Core and Enterprise changefeeds offer different levels of configurability. Enterprise changefeeds allow for active changefeed jobs to be paused, resumed, and canceled.
When creating a changefeed, it's important to consider the number of changefeeds versus the number of tables to include in a single changefeed:
- Changefeeds each have their own memory overhead, so every running changefeed will increase total memory usage.
- Creating a single changefeed that will watch hundreds of tables can affect the performance of a changefeed by introducing coupling, where the performance of a watched table affects the performance of the changefeed watching it. For example, any schema change on any of the tables will affect the entire changefeed's performance.
To watch multiple tables, we recommend creating a changefeed with a comma-separated list of tables. However, we do not recommend creating a single changefeed for watching hundreds of tables.
We suggest monitoring the performance of your changefeeds. See Monitor and Debug Changefeeds for more detail.
The following Enterprise and Core sections outline how to create and configure each type of changefeed:
Configure a changefeed
An Enterprise changefeed streams row-level changes in a configurable format to a configurable sink (i.e., Kafka or a cloud storage sink). You can create, pause, resume, and cancel an Enterprise changefeed.
Create
To create an Enterprise changefeed:
> CREATE CHANGEFEED FOR TABLE table_name, table_name2 INTO '{scheme}://{host}:{port}?{query_parameters}';
Parameters should always be URI-encoded before they are included the changefeed's URI, as they often contain special characters. Use Javascript's encodeURIComponent function or Go language's url.QueryEscape function to URI-encode the parameters. Other languages provide similar functions to URI-encode special characters.
For more information, see CREATE CHANGEFEED.
Pause
To pause an Enterprise changefeed:
> PAUSE JOB job_id;
For more information, see PAUSE JOB.
Resume
To resume a paused Enterprise changefeed:
> RESUME JOB job_id;
For more information, see RESUME JOB.
Cancel
To cancel an Enterprise changefeed:
> CANCEL JOB job_id;
For more information, see CANCEL JOB.
Configuring all changefeeds
It is useful to be able to pause all running changefeeds during troubleshooting, testing, or when a decrease in CPU load is needed.
To pause all running changefeeds:
PAUSE JOBS (SELECT * FROM [SHOW CHANGEFEED JOBS] WHERE status = ('running'));
This will change the status for each of the running changefeeds to paused, which can be verified with SHOW CHANGEFEED JOBS.
To resume all running changefeeds:
RESUME JOBS (SELECT * FROM [SHOW CHANGEFEED JOBS] WHERE status = ('paused'));
This will resume the changefeeds and update the status for each of the changefeeds to running.
Create a changefeed
A core changefeed streams row-level changes to the client indefinitely until the underlying connection is closed or the changefeed is canceled.
To create a core changefeed:
> EXPERIMENTAL CHANGEFEED FOR name;
For more information, see EXPERIMENTAL CHANGEFEED FOR.
See also
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