How to add new column with default value from existing column in Liquibase
Solution 1
Since no one answered here I'm posting the way I handled it:
<changeSet id="Add MODIFY_USER_ID to ORDERS" author="Noam">
<addColumn tableName="ORDERS">
<column name="MODIFY_USER_ID" type="BIGINT">
<constraints foreignKeyName="ORDERS_MODIFY_FK" referencedTableName="USERS" referencedColumnNames="ID"/>
</column>
</addColumn>
</changeSet>
<changeSet id="update the new MODIFY_USER_ID column to get the CREATOR" author="Noam">
<sql>update ORDERS set MODIFY_USER_ID = CREATOR</sql>
</changeSet>
<changeSet id="Add not nullable constraint on MODIFY_USER_ID column" author="Noam">
<addNotNullConstraint tableName="ORDERS" columnName="MODIFY_USER_ID" columnDataType="BIGINT"/>
</changeSet>
I've done this in three different change-sets as the documentation recommends
Solution 2
You could use the defaultValueComputed
attribute, which takes the name of a procedure or function. You would have to also create a changeset that creates the procedure.
That might look something like this:
<changeSet author="steve" id="createProcedureForDefaultValue">
<createProcedure procedureName="myCoolProc">
CREATE OR REPLACE PROCEDURE myCoolProc IS
BEGIN
-- actual logic here
END;
</createProcedure>
</changeSet>
<changeSet author="steve" id="addDefaultValueColumn">
<addColumn tableName="ORDERS">
<column name="LAST_MODIFIED_BY" type="VARCHAR" defaultValueComputed="myCoolProc">
<constraints nullable="false"/>
</column>
</addColumn>
</changeSet>
Alternatively, you could do this using the <sql>
tag.
Noam
Updated on February 21, 2020Comments
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Noam about 4 years
I'm using Postgres DB and for migration I'm using Liquibase. I have an ORDERS table with the following columns:
ID | DATE | NAME | CREATOR | ...
I need to add a new column which will hold the user who has last modified the order - this column should be not-nullable and should have default value which is the CREATOR. For new orders I can solve the default value part of the business logic, but thing is I already have an existing orders and I need to set the default value when I create the new column. Now, I know I can set a hard-coded default value in Liquibase - but is there a way I could add the default value based on some other column of that table (for each entity).
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Noam about 8 yearsThanks @SteveDonie, but what should be the WHERE clause in the procedure or the SQL?
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SteveDonie about 8 yearsI don't know what your where clause should be - you didn't specify the condition in your question.
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Noam about 8 yearsWhat I want to accomplish here is mainly to create a new column with the default value - the default value (for existing entries in the table) should be the same value from another column. For example, if I already have an entry in the table like this: ID = 333 DATE = ... NAME = name CREATOR = Steve I want the new created column to have the value 'Steve' as a default value - for new created entries - I will handle the value in the business logic
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Noam about 8 yearsEventually I've managed it in the following manner (all in one changeset): 1) Create a new nullable column 2) Use the <sql> tag to update the new column 3) Add non-nullable constraint on the new column
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Raf over 4 yearsNotice that
<addColumn>
combined with adding not-null constraint is bad practice. It will fail if table contains data. See topic: Adding a non-nullable column to existing table fails.