Trying to understand md5sum in databasechangelog

Hi All,

First post on these forums. I’m trying to understand the checksum calculated by Liquibase. The MD5SUM value in the DATABASECHANGELOG table clearly seems to consist of two parts:


Where the prefix n is a number or possible a hex nibble, : must be a separator and then the actual checksum hash.

I have studied the source for Liquibase and I’ve hit a force field with CommandBuilder which I haven’t been able to break down and fully grock it’s inner mechanics. I might add that I’m not a Java developer which make things a bit challening to say the least.

When I calculate a MD5 checksum based on input in the format below as a single string it computes to something else so apparently it is not the whole truth:


Does anyone have knowledge about how this actually works and can give me any pointers in the right direction? Any idea what that prefix is?



I can’t really tell you how the md5sum is calculated, but the initial digit appears to the “checksum algorithm version” number. See here for more details:

The combination of filepath:id:author is what is required to make a unique changset in the databasechangelog table. The md5sum represents the “checksum” for the actual code in the changeset.

I’m probably not explaining this exactly correct, but maybe some of what I provided will help you.

1 Like

Thanks Daryl!

I believe I might be on a slightly older version of liquibase so that makes sense. Mine says 8.

I’d be surprised if there is an excessive amount of voodoo going on in the actual md5 calculation. I tried a few simple variants of input but nothing turned out right. So, instead of finding out by doing crazy amounts of trial and error tests I started looking at the code.

Further investigation led me to

        if (!md5sumRS.isEmpty()) {
            String md5sum = md5sumRS.get(0).get("MD5SUM").toString();
            if (!md5sum.startsWith(CheckSum.getCurrentVersion() + ":")) {
                executor.comment("DatabaseChangeLog checksums are an incompatible version.  Setting them to null " +
                    "so they will be updated on next database update");
                databaseChecksumsCompatible = false;
                UpdateStatement updateStatement = new UpdateStatement(database.getLiquibaseCatalogName(),
                        database.getLiquibaseSchemaName(), database.getDatabaseChangeLogTableName())
                        .addNewColumnValue("MD5SUM", null);


I’d say that confirms your find Daryl.

Is there a way to find all the methods for the CheckSum object? I figure there could be a method for generating the CurrentVersion as well and that might provide some more insights if I can find where it is being called.

I’m just a Liquibase user and a DBA. I know nothing about java coding. Hopefully someone else will respond to your question.