0d75776ae5
update the hacking to latest, due to [1] [1]: https://github.com/openstack/oslo.db/blob/master/HACKING.rst Change-Id: I04147f3cbcb9c89a9a1afc1bcb299be8bdf06718
509 lines
18 KiB
Python
509 lines
18 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
|
|
# not use this file except in compliance with the License. You may obtain
|
|
# a copy of the License at
|
|
#
|
|
# http://www.apache.org/licenses/LICENSE-2.0
|
|
#
|
|
# Unless required by applicable law or agreed to in writing, software
|
|
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
|
|
# License for the specific language governing permissions and limitations
|
|
# under the License.
|
|
|
|
import copy
|
|
|
|
from sqlalchemy import inspect
|
|
from sqlalchemy import orm
|
|
from sqlalchemy import sql
|
|
from sqlalchemy import types as sqltypes
|
|
|
|
from oslo_db.sqlalchemy import utils
|
|
|
|
|
|
def update_on_match(
|
|
query,
|
|
specimen,
|
|
surrogate_key,
|
|
values=None,
|
|
attempts=3,
|
|
include_only=None,
|
|
process_query=None,
|
|
handle_failure=None
|
|
):
|
|
"""Emit an UPDATE statement matching the given specimen.
|
|
|
|
E.g.::
|
|
|
|
with enginefacade.writer() as session:
|
|
specimen = MyInstance(
|
|
uuid='ccea54f',
|
|
interface_id='ad33fea',
|
|
vm_state='SOME_VM_STATE',
|
|
)
|
|
|
|
values = {
|
|
'vm_state': 'SOME_NEW_VM_STATE'
|
|
}
|
|
|
|
base_query = model_query(
|
|
context, models.Instance,
|
|
project_only=True, session=session)
|
|
|
|
hostname_query = model_query(
|
|
context, models.Instance, session=session,
|
|
read_deleted='no').
|
|
filter(func.lower(models.Instance.hostname) == 'SOMEHOSTNAME')
|
|
|
|
surrogate_key = ('uuid', )
|
|
|
|
def process_query(query):
|
|
return query.where(~exists(hostname_query))
|
|
|
|
def handle_failure(query):
|
|
try:
|
|
instance = base_query.one()
|
|
except NoResultFound:
|
|
raise exception.InstanceNotFound(instance_id=instance_uuid)
|
|
|
|
if session.query(hostname_query.exists()).scalar():
|
|
raise exception.InstanceExists(
|
|
name=values['hostname'].lower())
|
|
|
|
# try again
|
|
return False
|
|
|
|
persistent_instance = base_query.update_on_match(
|
|
specimen,
|
|
surrogate_key,
|
|
values=values,
|
|
process_query=process_query,
|
|
handle_failure=handle_failure
|
|
)
|
|
|
|
The UPDATE statement is constructed against the given specimen
|
|
using those values which are present to construct a WHERE clause.
|
|
If the specimen contains additional values to be ignored, the
|
|
``include_only`` parameter may be passed which indicates a sequence
|
|
of attributes to use when constructing the WHERE.
|
|
|
|
The UPDATE is performed against an ORM Query, which is created from
|
|
the given ``Session``, or alternatively by passing the ```query``
|
|
parameter referring to an existing query.
|
|
|
|
Before the query is invoked, it is also passed through the callable
|
|
sent as ``process_query``, if present. This hook allows additional
|
|
criteria to be added to the query after it is created but before
|
|
invocation.
|
|
|
|
The function will then invoke the UPDATE statement and check for
|
|
"success" one or more times, up to a maximum of that passed as
|
|
``attempts``.
|
|
|
|
The initial check for "success" from the UPDATE statement is that the
|
|
number of rows returned matches 1. If zero rows are matched, then
|
|
the UPDATE statement is assumed to have "failed", and the failure handling
|
|
phase begins.
