Created
October 14, 2011 16:19
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sql patcher
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$ python patcher.py | |
-- UPDATE customer to version 1 | |
create table customer ( | |
id integer primary key, | |
); | |
update _schema_version set version='1' where what='customer'; | |
-- UPDATE customer to version 2 | |
alter table customer add column (email text); | |
create unique index foo on customer(email); | |
update _schema_version set version='2' where what='customer'; | |
-- REVERT customer to version 1 | |
alter table customer drop column email; | |
drop index foo; | |
update _schema_version set version='1' where what='customer'; |
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class Patcher: | |
""" | |
I help maintain schema versions | |
""" | |
def __init__(self): | |
self.patches = {} | |
self.reverts = {} | |
def patch(self, what, to_version, sql): | |
""" | |
Record the patch to get to a certain version | |
""" | |
if what not in self.patches: | |
self.patches[what] = {} | |
self.patches[what][to_version] = sql | |
def unpatch(self, what, to_version, sql): | |
""" | |
Record the patch to revert to a certain version | |
""" | |
if what not in self.reverts: | |
self.reverts[what] = {} | |
self.reverts[what][to_version] = sql | |
def update(self, what, from_version, to_version): | |
""" | |
Get the sql needed to update `what` from from_version to to_version | |
""" | |
patches = self.patches[what] | |
for i in xrange(from_version+1, to_version+1): | |
yield '-- UPDATE %s to version %s' % (what, i) | |
for s in patches[i]: | |
yield s + ';' | |
yield "update _schema_version set version='%s' where what='%s';" % (i, what) | |
def revert(self, what, from_version, to_version): | |
""" | |
Get the sql needed to revert `what` from from_version to to_version | |
""" | |
reverts = self.reverts[what] | |
for i in xrange(from_version-1, to_version-1, -1): | |
yield '-- REVERT %s to version %s' % (what, i) | |
for s in reverts[i]: | |
yield s + ';' | |
yield "update _schema_version set version='%s' where what='%s';" % (i, what) | |
sqlite = Patcher() | |
sqlite.patch('customer', 1, [ | |
'''create table customer ( | |
id integer primary key, | |
)''', | |
]) | |
sqlite.unpatch('customer', 0, [ | |
'''drop table customer''', | |
]) | |
sqlite.patch('customer', 2, [ | |
'''alter table customer add column (email text)''', | |
'''create unique index foo on customer(email)''', | |
]) | |
sqlite.unpatch('customer', 1, [ | |
'''alter table customer drop column email''', | |
'''drop index foo''', | |
]) | |
# I want to update customer from nothing to 2 | |
for sql in sqlite.update('customer', 0, 2): | |
print sql | |
print '' | |
# I want to revert customer from 2 to 1 | |
for sql in sqlite.revert('customer', 2, 1): | |
print sql |
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