diff-changelog

The diff-changelog command allows you to receive information on differences between two databases you are comparing and creates a changelog file containing deployable changesets.

The diff-changelog command points out the differences in general and generates changes to resolve most of them.

Uses

The diff-changelog command is typically used when you want to create a deployable changelog to synchronize multiple databases. The diff-changelog command also provides more information about:

  • Missing objects in your database
  • Changes made to your database
  • Unexpected items in your database

Running the diff-changelog command

Running the diff-changelog command requires two URLs:

  • referenceURL – the source for the comparison. The referenceURL attribute represents your source (reference) database which is the starting point and the basis for the database you want to compare.
  • url – the target of the comparison. The URL attribute stands for your target database which you want to compare to the source (reference) database. You typically perform actions and run the commands and against this database.

To create a diff changelog:

  • The first option is to run the diff-changelog command and pass the attributes needed for your source (reference) database and target database.
  • Tip: All commands and parameters use the --kebab-case format in the CLI environment. This is the format Liquibase recommends for best results. If your preference is camelCase, it will still work in the CLI.

    As an example, you can run the following:

    liquibase
    --changelog-file=dbchangelog.xml
    --url="jdbc:oracle:thin:@<IP OR HOSTNAME>:<PORT>:<SERVICE NAME OR SID>"
    --username=<USERNAME>
    --password=<PASSWORD>
    --referenceUrl="jdbc:oracle:thin:@<IP OR HOSTNAME>:<PORT>:<SERVICE NAME OR SID>"
    --referenceUsername=<USERNAME>
    --referencePassword=<PASSWORD>				
    diff-changelog

    Tip: If you want to create an SQL changelog file, add your database type name when specifying the changelog file: liquibase --changelog-file=mychangelog.oracle.sql diff-changelog. Replace .oracle.sql with your database type. When in doubt about your database type name, check Supported Databases.

    See the snapshot command topic for an example of using a snapshot file as one of the databases being used in the command.

    Tip: Liquibase recommends placing the driver .jar file in the LIQUIBASE_HOME/lib directory. If you place the driver file in a different directory, specify the path in the properties file, as follows: classpath:../<path-to-drivers>/ojdbc<version>.jar. For more information, see Specifying Properties in a Connection Profile.
    When running the diff command against two databases, either the drivers for both must reside in the LIQUIBASE_HOME/lib directory or the classpath property must reference both .jar files. Use the appropriate path separator for your operating system, as follows: for Windows, use a semicolon; for Mac or Linux, use a colon.

    Example: classpath: ojdbc7.jar:postgresql-42.2.8.jar

  • Alternatively, configure the Liquibase properties file to include the connection information for both databases. Run the following command:
  • liquibase --changelog-file=file_name.xml diff-changelog

    Note: Replace file_name.xml with your filename and extension format. If you specify a file name that already exists, Liquibase will append your changes to the existing file.

    For information about configuring the Liquibase properties file, see Specifying Properties in a Connection Profile.

Output

The diff-changelog command produces a list of all Objects and creates a changelog with a list of changesets.

Liquibase Community diff-changelog categories:

  • Catalog
  • Column
  • Foreign Key
  • Index
  • Primary Key
  • Schema
  • Sequence
  • Unique Constraints
  • View

Filtering diff-changelog types

You can filter what objects diff-changelog generates with the diffTypes attribute:

--diffTypes=<catalogs,tables,functions,views,columns,indexes,foreignkeys,primarykeys,uniqueconstraints,storedprocedures,triggers,sequences,databasepackage,databasepackagebody>

You can also filter specific objects by name with the includeObjects and excludeObjects attributes. For example:

--includeObjects=table:tableName,column:columnName,view:viewName,index:indexName
--excludeObjects=table:tableName,column:columnName,view:viewName,index:indexName

This way, you can prevent any undesired objects from ending up in the resulting changelog.

Additional Functionality with Liquibase Pro

While Liquibase Community stores all changesets in a changelog, Liquibase Pro creates a directory called Objects and places the directory at the same level as your changelog. The Objects directory contains a subdirectory for each of the following stored logic types:

  • checkconstraint
  • package
  • packagebody
  • procedure
  • function
  • trigger
  • synonyms

Note: Not all database platforms support all stored logic types that are listed.

The diff-changelog command structures stored logic files into timestamped directories every time you run the command.

Note: Liquibase does not currently check data type length.