|
|
|
|
The failure handling phase involves invoking the given ``handle_failure``
|
|
function, if any. This handler can perform additional queries to attempt
|
|
to figure out why the UPDATE didn't match any rows. The handler,
|
|
upon detection of the exact failure condition, should throw an exception
|
|
to exit; if it doesn't, it has the option of returning True or False,
|
|
where False means the error was not handled, and True means that there
|
|
was not in fact an error, and the function should return successfully.
|
|
|
|
If the failure handler is not present, or returns False after ``attempts``
|
|
number of attempts, then the function overall raises CantUpdateException.
|
|
If the handler returns True, then the function returns with no error.
|
|
|
|
The return value of the function is a persistent version of the given
|
|
specimen; this may be the specimen itself, if no matching object were
|
|
already present in the session; otherwise, the existing object is
|
|
returned, with the state of the specimen merged into it. The returned
|
|
persistent object will have the given values populated into the object.
|
|
|
|
The object is is returned as "persistent", meaning that it is
|
|
associated with the given
|
|
Session and has an identity key (that is, a real primary key
|
|
value).
|
|
|
|
In order to produce this identity key, a strategy must be used to
|
|
determine it as efficiently and safely as possible:
|
|
|
|
1. If the given specimen already contained its primary key attributes
|
|
fully populated, then these attributes were used as criteria in the
|
|
UPDATE, so we have the primary key value; it is populated directly.
|
|
|
|
2. If the target backend supports RETURNING, then when the update() query
|
|
is performed with a RETURNING clause so that the matching primary key
|
|
is returned atomically. This currently includes Postgresql, Oracle
|
|
and others (notably not MySQL or SQLite).
|
|
|
|
3. If the target backend is MySQL, and the given model uses a
|
|
single-column, AUTO_INCREMENT integer primary key value (as is
|
|
the case for Nova), MySQL's recommended approach of making use
|
|
of ``LAST_INSERT_ID(expr)`` is used to atomically acquire the
|
|
matching primary key value within the scope of the UPDATE
|
|
statement, then it fetched immediately following by using
|
|
``SELECT LAST_INSERT_ID()``.
|
|
http://dev.mysql.com/doc/refman/5.0/en/information-\
|
|
functions.html#function_last-insert-id
|
|
|
|
4. Otherwise, for composite keys on MySQL or other backends such
|
|
as SQLite, the row as UPDATED must be re-fetched in order to
|
|
acquire the primary key value. The ``surrogate_key``
|
|
parameter is used for this in order to re-fetch the row; this
|
|
is a column name with a known, unique value where
|
|
the object can be fetched.
|
|
|
|
|
|
"""
|
|
|
|
if values is None:
|
|
values = {}
|
|
|
|
entity = inspect(specimen)
|
|
mapper = entity.mapper
|
|
if [desc['type'] for desc in query.column_descriptions] != \
|
|
[mapper.class_]:
|
|
raise AssertionError("Query does not match given specimen")
|
|
|
|
criteria = manufacture_entity_criteria(
|
|
specimen, include_only=include_only, exclude=[surrogate_key])
|
|
|
|
query = query.filter(criteria)
|
|
|
|
if process_query:
|
|
query = process_query(query)
|
|
|
|
surrogate_key_arg = (
|
|
surrogate_key, entity.attrs[surrogate_key].loaded_value)
|
|
pk_value = None
|
|
|
|
for attempt in range(attempts):
|
|
try:
|
|
pk_value = query.update_returning_pk(values, surrogate_key_arg)
|
|
except MultiRowsMatched:
|
|
raise
|
|
except NoRowsMatched:
|
|
if handle_failure and handle_failure(query):
|
|
break
|
|
else:
|
|
break
|
|
else:
|
|
raise NoRowsMatched("Zero rows matched for %d attempts" % attempts)
|
|
|
|
if pk_value is None:
|
|
pk_value = entity.mapper.primary_key_from_instance(specimen)
|
|
|
|
# NOTE(mdbooth): Can't pass the original specimen object here as it might
|
|
# have lists of multiple potential values rather than actual values.
|
|
values = copy.copy(values)
|
|
values[surrogate_key] = surrogate_key_arg[1]
|
|
persistent_obj = manufacture_persistent_object(
|
|
query.session, specimen.__class__(), values, pk_value)
|
|
|
|
return persistent_obj
|
|
|
|
|
|
def manufacture_persistent_object(
|
|
session, specimen, values=None, primary_key=None):
|
|
"""Make an ORM-mapped object persistent in a Session without SQL.
|
|
|
|
The persistent object is returned.
|
|
|
|
If a matching object is already present in the given session, the specimen
|
|
is merged into it and the persistent object returned. Otherwise, the
|
|
specimen itself is made persistent and is returned.
|
|
|
|
The object must contain a full primary key, or provide it via the values or
|
|
primary_key parameters. The object is peristed to the Session in a "clean"
|
|
state with no pending changes.
|
|
|
|
:param session: A Session object.
|
|
|
|
:param specimen: a mapped object which is typically transient.
|
|
|
|
:param values: a dictionary of values to be applied to the specimen,
|
|
in addition to the state that's already on it. The attributes will be
|
|
set such that no history is created; the object remains clean.
|
|
|
|
:param primary_key: optional tuple-based primary key. This will also
|
|
be applied to the instance if present.
|
|
|
|
|
|
"""
|
|
state = inspect(specimen)
|
|
mapper = state.mapper
|
|
|
|
for k, v in values.items():
|
|
orm.attributes.set_committed_value(specimen, k, v)
|
|
|
|
pk_attrs = [
|
|
mapper.get_property_by_column(col).key
|
|
for col in mapper.primary_key
|
|
]
|
|
|
|
if primary_key is not None:
|
|
for key, value in zip(pk_attrs, primary_key):
|
|
orm.attributes.set_committed_value(
|
|
specimen,
|
|
key,
|
|
value
|
|
)
|
|
|
|
for key in pk_attrs:
|
|
if state.attrs[key].loaded_value is orm.attributes.NO_VALUE:
|
|
raise ValueError("full primary key must be present")
|
|
|
|
orm.make_transient_to_detached(specimen)
|
|
|
|
if state.key not in session.identity_map:
|
|
session.add(specimen)
|
|
return specimen
|
|
else:
|
|
return session.merge(specimen, load=False)
|
|
|
|
|
|
def manufacture_entity_criteria(entity, include_only=None, exclude=None):
|
|
"""Given a mapped instance, produce a WHERE clause.
|
|
|
|
The attributes set upon the instance will be combined to produce
|
|
a SQL expression using the mapped SQL expressions as the base
|
|
of comparison.
|
|
|
|
Values on the instance may be set as tuples in which case the
|
|
criteria will produce an IN clause. None is also acceptable as a
|
|
scalar or tuple entry, which will produce IS NULL that is properly
|
|
joined with an OR against an IN expression if appropriate.
|
|
|
|
:param entity: a mapped entity.
|
|
|
|
:param include_only: optional sequence of keys to limit which
|
|
keys are included.
|
|
|
|
:param exclude: sequence of keys to exclude
|
|
|
|
"""
|
|
|
|
state = inspect(entity)
|
|
exclude = set(exclude) if exclude is not None else set()
|
|
|
|
existing = dict(
|
|
(attr.key, attr.loaded_value)
|
|
for attr in state.attrs
|
|
if attr.loaded_value is not orm.attributes.NO_VALUE and
|
|
attr.key not in exclude
|
|
)
|
|
if include_only:
|
|
existing = dict(
|
|
(k, existing[k])
|
|
for k in set(existing).intersection(include_only)
|
|
)
|
|
|
|
return manufacture_criteria(state.mapper, existing)
|
|
|
|
|
|
def manufacture_criteria(mapped, values):
|
|
"""Given a mapper/class and a namespace of values, produce a WHERE clause.
|
|
|
|
The class should be a mapped class and the entries in the dictionary
|
|
correspond to mapped attribute names on the class.
