/usr/lib/python2.7/dist-packages/sqlalchemy_utils/functions/database.py is in python-sqlalchemy-utils 0.30.12-4.
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import itertools
import os
from copy import copy
import sqlalchemy as sa
from sqlalchemy.engine.url import make_url
from sqlalchemy.exc import OperationalError, ProgrammingError
from sqlalchemy_utils.expressions import explain_analyze
from .orm import quote
class PlanAnalysis(object):
def __init__(self, plan):
self.plan = plan
@property
def node_types(self):
types = [self.plan['Node Type']]
if 'Plans' in self.plan:
for plan in self.plan['Plans']:
analysis = PlanAnalysis(plan)
types.extend(analysis.node_types)
return types
class QueryAnalysis(object):
def __init__(self, result_set):
self.plan = result_set[0]['Plan']
if 'Total Runtime' in result_set[0]:
# PostgreSQL versions < 9.4
self.runtime = result_set[0]['Total Runtime']
else:
# PostgreSQL versions >= 9.4
self.runtime = (
result_set[0]['Execution Time'] +
result_set[0]['Planning Time']
)
@property
def node_types(self):
return list(PlanAnalysis(self.plan).node_types)
def __repr__(self):
return '<QueryAnalysis runtime=%r>' % self.runtime
def analyze(conn, query):
"""
Analyze query using given connection and return :class:`QueryAnalysis`
object. Analysis is performed using database specific EXPLAIN ANALYZE
construct and then examining the results into structured format. Currently
only PostgreSQL is supported.
Getting query runtime (in database level) ::
from sqlalchemy_utils import analyze
analysis = analyze(conn, 'SELECT * FROM article')
analysis.runtime # runtime as milliseconds
Analyze can be very useful when testing that query doesn't issue a
sequential scan (scanning all rows in table). You can for example write
simple performance tests this way.::
query = (
session.query(Article.name)
.order_by(Article.name)
.limit(10)
)
analysis = analyze(self.connection, query)
analysis.node_types # [u'Limit', u'Index Only Scan']
assert 'Seq Scan' not in analysis.node_types
.. versionadded: 0.26.17
:param conn: SQLAlchemy Connection object
:param query: SQLAlchemy Query object or query as a string
"""
return QueryAnalysis(
conn.execute(
explain_analyze(query, buffers=True, format='json')
).scalar()
)
def escape_like(string, escape_char='*'):
"""
Escape the string paremeter used in SQL LIKE expressions.
::
from sqlalchemy_utils import escape_like
query = session.query(User).filter(
User.name.ilike(escape_like('John'))
)
:param string: a string to escape
:param escape_char: escape character
"""
return (
string
.replace(escape_char, escape_char * 2)
.replace('%', escape_char + '%')
.replace('_', escape_char + '_')
)
def json_sql(value, scalars_to_json=True):
"""
Convert python data structures to PostgreSQL specific SQLAlchemy JSON
constructs. This function is extremly useful if you need to build
PostgreSQL JSON on python side.
.. note::
This function needs PostgreSQL >= 9.4
Scalars are converted to to_json SQLAlchemy function objects
::
json_sql(1) # Equals SQL: to_json(1)
json_sql('a') # to_json('a')
Mappings are converted to json_build_object constructs
::
json_sql({'a': 'c', '2': 5}) # json_build_object('a', 'c', '2', 5)
Sequences (other than strings) are converted to json_build_array constructs
::
json_sql([1, 2, 3]) # json_build_array(1, 2, 3)
You can also nest these data structures
::
json_sql({'a': [1, 2, 3]})
# json_build_object('a', json_build_array[1, 2, 3])
:param value:
value to be converted to SQLAlchemy PostgreSQL function constructs
"""
scalar_convert = sa.text
if scalars_to_json:
scalar_convert = lambda a: sa.func.to_json(sa.text(a))
if isinstance(value, collections.Mapping):
return sa.func.json_build_object(
*(
json_sql(v, scalars_to_json=False)
for v in itertools.chain(*value.items())
)
)
elif isinstance(value, str):
return scalar_convert("'{0}'".format(value))
elif isinstance(value, collections.Sequence):
return sa.func.json_build_array(
*(
json_sql(v, scalars_to_json=False)
for v in value
)
)
elif isinstance(value, (int, float)):
return scalar_convert(str(value))
return value
def has_index(column):
"""
Return whether or not given column has an index. A column has an index if
it has a single column index or it is the first column in compound column
index.
