diff --git a/website/docs/reference/resource-properties/freshness.md b/website/docs/reference/resource-properties/freshness.md index f332f5a1b8f..0b017991d68 100644 --- a/website/docs/reference/resource-properties/freshness.md +++ b/website/docs/reference/resource-properties/freshness.md @@ -37,6 +37,38 @@ A freshness block is used to define the acceptable amount of time between the mo In the `freshness` block, one or both of `warn_after` and `error_after` can be provided. If neither is provided, then dbt will not calculate freshness snapshots for the tables in this source. + + +In most cases, the `loaded_at_field` is required. Some adapters support calculating source freshness from the warehouse metadata tables and can exclude the `loaded_at_field`. + +If a source has a `freshness:` block, dbt will attempt to calculate freshness for that source: +- If a `loaded_at_field` is provided, dbt will calculate freshness via a select query (behavior prior to v1.7). +- If a `loaded_at_field` is _not_ provided, dbt will calculate freshness via warehouse metadata tables when possible (new in v1.7 on supported adapters). + +Currently, calculating freshness from warehouse metadata tables is supported on: +- [Snowflake](/reference/resource-configs/snowflake-configs) + +Support is coming soon to the following adapters: +- [Redshift](/reference/resource-configs/redshift-configs) +- [BigQuery](/reference/resource-configs/bigquery-configs) +- [Spark](/reference/resource-configs/spark-configs) + +Freshness blocks are applied hierarchically: +- a `freshness` and `loaded_at_field` property added to a source will be applied to all all tables defined in that source +- a `freshness` and `loaded_at_field` property added to a source _table_ will override any properties applied to the source. + +This is useful when all of the tables in a source have the same `loaded_at_field`, as is often the case. + +To exclude a source from freshness calculations, you have two options: +- Don't add a `freshness:` block. +- Explicitly set `freshness: null`. + +## loaded_at_field +(Optional on adapters that support pulling freshness from warehouse metadata tables, required otherwise.) + + + + Additionally, the `loaded_at_field` is required to calculate freshness for a table. If a `loaded_at_field` is not provided, then dbt will not calculate freshness for the table. Freshness blocks are applied hierarchically: @@ -47,7 +79,7 @@ This is useful when all of the tables in a source have the same `loaded_at_field ## loaded_at_field (Required) - + A column name (or expression) that returns a timestamp indicating freshness. If using a date field, you may have to cast it to a timestamp: