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schemadiff.py
299 lines | 8.6 KiB | text/x-python | PythonLexer
"""
Schema differencing support.
"""
import logging
import sqlalchemy
from sqlalchemy.types import Float
log = logging.getLogger(__name__)
def getDiffOfModelAgainstDatabase(metadata, engine, excludeTables=None):
"""
Return differences of model against database.
:return: object which will evaluate to :keyword:`True` if there \
are differences else :keyword:`False`.
"""
db_metadata = sqlalchemy.MetaData(engine)
db_metadata.reflect()
# sqlite will include a dynamically generated 'sqlite_sequence' table if
# there are autoincrement sequences in the database; this should not be
# compared.
if engine.dialect.name == 'sqlite':
if 'sqlite_sequence' in db_metadata.tables:
db_metadata.remove(db_metadata.tables['sqlite_sequence'])
return SchemaDiff(metadata, db_metadata,
labelA='model',
labelB='database',
excludeTables=excludeTables)
def getDiffOfModelAgainstModel(metadataA, metadataB, excludeTables=None):
"""
Return differences of model against another model.
:return: object which will evaluate to :keyword:`True` if there \
are differences else :keyword:`False`.
"""
return SchemaDiff(metadataA, metadataB, excludeTables=excludeTables)
class ColDiff(object):
"""
Container for differences in one :class:`~sqlalchemy.schema.Column`
between two :class:`~sqlalchemy.schema.Table` instances, ``A``
and ``B``.
.. attribute:: col_A
The :class:`~sqlalchemy.schema.Column` object for A.
.. attribute:: col_B
The :class:`~sqlalchemy.schema.Column` object for B.
.. attribute:: type_A
The most generic type of the :class:`~sqlalchemy.schema.Column`
object in A.
.. attribute:: type_B
The most generic type of the :class:`~sqlalchemy.schema.Column`
object in A.
"""
diff = False
def __init__(self,col_A,col_B):
self.col_A = col_A
self.col_B = col_B
self.type_A = col_A.type
self.type_B = col_B.type
self.affinity_A = self.type_A._type_affinity
self.affinity_B = self.type_B._type_affinity
if self.affinity_A is not self.affinity_B:
self.diff = True
return
if isinstance(self.type_A,Float) or isinstance(self.type_B,Float):
if not (isinstance(self.type_A,Float) and isinstance(self.type_B,Float)):
self.diff=True
return
for attr in ('precision','scale','length'):
A = getattr(self.type_A,attr,None)
B = getattr(self.type_B,attr,None)
if not (A is None or B is None) and A!=B:
self.diff=True
return
def __nonzero__(self):
return self.diff
__bool__ = __nonzero__
class TableDiff(object):
"""
Container for differences in one :class:`~sqlalchemy.schema.Table`
between two :class:`~sqlalchemy.schema.MetaData` instances, ``A``
and ``B``.
.. attribute:: columns_missing_from_A
A sequence of column names that were found in B but weren't in
A.
.. attribute:: columns_missing_from_B
A sequence of column names that were found in A but weren't in
B.
.. attribute:: columns_different
A dictionary containing information about columns that were
found to be different.
It maps column names to a :class:`ColDiff` objects describing the
differences found.
"""
__slots__ = (
'columns_missing_from_A',
'columns_missing_from_B',
'columns_different',
)
def __nonzero__(self):
return bool(
self.columns_missing_from_A or
self.columns_missing_from_B or
self.columns_different
)
__bool__ = __nonzero__
class SchemaDiff(object):
"""
Compute the difference between two :class:`~sqlalchemy.schema.MetaData`
objects.
The string representation of a :class:`SchemaDiff` will summarise
the changes found between the two
:class:`~sqlalchemy.schema.MetaData` objects.
The length of a :class:`SchemaDiff` will give the number of
changes found, enabling it to be used much like a boolean in
expressions.
:param metadataA:
First :class:`~sqlalchemy.schema.MetaData` to compare.
:param metadataB:
Second :class:`~sqlalchemy.schema.MetaData` to compare.
:param labelA:
The label to use in messages about the first
:class:`~sqlalchemy.schema.MetaData`.
:param labelB:
The label to use in messages about the second
:class:`~sqlalchemy.schema.MetaData`.
:param excludeTables:
A sequence of table names to exclude.
.. attribute:: tables_missing_from_A
A sequence of table names that were found in B but weren't in
A.
.. attribute:: tables_missing_from_B
A sequence of table names that were found in A but weren't in
B.
.. attribute:: tables_different
A dictionary containing information about tables that were found
to be different.
It maps table names to a :class:`TableDiff` objects describing the
differences found.
"""
def __init__(self,
metadataA, metadataB,
labelA='metadataA',
labelB='metadataB',
excludeTables=None):
self.metadataA, self.metadataB = metadataA, metadataB
self.labelA, self.labelB = labelA, labelB
self.label_width = max(len(labelA),len(labelB))
excludeTables = set(excludeTables or [])
A_table_names = set(metadataA.tables.keys())
B_table_names = set(metadataB.tables.keys())
self.tables_missing_from_A = sorted(
B_table_names - A_table_names - excludeTables
)
self.tables_missing_from_B = sorted(
A_table_names - B_table_names - excludeTables
)
self.tables_different = {}
for table_name in A_table_names.intersection(B_table_names):
td = TableDiff()
A_table = metadataA.tables[table_name]
B_table = metadataB.tables[table_name]
A_column_names = set(A_table.columns.keys())
B_column_names = set(B_table.columns.keys())
td.columns_missing_from_A = sorted(
B_column_names - A_column_names
)
td.columns_missing_from_B = sorted(
A_column_names - B_column_names
)
td.columns_different = {}
for col_name in A_column_names.intersection(B_column_names):
cd = ColDiff(
A_table.columns.get(col_name),
B_table.columns.get(col_name)
)
if cd:
td.columns_different[col_name]=cd
# XXX - index and constraint differences should
# be checked for here
if td:
self.tables_different[table_name]=td
def __str__(self):
""" Summarize differences. """
out = []
column_template =' %%%is: %%r' % self.label_width
for names,label in (
(self.tables_missing_from_A,self.labelA),
(self.tables_missing_from_B,self.labelB),
):
if names:
out.append(
' tables missing from %s: %s' % (
label,', '.join(sorted(names))
)
)
for name,td in sorted(self.tables_different.items()):
out.append(
' table with differences: %s' % name
)
for names,label in (
(td.columns_missing_from_A,self.labelA),
(td.columns_missing_from_B,self.labelB),
):
if names:
out.append(
' %s missing these columns: %s' % (
label,', '.join(sorted(names))
)
)
for name,cd in td.columns_different.items():
out.append(' column with differences: %s' % name)
out.append(column_template % (self.labelA,cd.col_A))
out.append(column_template % (self.labelB,cd.col_B))
if out:
out.insert(0, 'Schema diffs:')
return '\n'.join(out)
else:
return 'No schema diffs'
def __len__(self):
"""
Used in bool evaluation, return of 0 means no diffs.
"""
return (
len(self.tables_missing_from_A) +
len(self.tables_missing_from_B) +
len(self.tables_different)
)