Liquibase: changeset auto generate ID - liquibase

Question

How to auto generate ID of changeset with liquibase?
I don't want to set the ID of every changeset manually, is there a way to do it automatically?

Answer 1

I dont think that generated ids are a good idea. The reason is that liquibase uses the changeSet id to calculate the checksum (in addition to the author and fileName). So if you ever insert a changeSet between others the checksums of all subsequent changeSets will change and you will get tons of warnings/errors.
Anyway i can think of those solutions if you still want to generate Ids:
create your own ChangeLogParser
If you parse the ChangeLog on your own you are free to generate the ids as you want.
The downside is that you will have to provide a custom Xml Schema for the changeLog. The schema from Liquibase has a constraint on changeSet ids (required). With a new schema you'll probably have to do a significant amount of tweaking on the parser.
Alternatively you may choose another changeLog Format (YAML, JSON, Groovy). Their parsers may be easier to customize as they do not need that schema definition.
Do some preprocessing
You may write a simple xslt (Xml transformation) that generates a changeLog with changeSet ids, from a file that has none.
use timestamps as Ids
This would be my advice. It does not solve the question the way you asked, but it is simple, consistent, provides additional information and is a good practice for other database migration tools as well http://www.jeremyjarrell.com/using-flyway-db-with-distributed-version-control/

Answer 2

I wrote a Python script to generate unique IDs into Liquibase changelogs.
Be careful!
DO generate IDs
when the changelog is in development or ready for release
or when you control the checksums of the target database
DON'T generate IDs
- when the changelog(s) are deployed already
"""
###############################################################################
Purpose: Generate unique subsequent IDs into Liquibase changelogs
###############################################################################
Args:
param1: Full Windows path changelog directory (optional)
OR
--inplace: directly process changelogs (optional)
By default, XML files in the current directory are processed.
Returns:
In case of success, the output path is returned to stdout.
Otherwise, we crash and drag the system into mordor.
If you feel like wasting time you can:
a) port path handling to *nix
b) handle any obscure exceptions
c) add Unicode support (for better entertainment)
Dependencies:
Besides Python 3, in order to preserve XML comments, I had to use lxml
instead of the stock ElementTree parser.
Install lxml:
$ pip install lxml
Proxy clusterfuck? Don't panic! Simply download a .whl package from:
https://pypi.org/project/lxml/#files and install with pip.
Bugs:
Changesets having id="0" are ignored. Usually, these do not occur.
Author:
Tobias Bräutigam
Versions:
0.0.1 - re based, deprecated
0.0.2 - parse XML with lxml, CURRENT
"""
import datetime
import sys
import os
from pathlib import Path, PureWindowsPath
try:
import lxml.etree as ET
except ImportError as error:
print ('''
Error: module lxml is missing.
Please install it:
pip install lxml
''')
exit()
# Process arguments
prefix = '' # hold separator, if needed
outdir = 'out'
try: sys.argv[1]
except: pass
else:
if sys.argv[1] == '--inplace':
outdir = ''
else:
prefix = outdir + '//'
# accept Windows path syntax
inpath = PureWindowsPath(sys.argv[1])
# convert path format
inpath = Path(inpath)
os.chdir(inpath)
try: os.mkdir(outdir)
except: pass
filelist = [ f for f in os.listdir(outdir) ]
for f in filelist: os.remove(os.path.join(outdir, f))
# Parse XML, generate IDs, write file
def parseX(filename,prefix):
cnt = 0
print (filename)
tree = ET.parse(filename)
for node in tree.getiterator():
if int(node.attrib.get('id', 0)):
now = datetime.datetime.now()
node.attrib['id'] = str(int(now.strftime("%H%M%S%f"))+cnt*37)
cnt = cnt + 1
root = tree.getroot()
# NS URL element name is '' for Etree, lxml requires at least one character
ET.register_namespace('x', u'http://www.liquibase.org/xml/ns/dbchangelog')
tree = ET.ElementTree(root)
tree.write(prefix + filename, encoding='utf-8', xml_declaration=True)
print(str(cnt) +' ID(s) generated.')
# Process files
print('\n')
items = 0
for infile in os.listdir('.'):
if (infile.lower().endswith('.xml')) == True:
parseX(infile,prefix)
items=items+1
# Message
print('\n' + str(items) + ' file(s) processed.\n\n')
if items > 0:
print('Output was written to: \n\n')
print(str(os.getcwd()) + '\\' + outdir + '\n')