liquibase checks that changesets have not been changed, but doesn't check that they've not been removed: is there a setting to fix this? - liquibase

Question

Liquibase does a pretty good job in keeping the applied changesets consistent with their source-folder.
If you modify a changeset that has already been applied to the db, Liquibase refuses to do anything, even operations that are not related with the modified changeset.
The rule enforced here is: anything that has been applied to the database must be unapplied before changing it (this is a usual workflow during development).
The problem of 'orphaned' changesets
Unfortunately this rule doesn't apply if you just delete the changeset completely.
In this case there will be what I call an 'orphaned' changeset, that is a record on the DATABASECHANGELOG table (and the database object, of course) with liquibase not complaining at all of a missing changeset in the source.
I expected an error at least when you 'bump' into the missing changeset, that is when you try to rollback it, but liquibase simply seems to ignore its presence, it skips it and rolls back the next one. This can be a problem.
The question is: can we change this liquibase behavior via settings? Is this design needed for some use case that I haven't thought of?
I think what I'm asking should be clear enough, however here is an example as demonstration.
Example
<databaseChangeLog ... >
<include relativeToChangelogFile="true" file="CS1.sql"/>
<include relativeToChangelogFile="true" file="CS2.sql"/>
</databaseChangeLog>
My changesets are SQL based files like this:
-- liquibase formatted sql
-- changeset agostinox:-1
CREATE TABLE T1 (
X INT
)
-- rollback DROP TABLE T1
And CS2.sql is the same for the T2 table.
Now i can apply my changesets like this:
PS > liquibase update
...
Liquibase Version: 4.19.0
Liquibase Open Source 4.19.0 by Liquibase
...
Running Changeset: CS1.sql::-1::agostinox
Running Changeset: CS2.sql::-1::agostinox
Liquibase command 'update' was executed successfully.
And on my db, the DATABASECHANGELOG has the following content:
ID
AUTHOR
FILENAME
DATEEXECUTED
ORDEREXECUTED
EXECTYPE
MD5SUM
-1
agostinox
CS1.sql
2023-01-18 18:52:08.476689
1
EXECUTED
8:d966f9ba2b90eaea9b917a6d93962eff
-1
agostinox
CS2.sql
2023-01-18 18:52:08.666667
2
EXECUTED
8:7f2a735fa83b196a0c72885c95362b81
So far so good. Now, now I get to the point.
Let's mess with the CS1.sql, by adding a comment:
-- liquibase formatted sql
-- changeset agostinox:-1
CREATE TABLE T1 (
X INT --Added comment, very harmless but enough to annoy liquibase :-)
)
-- rollback DROP TABLE T1
Now, I try to rollback the last changeset.
PS > liquibase rollbackcount 1
...
Unexpected error running Liquibase: Validation Failed:
1 changesets check sum
CS1.sql::-1::agostinox was: 8:d966f9ba2b90eaea9b917a6d93962eff but is now:
8:2cea5484e81eb542fa94bb67ba2ffdf5
For more information, please use the --log-level flag
You can see that liquibase complains about CS1.sql been changed even if we are not even rolling back CS1.sql but CS2.sql. Actually this change blocks any further operation, so it have to be reverted in order to break the deadlock.
However, if you just remove the changeset, liquibase doesn't complain anymore:
<databaseChangeLog ... >
<!--REMOVED <include relativeToChangelogFile="true" file="CS1.sql"/> -->
<include relativeToChangelogFile="true" file="CS2.sql"/>
</databaseChangeLog>
PS > liquibase rollbackcount 1
...
Rolling Back Changeset: CS2.sql::-1::agostinox
Liquibase command 'rollbackCount' was executed successfully.
But even if liquibase says that everything is successfull, it is not really the case, infact the table DATABASECHANGELOG now contains the 'orphaned' changeset (and the database contains the T1 table since also the rollback code is gone).
ID
AUTHOR
FILENAME
DATEEXECUTED
ORDEREXECUTED
EXECTYPE
MD5SUM
-1
agostinox
CS1.sql
2023-01-18 18:52:08.476689
1
EXECUTED
8:d966f9ba2b90eaea9b917a6d93962eff
For db people, it seems like liquibase does a left join between changesets source folder and records in DATABASECHANGELOG (that is: all the items on the left set are taken and are associated with the matching items on the right set); this way liquibase can see applied migrations and check if their checksum matches. It can also see not-yet-applied migrations (changesets in source folder without a DATABASECHANGELOG record associated) in order to apply them in the next 'update' call.
But it can't see records from DATABASECHANGELOG (the right set) that don't have an associated changeset in the source folder.
This parallel with join operation well explains the liquibase behavior, so let's use it for describing what a better behavior might be.
Liquibase should do a full-join, that is: also the items on the right side that don't have a source changeset associated are considered. Those records indicate an anomaly that is possibly just a 'major version' of the one that you have when a checksum doesn't match. Indeed you can easily think of a null file as a particolar case of checksum, the checksum of null being something necessarily different from the one in the table. Therefore the existence of those non associated record should give the same kind of error. This is what i would expected to truly ensure consistence between source an DATABASECHANGELOG.

Answer 1

I've been curious about this also. I'd recommend opening a github issue so a Liquibase employee can address why they don't do this check. I'm guessing this was done on purpose.
https://github.com/liquibase/liquibase/issues