Troubleshooting

As you wire up data ingestion in Materialize, you might run into some snags or unexpected scenarios. This guide collects common questions around data ingestion to help you troubleshoot your sources. See also Monitoring data ingestion

If you’re looking for troubleshooting guidance for slow or unresponsive queries, check out the Transform data troubleshooting guide instead.

Why isn’t my source ingesting data?

First, check the status of your source in the Materialize console by navigating to https://console.materialize.com/, clicking the Sources tab in the navigation bar, and clicking the affected source.

Alternatively, you can get this information from the system catalog by querying the mz_source_statuses table:

SELECT * FROM mz_internal.mz_source_statuses
WHERE name = <SOURCE_NAME>;

Has my source ingested its initial snapshot?

While a source is snapshotting, the source (and the associated subsources) cannot serve queries. That is, queries issued to the snapshotting source (and its subsources) will return after the snapshotting completes (unless the user breaks out of the query).

Snapshotting can take anywhere from a few minutes to several hours, depending on the size of your dataset, the upstream database, the number of tables (more tables can be parallelized in Postgres), and the size of your ingestion cluster.

We’ve observed the following approximate snapshot rates from PostgreSQL:

To determine whether your source has completed ingesting the initial snapshot, you can query the mz_source_statistics system catalog table:

SELECT snapshot_committed
FROM mz_internal.mz_source_statistics
WHERE id = <SOURCE_ID>;

You generally want to aggregate the snapshot_committed field across all worker threads, as done in the above query. The snapshot is only considered committed for the source as a whole once all worker threads have committed their components of the snapshot.

Even if your source has not yet committed its initial snapshot, you can still monitor its progress. See Monitoring data ingestion.

How do I speed up the snapshotting process?

Snapshotting can take anywhere from a few minutes to several hours, depending on the size of your dataset, the upstream database, the number of tables (more tables can be parallelized in Postgres), and the size of your ingestion cluster.

We’ve observed the following approximate snapshot rates from PostgreSQL:

To speed up the snapshotting process, you can scale up the size of the cluster used for snapshotting, then scale it back down once the snapshot completes.

ALTER CLUSTER <cluster_name> SET ( SIZE = <new_size> );

Once the initial snapshot has completed, you can resize the cluster for steady state.

For upsert sources, a larger cluster can not only speed up snapshotting, but may also be necessary to support increased memory usage during the process. For more information, see Use a larger cluster for upsert source snapshotting.

See also

• Monitoring data ingestion