|
|
|
|
A value may also be a tuple in which case that particular attribute
|
|
will be compared to a tuple using IN. The scalar value or
|
|
tuple can also contain None which translates to an IS NULL, that is
|
|
properly joined with OR against an IN expression if appropriate.
|
|
|
|
:param cls: a mapped class, or actual :class:`.Mapper` object.
|
|
|
|
:param values: dictionary of values.
|
|
|
|
"""
|
|
|
|
mapper = inspect(mapped)
|
|
|
|
# organize keys using mapped attribute ordering, which is deterministic
|
|
value_keys = set(values)
|
|
keys = [k for k in mapper.column_attrs.keys() if k in value_keys]
|
|
return sql.and_(*[
|
|
_sql_crit(mapper.column_attrs[key].expression, values[key])
|
|
for key in keys
|
|
])
|
|
|
|
|
|
def _sql_crit(expression, value):
|
|
"""Produce an equality expression against the given value.
|
|
|
|
This takes into account a value that is actually a collection
|
|
of values, as well as a value of None or collection that contains
|
|
None.
|
|
|
|
"""
|
|
|
|
values = utils.to_list(value, default=(None, ))
|
|
if len(values) == 1:
|
|
if values[0] is None:
|
|
return expression == sql.null()
|
|
else:
|
|
return expression == values[0]
|
|
elif _none_set.intersection(values):
|
|
return sql.or_(
|
|
expression == sql.null(),
|
|
_sql_crit(expression, set(values).difference(_none_set))
|
|
)
|
|
else:
|
|
return expression.in_(values)
|
|
|
|
|
|
def update_returning_pk(query, values, surrogate_key):
|
|
"""Perform an UPDATE, returning the primary key of the matched row.
|
|
|
|
The primary key is returned using a selection of strategies:
|
|
|
|
* if the database supports RETURNING, RETURNING is used to retrieve
|
|
the primary key values inline.
|
|
|
|
* If the database is MySQL and the entity is mapped to a single integer
|
|
primary key column, MySQL's last_insert_id() function is used
|
|
inline within the UPDATE and then upon a second SELECT to get the
|
|
value.
|
|
|
|
* Otherwise, a "refetch" strategy is used, where a given "surrogate"
|
|
key value (typically a UUID column on the entity) is used to run
|
|
a new SELECT against that UUID. This UUID is also placed into
|
|
the UPDATE query to ensure the row matches.
|
|
|
|
:param query: a Query object with existing criterion, against a single
|
|
entity.
|
|
|
|
:param values: a dictionary of values to be updated on the row.
|
|
|
|
:param surrogate_key: a tuple of (attrname, value), referring to a
|
|
UNIQUE attribute that will also match the row. This attribute is used
|
|
to retrieve the row via a SELECT when no optimized strategy exists.
|
|
|
|
:return: the primary key, returned as a tuple.
|
|
Is only returned if rows matched is one. Otherwise, CantUpdateException
|
|
is raised.
|
|
|
|
"""
|
|
|
|
entity = query.column_descriptions[0]['type']
|
|
mapper = inspect(entity).mapper
|
|
session = query.session
|
|
|
|
bind = session.connection(mapper=mapper)
|
|
if bind.dialect.implicit_returning:
|
|
pk_strategy = _pk_strategy_returning
|
|
elif bind.dialect.name == 'mysql' and \
|
|
len(mapper.primary_key) == 1 and \
|
|
isinstance(
|
|
mapper.primary_key[0].type, sqltypes.Integer):
|
|
pk_strategy = _pk_strategy_mysql_last_insert_id
|
|
else:
|
|
pk_strategy = _pk_strategy_refetch
|
|
|
|
return pk_strategy(query, mapper, values, surrogate_key)
|
|
|
|
|
|
def _assert_single_row(rows_updated):
|
|
if rows_updated == 1:
|
|
return rows_updated
|
|
elif rows_updated > 1:
|
|
raise MultiRowsMatched("%d rows matched; expected one" % rows_updated)
|
|
else:
|
|
raise NoRowsMatched("No rows matched the UPDATE")
|
|
|
|
|
|
def _pk_strategy_refetch(query, mapper, values, surrogate_key):
|
|
|
|
surrogate_key_name, surrogate_key_value = surrogate_key
|
|
surrogate_key_col = mapper.attrs[surrogate_key_name].expression
|
|
|
|
rowcount = query.\
|
|
filter(surrogate_key_col == surrogate_key_value).\
|
|
update(values, synchronize_session=False)
|
|
|
|
_assert_single_row(rowcount)