:param column: SQLAlchemy Column object
.. versionadded: 0.26.2
::
from sqlalchemy_utils import has_index
class Article(Base):
__tablename__ = 'article'
id = sa.Column(sa.Integer, primary_key=True)
title = sa.Column(sa.String(100))
is_published = sa.Column(sa.Boolean, index=True)
is_deleted = sa.Column(sa.Boolean)
is_archived = sa.Column(sa.Boolean)
__table_args__ = (
sa.Index('my_index', is_deleted, is_archived),
)
table = Article.__table__
has_index(table.c.is_published) # True
has_index(table.c.is_deleted) # True
has_index(table.c.is_archived) # False
Also supports primary key indexes
::
from sqlalchemy_utils import has_index
class ArticleTranslation(Base):
__tablename__ = 'article_translation'
id = sa.Column(sa.Integer, primary_key=True)
locale = sa.Column(sa.String(10), primary_key=True)
title = sa.Column(sa.String(100))
table = ArticleTranslation.__table__
has_index(table.c.locale) # False
has_index(table.c.id) # True
"""
table = column.table
if not isinstance(table, sa.Table):
raise TypeError(
'Only columns belonging to Table objects are supported. Given '
'column belongs to %r.' % table
)
primary_keys = table.primary_key.columns.values()
return (
(primary_keys and column is primary_keys[0])
or
any(
index.columns.values()[0] is column
for index in table.indexes
)
)
def has_unique_index(column):
"""
Return whether or not given column has a unique index. A column has a
unique index if it has a single column primary key index or it has a
single column UniqueConstraint.
:param column: SQLAlchemy Column object
.. versionadded: 0.27.1
::
from sqlalchemy_utils import has_unique_index
class Article(Base):
__tablename__ = 'article'
id = sa.Column(sa.Integer, primary_key=True)
title = sa.Column(sa.String(100))
is_published = sa.Column(sa.Boolean, unique=True)
is_deleted = sa.Column(sa.Boolean)
is_archived = sa.Column(sa.Boolean)
table = Article.__table__
has_unique_index(table.c.is_published) # True
has_unique_index(table.c.is_deleted) # False
has_unique_index(table.c.id) # True
:raises TypeError: if given column does not belong to a Table object
"""
table = column.table
if not isinstance(table, sa.Table):
raise TypeError(
'Only columns belonging to Table objects are supported. Given '
'column belongs to %r.' % table
)
pks = table.primary_key.columns
return (
(column is pks.values()[0] and len(pks) == 1)
or
any(
match_columns(constraint.columns.values()[0], column) and
len(constraint.columns) == 1
for constraint in column.table.constraints
if isinstance(constraint, sa.sql.schema.UniqueConstraint)
)
)
def match_columns(column, column2):
return column.table is column2.table and column.name == column2.name
def is_auto_assigned_date_column(column):
"""
Returns whether or not given SQLAlchemy Column object's is auto assigned
DateTime or Date.
:param column: SQLAlchemy Column object
"""
return (
(
isinstance(column.type, sa.DateTime) or
isinstance(column.type, sa.Date)
)
and
(
column.default or
column.server_default or
column.onupdate or
column.server_onupdate
)
)
def database_exists(url):
"""Check if a database exists.
:param url: A SQLAlchemy engine URL.
