> For the complete documentation index, see [llms.txt](https://docs.mediarithmics.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mediarithmics.io/setup-and-monitor/collect-and-manage-your-data/sync-with-your-data-warehouse/data-warehouse-sync.md).

# Data warehouse sync

Declare a warehouse in the Computing Console and pick a synchronisation strategy per table.

## Your goal

Declare your warehouse in the platform and choose, per table, a synchronisation strategy that matches how that table actually changes.

## Expected outcome

A warehouse connection that validates, and synchronisations that bring across the inserts - and the updates and deletes, if that is what you need.

## Declare the warehouse

{% stepper %}
{% step %}

### Prepare the access

Service account, permissions, and credentials file. See [Warehouse compatibilities](/setup-and-monitor/collect-and-manage-your-data/sync-with-your-data-warehouse/warehouse-compatibilities.md).
{% endstep %}

{% step %}

### Open the Data warehouse menu

In the **Computing Console**, under the **Data Store** section, open **Data warehouse**.
{% endstep %}

{% step %}

### Select the provider and fill in the properties

| Property                     | Notes                                                                                                                                                                |
| ---------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Name**                     |                                                                                                                                                                      |
| **Description**              |                                                                                                                                                                      |
| **Location**                 | **BigQuery only.**                                                                                                                                                   |
| **Working dataset / schema** | The [working schema](/setup-and-monitor/collect-and-manage-your-data/sync-with-your-data-warehouse.md#the-decision-that-shapes-everything-else), if you created one. |
| {% endstep %}                |                                                                                                                                                                      |

{% step %}

### Upload the credentials file

Upload or drag and drop it. If the file contains the correct set of permissions, the data warehouse is created. If not, **an error is raised** - which makes this step your permission test.
{% endstep %}
{% endstepper %}

## Choose a strategy per table

The strategy decides which changes in your warehouse reach the datamart. It is a per-table decision, not a global one.

{% hint style="info" %}
This choice concerns tables the platform **reads** to feed the datamart. Where the warehouse is the source of truth for the datamart, the platform also writes into it, and the tables it maintains there are described in [Run your computation in the warehouse](/setup-and-monitor/collect-and-manage-your-data/sync-with-your-data-warehouse/run-your-computation-in-the-warehouse.md).
{% endhint %}

{% tabs %}
{% tab title="Profile data" %}

| Strategy            | What it does                                                                                                                                                      | Needs a working schema |
| ------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------- |
| **Timestamp based** | All updates in the source table - insert, update, delete - are reflected in mediarithmics. Requires a **timestamp column tracking the last update of each line**. | Yes                    |
| **Hash table**      | All updates in the source table - insert, update, delete - are reflected. A temporary table is created based on a hash of columns of the source table.            | Yes                    |
| **Full import**     | Every synchronisation imports the full table. **Append-only** - it does not handle deletes or updates.                                                            | No                     |

Choosing between the two full-fidelity strategies: **timestamp based** if your table already carries a reliable last-update column, **hash table** if it does not.
{% endtab %}

{% tab title="Event data" %}

| Strategy            | What it does                                                                                                                                                                        | Needs a working schema |
| ------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------- |
| **Timestamp based** | Imports all events that occurred since the last import. Requires a **timestamp column tracking when each event occurred**. **Append-only** - it does not handle deletes or updates. | No                     |

Events are naturally append-only, which is why the event strategy does not need a working schema.
{% endtab %}
{% endtabs %}

{% hint style="warning" %}
At the time of synchronisation, if the source table for events contains data that would be affected by active [cleaning rules](/setup-and-monitor/collect-and-manage-your-data/clean-and-delete-data/cleaning-rules.md) on events for the datamart, **those events are not imported**.

This is usually what you want - but it means a backfill of old events will silently import fewer rows than the table contains.
{% endhint %}

## What the strategy costs you

| If you choose                | You accept                                                                                                                    |
| ---------------------------- | ----------------------------------------------------------------------------------------------------------------------------- |
| Full import for profiles     | Deletions and corrections in your warehouse never reach the datamart.                                                         |
| Timestamp based for profiles | A dependency on the timestamp column being maintained correctly - a row updated without touching it is invisible to the sync. |
| Hash table                   | Temporary tables in your working schema, and the write access that implies.                                                   |
| Timestamp based for events   | Nothing unusual, provided event timestamps are accurate.                                                                      |

## Verify

* The warehouse is created without an error, which confirms the permissions.
* A first synchronisation imports the row count you expect - allowing for cleaning rules on events.
* A test update in the warehouse appears in the datamart, if your strategy handles updates.
* A test delete disappears from the datamart, if your strategy handles deletes.
* Collection volumes move for the collections concerned. See [Monitor collection volume](/setup-and-monitor/operate-and-monitor/monitor-collection-volume.md).

## Related pages

<table data-view="cards" data-search="false"><thead><tr><th></th><th></th><th data-hidden data-card-target data-type="content-ref"></th></tr></thead><tbody><tr><td><strong>Warehouse compatibilities</strong></td><td>Permissions and credentials per provider.</td><td><a href="/setup-and-monitor/collect-and-manage-your-data/sync-with-your-data-warehouse/warehouse-compatibilities.md">Warehouse compatibilities</a></td></tr><tr><td><strong>Choose your deployment mode</strong></td><td>Whether the warehouse feeds the datamart or is its source of truth.</td><td><a href="/setup-and-monitor/plan-and-integrate/choose-your-deployment-mode.md">Choose your deployment mode</a></td></tr><tr><td><strong>Cleaning rules</strong></td><td>Why some events are skipped at import.</td><td><a href="/setup-and-monitor/collect-and-manage-your-data/clean-and-delete-data/cleaning-rules.md">Cleaning rules</a></td></tr><tr><td><strong>Data warehouse export</strong></td><td>Sending datamart data back to a warehouse.</td><td><a href="/setup-and-monitor/collect-and-manage-your-data/export-your-data/data-warehouse-export.md">Data warehouse export</a></td></tr></tbody></table>


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