|
|
# SELECT my_table.id AS my_table_id FROM my_table
|
|
# WHERE my_table.y = ? AND my_table.z = ?
|
|
# LIMIT ? OFFSET ?
|
|
fetch_query = query.session.query(
|
|
*mapper.primary_key).filter(
|
|
surrogate_key_col == surrogate_key_value)
|
|
|
|
primary_key = fetch_query.one()
|
|
|
|
return primary_key
|
|
|
|
|
|
def _pk_strategy_returning(query, mapper, values, surrogate_key):
|
|
surrogate_key_name, surrogate_key_value = surrogate_key
|
|
surrogate_key_col = mapper.attrs[surrogate_key_name].expression
|
|
|
|
update_stmt = _update_stmt_from_query(mapper, query, values)
|
|
update_stmt = update_stmt.where(surrogate_key_col == surrogate_key_value)
|
|
update_stmt = update_stmt.returning(*mapper.primary_key)
|
|
|
|
# UPDATE my_table SET x=%(x)s, z=%(z)s WHERE my_table.y = %(y_1)s
|
|
# AND my_table.z = %(z_1)s RETURNING my_table.id
|
|
result = query.session.execute(update_stmt)
|
|
rowcount = result.rowcount
|
|
_assert_single_row(rowcount)
|
|
primary_key = tuple(result.first())
|
|
|
|
return primary_key
|
|
|
|
|
|
def _pk_strategy_mysql_last_insert_id(query, mapper, values, surrogate_key):
|
|
|
|
surrogate_key_name, surrogate_key_value = surrogate_key
|
|
surrogate_key_col = mapper.attrs[surrogate_key_name].expression
|
|
|
|
surrogate_pk_col = mapper.primary_key[0]
|
|
update_stmt = _update_stmt_from_query(mapper, query, values)
|
|
update_stmt = update_stmt.where(surrogate_key_col == surrogate_key_value)
|
|
update_stmt = update_stmt.values(
|
|
{surrogate_pk_col: sql.func.last_insert_id(surrogate_pk_col)})
|
|
|
|
# UPDATE my_table SET id=last_insert_id(my_table.id),
|
|
# x=%s, z=%s WHERE my_table.y = %s AND my_table.z = %s
|
|
result = query.session.execute(update_stmt)
|
|
rowcount = result.rowcount
|
|
_assert_single_row(rowcount)
|
|
# SELECT last_insert_id() AS last_insert_id_1
|
|
primary_key = query.session.scalar(sql.func.last_insert_id()),
|
|
|
|
return primary_key
|
|
|
|
|
|
def _update_stmt_from_query(mapper, query, values):
|
|
upd_values = dict(
|
|
(
|
|
mapper.column_attrs[key], value
|
|
) for key, value in values.items()
|
|
)
|
|
query = query.enable_eagerloads(False)
|
|
context = query._compile_context()
|
|
primary_table = context.statement.froms[0]
|
|
update_stmt = sql.update(primary_table,
|
|
context.whereclause,
|
|
upd_values)
|
|
return update_stmt
|
|
|
|
|
|
_none_set = frozenset([None])
|
|
|
|
|
|
class CantUpdateException(Exception):
|
|
pass
|
|
|
|
|
|
class NoRowsMatched(CantUpdateException):
|
|
pass
|
|
|
|
|
|
class MultiRowsMatched(CantUpdateException):
|
|
pass
|