In Liquibase, how can I rollback changes made to "rerunnable" (runOnChange=true) changesets? - liquibase

Question

In my liquibase project, I have an sql view that is defined within a file called create_myview.sql.
Each time a change is made to the view, i.e. a column is dropped or renamed, instead of creating a new changeset that contains an ALTER statement, the view definition itself in this file is changed.
This file has the runOnChange attribute set to true so that when changes are made, the view is dropped and recreated the next time liquibase update is run. As such the same file can be run over and over when its contents change, i.e. it is "rerunnable".
Since previous definitions of the view are overwritten with each change, rolling back to a previous version presents a challenge and I am unable to work out the best way to do this.
Currently the only way that I am storing the previous view definitions is through git branches, i.e. with each view change I create a new branch.
Ideally I would like to checkout an old branch and be able to rollback to the definition that is currently checked out. I would like to be able to hop between versions easily.
Other non-rerunnable changesets defined in my project use a --rollback tag that is specified in the sql file and provides the inverse sql operation to each table change i.e. if a column is added to a table using an alter statement, then the inverse sql statement specified looks like:
-- rollback ALTER TABLE x DROP COLUMN name;
The equivalent of using this tag in my rerunnable view file would be to copy the entire previous view definition into this rollback tag, which doesn't seem like it would be best practice.
However, liquibase rollback doesn't seem to work without the --rollback tag being specified.
The file structure:
myDB/
changelog/
ver1/
rerunnable/
create_myview.sql
rerunnable.myDB.xml
myDB.changelog-root.xml
This is how I would make changes and update my view from one version to the next.
checkout new branch
git checkout -b c-01
add changes to view
create_myview.sql:
-- changeset john:c-01 runOnChange:true
DROP VIEW my_view IF EXISTS my_view;
CREATE my_view AS
SELECT name, date
FROM my_table;
...
update the changeset attributes
rerunnable.myDB.xml
<changeSet author="john" id="c-01">
<tagDatabase tag="1.0.0"/>
</changeSet>
Run liquibase update.
Next, an update is made to the view when the date column is dropped.
git checkout -b c-02
-- changeset john:c-02 runOnChange:true
DROP VIEW my_view IF EXISTS my_view;
CREATE my_view AS
SELECT name
FROM my_table;
...
<changeSet author="john" id="c-02">
<tagDatabase tag="2.0.0"/>
</changeSet>
liquibase update
At this point, the view in the database is up to date with the latest update, without the date column, and the databasechangelog looks like:
id
author
orderexecuted
md5sum
description
tag
c-01
john
1
83h8hs...
tagDatabase
1.0.0
c-01
john
2
ln9n2b1...
sql
c-02
john
3
ib309bd...
tagDatabase
2.0.0
c-02
john
4
lmxo21...
sql
From this point I am unable to rollback to how the view was at c-01/1.0.0.
The behaviour that I expect/hope is possible would be something like:
check out branch c-01
the old view definition is now in the working directory
run liquibase rollback or liquibase update
the view in the database is dropped and recreated with the c-01 schema (with the date column).
The changelog only has the first 2 lines.
Unfortunately, liquibase update does nothing, and liquibase rollback specifies that I need a --rollback statement.
would the runAlways attribute work here as a good solution?

Answer 1

For those not on the Liquibase forums, I answered this question there:
https://forum.liquibase.org/t/how-do-i-manage-rolling-back-changes-made-to-rerunnable-runonchange-true-changelogs-that-contain-stored-logic/7780