.c[sort['attr']]
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return self.query.order_by(sort['func'](attr))
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else:
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table = entity.__table__
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if sort['entity'] and table.name != sort['entity']:
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continue
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return self.assign_entity_attr_order_by(entity, sort)
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return self.query
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def assign_entity_attr_order_by(self, entity, sort):
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if sort['attr'] in entity.__mapper__.class_manager.keys():
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try:
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attr = getattr(entity, sort['attr'])
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except AttributeError:
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pass
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else:
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property_ = attr.property
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if isinstance(property_, ColumnProperty):
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if isinstance(attr.property.columns[0], Label):
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attr = attr.property.columns[0].name
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return self.query.order_by(sort['func'](attr))
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return self.query
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def parse_sort_arg(self, arg):
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if arg[0] == self.separator:
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func = desc
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arg = arg[1:]
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else:
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func = asc
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parts = arg.split(self.separator)
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return {
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'entity': parts[0] if len(parts) > 1 else None,
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'attr': parts[1] if len(parts) > 1 else arg,
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'func': func
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}
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def __call__(self, query, *args):
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self.query = query
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self.inspect_labels_and_entities()
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for sort in args:
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self.query = self.assign_order_by(sort)
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return self.query
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def sort_query(query, *args):
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"""
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Applies an sql ORDER BY for given query. This function can be easily used
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with user-defined sorting.
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The examples use the following model definition:
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>>> import sqlalchemy as sa
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>>> from sqlalchemy import create_engine
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>>> from sqlalchemy.orm import sessionmaker
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>>> from sqlalchemy.ext.declarative import declarative_base
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>>> from sqlalchemy_utils import sort_query
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>>>
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>>>
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>>> engine = create_engine(
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... 'sqlite:///'
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... )
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>>> Base = declarative_base()
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>>> Session = sessionmaker(bind=engine)
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>>> session = Session()
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>>>
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>>> class Category(Base):
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... __tablename__ = 'category'
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... id = sa.Column(sa.Integer, primary_key=True)
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... name = sa.Column(sa.Unicode(255))
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>>>
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>>> class Article(Base):
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... __tablename__ = 'article'
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... id = sa.Column(sa.Integer, primary_key=True)
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... name = sa.Column(sa.Unicode(255))
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... category_id = sa.Column(sa.Integer, sa.ForeignKey(Category.id))
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...
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... category = sa.orm.relationship(
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... Category, primaryjoin=category_id == Category.id
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... )
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1. Applying simple ascending sort
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>>> query = session.query(Article)
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>>> query = sort_query(query, 'name')
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2. Appying descending sort
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>>> query = sort_query(query, '-name')
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3. Applying sort to custom calculated label
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>>> query = session.query(
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... Category, db.func.count(Article.id).label('articles')
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... )
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>>> query = sort_query(query, 'articles')
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4. Applying sort to joined table column
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>>> query = session.query(Article).join(Article.category)
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>>> query = sort_query(query, 'category-name')
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:param query: query to be modified
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:param sort: string that defines the label or column to sort the query by
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:param errors: whether or not to raise exceptions if unknown sort column
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is passed
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"""
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return QuerySorter()(query, *args)
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def defer_except(query, columns):
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"""
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Deferred loads all columns in given query, except the ones given.
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This function is very useful when working with models with myriad of
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columns and you want to deferred load many columns.
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>>> from sqlalchemy_utils import defer_except
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>>> query = session.query(Article)
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>>> query = defer_except(Article, [Article.id, Article.name])
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:param columns: columns not to deferred load
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"""
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model = query._entities[0].entity_zero.class_
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fields = set(model._sa_class_manager.values())
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for field in fields:
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property_ = field.property
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if isinstance(property_, ColumnProperty):
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column = property_.columns[0]
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if column.name not in columns:
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query = query.options(defer(property_.key))
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return query
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def escape_like(string, escape_char='*'):
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"""
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Escapes the string paremeter used in SQL LIKE expressions
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>>> from sqlalchemy_utils import escape_like
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>>> query = session.query(User).filter(
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... User.name.ilike(escape_like('John'))
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... )
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:param string: a string to escape
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:param escape_char: escape character
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"""
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return (
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string
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.replace(escape_char, escape_char * 2)
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.replace('%', escape_char + '%')
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.replace('_', escape_char + '_')
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)
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def remove_property(class_, name):
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"""
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**Experimental function**
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Remove property from declarative class
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"""
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mapper = class_.mapper
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table = class_.__table__
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columns = class_.mapper.c
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column = columns[name]
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del columns._data[name]
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del mapper.columns[name]
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columns._all_cols.remove(column)
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mapper._cols_by_table[table].remove(column)
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mapper.class_manager.uninstrument_attribute(name)
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del mapper._props[name]
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def primary_keys(class_):
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"""
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Returns all primary keys for given declarative class.
