Warehouse Syncs

Instead of constantly streaming data to the warehouse destination, Segment loads data to the warehouse in bulk at regular intervals. Before the data loads, Segment inserts and updates events and objects, and automatically adjusts the schema to make sure the data in the warehouse is inline with the data in Segment.

When Segment loads data into your warehouse, each sync goes through two steps:

  1. Ping: Segment servers connect to your warehouse. For Redshift warehouses, Segment also runs a query to determine how many slices a cluster has. Common reasons a sync might fail at this step include a blocked VPN or IP, a warehouse that isn’t set to be publicly accessible, or an issue with user permissions or credentials.
  2. Load: Segment de-duplicates the transformed data and loads it into your warehouse. If you have queries set up in your warehouse, they run after the data is loaded into your warehouse.

Warehouses sync with all data coming from your source. However, Business plan members can manage the data that is sent to their warehouses using Selective Sync.

Sync Frequency

Your plan determines how frequently data is synced to your warehouse.

Plan Frequency
Free Once a day (every 86,400 seconds)
Team Twice a day (every 43,200 seconds)
Business* Up to 24 times a day. Generally, these syncs are fixed to the top of the hour (:00), but these times can vary.

*If you’re a Business plan member and would like to adjust your sync frequency, you can do so using the Selective Sync feature. To enable Selective Sync, please go to Warehouse > Settings > Sync Schedule.

Why can't I sync more than 24 times per day?

We do not set syncs to happen more than once per hour (24 times per day). The warehouse product is not designed for real-time data, so more frequent syncs would not necessarily be helpful.

Sync History

You can use the Sync History page to see the status and history of data updates in your warehouse. The Sync History page is available for every source connected to each warehouse. This page helps you answer questions like, “Has the data from a specific source been updated recently?” “Did a sync completely fail, or only partially fail?” and “Why wasn’t this sync successful?”

The Sync History includes the following information:

  • Sync Status: The possible statuses are:
    • Success: The sync run completed without any notices and all rows synced, OR no rows synced because no data was found.
    • Partial: The sync run completed with some notices and some rows synced.
    • Failure: The sync run completed with some notices and no rows synced.
  • Start Time: The time at which the sync began. This is shown in your local timezone.
  • Duration: The length of time the sync took.
  • Synced Rows: Number of rows successfully synced from the sync run.
  • Notices: A list of errors or warnings found, which could indicate problems with the sync run. Click a notice message to show details about the result, and any errors or warnings for each collection included in the sync run.

If a sync run shows a partial success or failure, the next sync attempts to sync any data that was not successfully synced in the prior run.

View the Sync History

To view the Sync History:

  1. Go to Connections > Destinations and choose the warehouse destination you want to view the sync history for.
  2. Click the source you want to view the sync history for.
  3. (Optional) Click on any of the rows in the Sync History table to see additional details related to that sync. You can view:
    • The Results of your sync which shows the number of rows synced for each collection.
    • The Sync Duration which shows the Preparation and Loading times of your sync.

Warehouse Selective Sync

Warehouse Selective Sync allows you to manage the data that you send to your warehouses. You can use this feature to stop syncing specific events (also known as collections) or properties that aren’t relevant, and may slow down your warehouse syncs.

This feature is only available to Business Tier customers.

You must be a Workspace Owner to change Selective Sync settings.

With Selective Sync, you can customize which collections and properties from a source are sent to each warehouse. This helps you control the data that is sent to each warehouse, allowing you to sync different sets of data from the same source to different warehouses.

NOTE: This feature only affects warehouses, and doesn’t prevent data from going to any other destinations.

When you disable a source, collection or property, Segment no longer syncs data from that source. Segment won’t delete any historical data from your warehouse. When you re-enable a source, Segment syncs all events since the last sync. This doesn’t apply when a collection or property is re-enabled. Only new data generated after re-enabling a collection or property will sync to your warehouse.

For each warehouse only the first 5,000 collections per source and 5,000 properties per collection are visible in the Selective Sync user interface. Learn more about the limits.

Disabling the received_at column will cause your syncs to fail, as all tables use received_at as the sort key.

When to use Selective Sync

By default, all sources and their collections and properties are sent, and no data is prevented from reaching warehouses.

When you disable sources, collections, or properties using Selective Sync, Segment stops sending new data for these sources, collections, or properties to your warehouse. It doesn’t delete any existing data in the warehouse.

If you choose to re-enable a source to begin syncing again, Segment loads all data that arrived since the last sync into the warehouse, but doesn’t backfill data that was omitted while these were disabled. When a collection or property is re-enabled, data only syncs going forward. It will not be loaded from the last sync.

Enable Selective Sync

To use Selective Sync:

  1. Go to Connections > Destinations and select the warehouse you want to enable Selective Sync for.
  2. Click the Settings tab and click Selective Sync in the left menu.
  3. Select which sources, collections, and properties to sync. All that is not selected won’t be synced to your warehouse.
  4. Click Save Changes.

Change sync settings to a single warehouse from multiple sources

To change the sync settings to a single warehouse from multiple sources, follow the same steps as above.

This may be valuable if you’re looking to make changes in bulk, such as when setting up a new warehouse.

Change sync settings on a specific Warehouse to Source connection

To manage data from one specific source to an individual warehouse:

  1. Go to Connections > Destinations and select the warehouse you want to change the sync settings for.
  2. On the Warehouse Overview page, click the Schema you want to change the sync settings for.
  3. On the Settings tab of the Sync History page for that source, select the data you want synced to your warehouse, or deselect the data you don’t want synced.

This may be valuable when you’re making smaller changes, for example, disabling all properties from one unnecessary collection.

All changes made through Selective Sync only impact an individual warehouse. They don’t impact multiple warehouses at once. To make changes to multiple warehouses, you need to enable/disable data for each individual warehouse.

Selective Sync User Interface Limits

Regardless of schema size, for each warehouse only the first 5,000 collections per source and 5,000 properties per collection can be managed using the Selective Sync user interface. After you hit any of these limits, all future data is still tracked and sent to your warehouse. New collections created after hitting this limit is not displayed in the Selective Sync table.

You will see a warning in the Selective Sync user interface when the warehouse schema has reached 80% of the limit for collections and/or properties. An error message will appear when you’ve reached the limit.

Contact Support to edit Selective Sync settings for any collections and/or properties which exceed the limit.

Only Workspace Owners can change Selective Sync settings.

This page was last modified: 20 Mar 2024

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