Warning when precondition references column starting with underscore about liquibase HOT 3 OPEN

Adding schemaName="${database.defaultSchemaName}" to the columnExists precondition gets rid of the exception and warning.

from liquibase.

Hi @PetterIsberg, thank you for reporting this issue.

I have been able to replicate it with Liquibase versions 4.24.0 and the latest 4.27.0. The warning appears only for MySQL and only for the columnExists precondition.

Having a column starting with an underscore will not generate any warnings. Referencing that column with columnExists will.

If this is done with a table starting with an underscore, the tableExists precondition does't generate any warnings either.

It's a strange bug for sure, but luckily it doesn't block the execution of the changesets. I'll be leaving this ticket open for the community to propose a fix for. Our development team will be available to provide guidance if necessary.

Thank you,
Tatiana

from liquibase.

The reason Liquibase acts differently based on the column name starting with a _ is this line of code in ColumnExistsPrecondition. Because of the underscore, the existence of the column is checked using a snapshot instead of a single SQL query.

Changing the regexp to match columns with a starting underscore works with MySQL, but I'm not sure it will work for every database. I think there is probably a safer fix.

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