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"""
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for column in class_.__table__.c:
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if column.primary_key:
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yield column
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def table_name(class_):
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"""
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Return table name of given declarative class.
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"""
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try:
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return class_.__tablename__
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except AttributeError:
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return class_.__table__.name
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def non_indexed_foreign_keys(metadata, engine=None):
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"""
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Finds all non indexed foreign keys from all tables of given MetaData.
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Very useful for optimizing postgresql database and finding out which
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foreign keys need indexes.
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:param metadata: MetaData object to inspect tables from
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"""
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reflected_metadata = MetaData()
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if metadata.bind is None and engine is None:
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raise Exception(
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'Either pass a metadata object with bind or '
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'pass engine as a second parameter'
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)
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constraints = defaultdict(list)
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for table_name in metadata.tables.keys():
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table = Table(
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table_name,
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reflected_metadata,
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autoload=True,
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autoload_with=metadata.bind or engine
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)
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for constraint in table.constraints:
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if not isinstance(constraint, ForeignKeyConstraint):
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continue
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if not is_indexed_foreign_key(constraint):
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constraints[table.name].append(constraint)
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return dict(constraints)
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def is_indexed_foreign_key(constraint):
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"""
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Whether or not given foreign key constraint's columns have been indexed.
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:param constraint: ForeignKeyConstraint object to check the indexes
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"""
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for index in constraint.table.indexes:
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index_column_names = set([
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column.name for column in index.columns
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])
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if index_column_names == set(constraint.columns):
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return True
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return False
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def declarative_base(model):
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"""
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Returns the declarative base for given model class.
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:param model: SQLAlchemy declarative model
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"""
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for parent in model.__bases__:
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try:
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parent.metadata
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return declarative_base(parent)
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except AttributeError:
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pass
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return model
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def is_auto_assigned_date_column(column):
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"""
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Returns whether or not given SQLAlchemy Column object's is auto assigned
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DateTime or Date.
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:param column: SQLAlchemy Column object
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"""
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return (
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(
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isinstance(column.type, sa.DateTime) or
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isinstance(column.type, sa.Date)
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)
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and
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(
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column.default or
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column.server_default or
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column.onupdate or
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column.server_onupdate
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)
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)
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def identity(obj):
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"""
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Return the identity of given sqlalchemy declarative model instance as a
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tuple. This differs from obj._sa_instance_state.identity in a way that it
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always returns the identity even if object is still in transient state (
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new object that is not yet persisted into database).
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:param obj: SQLAlchemy declarative model object
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"""
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id_ = []
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for attr in obj._sa_class_manager.values():
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prop = attr.property
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if isinstance(prop, sa.orm.ColumnProperty):
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column = prop.columns[0]
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if column.primary_key:
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id_.append(getattr(obj, column.name))
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return tuple(id_)
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def render_statement(statement, bind=None):
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"""
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Generate an SQL expression string with bound parameters rendered inline
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for the given SQLAlchemy statement.
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"""
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if isinstance(statement, Query):
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if bind is None:
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bind = statement.session.get_bind(statement._mapper_zero_or_none())
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statement = statement.statement
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elif bind is None:
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bind = statement.bind
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class Compiler(bind.dialect.statement_compiler):
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def visit_bindparam(self, bindparam, *args, **kwargs):
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return self.render_literal_value(bindparam.value, bindparam.type)
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def render_literal_value(self, value, type_):
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if isinstance(value, six.integer_types):
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return str(value)
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elif isinstance(value, (datetime.date, datetime.datetime)):
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return "'%s'" % value
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return super(Compiler, self).render_literal_value(value, type_)
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return Compiler(bind.dialect, statement).process(statement)
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from sqlalchemy.orm.session import object_session
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from sqlalchemy.orm import RelationshipProperty
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from sqlalchemy.orm.attributes import set_committed_value
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def batch_fetch(entities, attr):
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if entities:
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first = entities[0]
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if isinstance(attr, six.string_types):
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attr = getattr(
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first.__class__, attr
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)
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prop = attr.property
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if not isinstance(prop, RelationshipProperty):
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raise Exception(
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'Given attribute is not a relationship property.'
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)
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model = prop.mapper.class_
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session = object_session(first)
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if len(prop.remote_side) > 1:
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raise Exception(
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'Only relationships with single remote side columns are '
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'supported.'
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)
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column_name = list(prop.remote_side)[0].name
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parent_ids = [entity.id for entity in entities]
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related_entities = (
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session.query(model)
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.filter(
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getattr(model, column_name).in_(parent_ids)
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)
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)
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parent_dict = dict((entity.id, []) for entity in entities)
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for entity in related_entities:
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parent_dict[getattr(entity, column_name)].append(entity)
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for entity in entities:
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set_committed_value(entity, prop.key, parent_dict[entity.id])
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