skipping liquibase change if table exists

问题

New to liquibase. I have an existing schema managed by hibernate. I now need to remove some tables and I'm using liquibase. I wrote a config that succesfully deletes the table.

But I want the check to run only if the table exists, since a new install of the system would not have the table since the hibernate mapping objects no longer exist.

I attempted to add a precondition. However, my logs still indicating that liquibase is failling becuase it tries to delete the table and it doesn't exist. What am I not doing correctly? I'm using Spring Boot / Java

databaseChangeLog:
  - preConditions:
      on-fail: mark_ran
      on-error: mark_ran
      tableExists:
        tableName: some_old_table
        schemaName: public
  - changeSet:
      id: 01_del_old_table
      author: some-dev-01
      comment: Remove old table
      changes:
        - dropTable:
            tableName: some_old_table

error in log: Table public.some_old_table does not exist ...

PreconditionFailedException

It's like ti's checking the preconditions... and still failing them.

Also tried

databaseChangeLog:
  - changeSet:
      id: zzchange-1.0-remove-xczczxc
      author: zzzz
      comment: Remove some_old_table table - no longer needed
      preConditions:
        on-fail: mark_ran
        tableExists:
          tableName: some_old_table
      changes:
        - dropTable:
            tableName: some_old_table

回答1:

In your second try put your comment after your precondition

databaseChangeLog:
  - changeSet:
      id: zzchange-1.0-remove-xczczxc
      author: zzzz
      preConditions:
        on-fail: mark_ran
        tableExists:
          tableName: some_old_table
      comment: Remove some_old_table table - no longer needed
      changes:
        - dropTable:
            tableName: some_old_table

This is what they recommend in liquibase documentation here: https://www.liquibase.org/documentation/preconditions.html

I am not really sure why your first try will not work but however I don't think it is a good idea to have a global precondition. This is because what they say in the same documentation:

Preconditions at the changelog level apply to all changesets, not just those listed in the current changelog or its child changelogs.

回答2:

The issue was in the on-fail attribute not being spelled correctly. on-fail should be onFail.

As @Julian mentioned, it's best to put a precondition scoped to a specific change set, and the comment should go after a preCondition, although that was not the issue at hand here.

databaseChangeLog:
  - changeSet:
      id: zzchange-1.0-remove-xczczxc
      author: zzzz
      preConditions:
        on-fail: mark_ran
        tableExists:
          tableName: some_old_table
      comment: Remove some_old_table table - no longer needed
      changes:
        - dropTable:
            tableName: some_old_table

来源：https://stackoverflow.com/questions/57562687/skipping-liquibase-change-if-table-exists

标签

java

database

hibernate

liquibase