Modify source or table schemas
This topic describes how to modify the schema of a RisingWave source or table.
When the schema of your upstream source changes (i.e. adding or removing columns), you need to modify the schema of the corresponding source or table in RisingWave to ensure they are aligned.
If the schema registry is used to create a source or table, you cannot modify the schema of the source or table.
Add a column
To add a column to a source, use this command:
Similarly, to add a column to a table, use this command:
For details about these two commands, see ALTER SOURCE and ALTER TABLE.
Note that you cannot add a primary key column to a source or table in RisingWave. To modify the primary key of a source or table, you need to recreate the table.
When you add a column to a source or table, the new column is not automatically picked up in a downstream materialized view.
For example, if you have a materialized view mv1
that is created with this statement:
When you add a column to my_kafka_source
:
The materialized view mv1
does not contain the new column new_col
. If you want to pick up this new column, you’ll need to create a new materialized view.
Remove a column
You cannot remove a column from a source in RisingWave. If you intend to remove a column from a source, you’ll need to drop the source and create the source again.
If a column of a table is referenced in a materialized view, you cannot remove the column. This is to ensure data consistency and prevent disruptions to downstream data processing.
To remove a column from a table, use this command:
Refresh the schema registry
Source
At present, combined with the ALTER SOURCE command, you can refresh the schema registry of a source by refilling its FORMAT and ENCODE options. The syntax is:
Here is a simple example. Let’s assume we have a source as follows:
Then you can refresh the schema registry by the following command:
Currently, it is not supported to modify the data_format
and data_encode
. Furthermore, when refreshing the schema registry of a source, it is not allowed to drop columns or change types.
In addition, when the FORMAT and ENCODE options are not changed, the REFRESH SCHEMA
clause of ALTER SOURCE
can also be used to refresh the schema of a source.
For example, assume we have a source as follows:
Create a source
Then we can refresh its schema with the following statement:
Refresh schema
For more details about this example, see our test file.
Table
Similarly, you can use the following statement to refresh the schema of a table with connectors. For more details, see ALTER TABLE.
Refresh schema of table
If a downstream fragment references a column that is either missing or has undergone a type change in the updated schema, the command will be declined.
See also
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