Performs backend-specific testing to quickly determine if a database
exists on the server. ::
database_exists('postgres://postgres@localhost/name') #=> False
create_database('postgres://postgres@localhost/name')
database_exists('postgres://postgres@localhost/name') #=> True
Supports checking against a constructed URL as well. ::
engine = create_engine('postgres://postgres@localhost/name')
database_exists(engine.url) #=> False
create_database(engine.url)
database_exists(engine.url) #=> True
"""
url = copy(make_url(url))
database = url.database
if url.drivername.startswith('postgresql'):
url.database = 'template1'
else:
url.database = None
engine = sa.create_engine(url)
if engine.dialect.name == 'postgresql':
text = "SELECT 1 FROM pg_database WHERE datname='%s'" % database
return bool(engine.execute(text).scalar())
elif engine.dialect.name == 'mysql':
text = ("SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA "
"WHERE SCHEMA_NAME = '%s'" % database)
return bool(engine.execute(text).scalar())
elif engine.dialect.name == 'sqlite':
return database == ':memory:' or os.path.exists(database)
else:
text = 'SELECT 1'
try:
url.database = database
engine = sa.create_engine(url)
engine.execute(text)
return True
except (ProgrammingError, OperationalError):
return False
def create_database(url, encoding='utf8', template=None):
"""Issue the appropriate CREATE DATABASE statement.
:param url: A SQLAlchemy engine URL.
:param encoding: The encoding to create the database as.
:param template:
The name of the template from which to create the new database. At the
moment only supported by PostgreSQL driver.
To create a database, you can pass a simple URL that would have
been passed to ``create_engine``. ::
create_database('postgres://postgres@localhost/name')
You may also pass the url from an existing engine. ::
create_database(engine.url)
Has full support for mysql, postgres, and sqlite. In theory,
other database engines should be supported.
"""
url = copy(make_url(url))
database = url.database
if url.drivername.startswith('postgresql'):
url.database = 'template1'
elif not url.drivername.startswith('sqlite'):
url.database = None
engine = sa.create_engine(url)
if engine.dialect.name == 'postgresql':
if engine.driver == 'psycopg2':
from psycopg2.extensions import ISOLATION_LEVEL_AUTOCOMMIT
engine.raw_connection().set_isolation_level(
ISOLATION_LEVEL_AUTOCOMMIT
)
if not template:
template = 'template0'
text = "CREATE DATABASE {0} ENCODING '{1}' TEMPLATE {2}".format(
quote(engine, database),
encoding,
quote(engine, template)
)
engine.execute(text)
elif engine.dialect.name == 'mysql':
text = "CREATE DATABASE {0} CHARACTER SET = '{1}'".format(
quote(engine, database),
encoding
)
engine.execute(text)
elif engine.dialect.name == 'sqlite' and database != ':memory:':
open(database, 'w').close()
else:
text = 'CREATE DATABASE {0}'.format(quote(engine, database))
engine.execute(text)
def drop_database(url):
"""Issue the appropriate DROP DATABASE statement.
:param url: A SQLAlchemy engine URL.
Works similar to the :ref:`create_database` method in that both url text
and a constructed url are accepted. ::
drop_database('postgres://postgres@localhost/name')
drop_database(engine.url)
"""
url = copy(make_url(url))
database = url.database
if url.drivername.startswith('postgresql'):
url.database = 'template1'
elif not url.drivername.startswith('sqlite'):
url.database = None
engine = sa.create_engine(url)
if engine.dialect.name == 'sqlite' and url.database != ':memory:':
os.remove(url.database)
elif engine.dialect.name == 'postgresql' and engine.driver == 'psycopg2':
from psycopg2.extensions import ISOLATION_LEVEL_AUTOCOMMIT
engine.raw_connection().set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT)
# Disconnect all users from the database we are dropping.
version = list(
map(
int,
engine.execute('SHOW server_version').first()[0].split('.')
)
)
pid_column = (
'pid' if (version[0] >= 9 and version[1] >= 2) else 'procpid'
)
text = '''
SELECT pg_terminate_backend(pg_stat_activity.%(pid_column)s)
FROM pg_stat_activity
WHERE pg_stat_activity.datname = '%(database)s'
AND %(pid_column)s <> pg_backend_pid();
''' % {'pid_column': pid_column, 'database': database}
engine.execute(text)
# Drop the database.
text = 'DROP DATABASE {0}'.format(quote(engine, database))
engine.execute(text)
else:
text = 'DROP DATABASE {0}'.format(quote(engine, database))
engine.execute(text)
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