With dbt how do I use a model cte in a macro call in a jinja expression? - sql

Question

How would I reference a previously defined cte inside of a macro call, inside of a jinja expression block?
with stg_example_table as (
select *
from {{ ref('stg_db__example_table') }}
where {{ ref('stg_db__example_table') }}.example_column = 'foobar'
),
earliest_date as (
THIS
{{ vvvvvvvvvvvvvvvvv
get_earliest_date('month', 'created_at', stg_example_table)
}} ^^^^^^^^^^^^^^^^^
)
select * from earliest_date
I can't seem to reference the cte, stg_example_table, in that location in a way that works. How should it be referenced in a way that will work?
The macro get_earliest_date(), works if I use ref('stg_db__example_table'). But then I'm getting the wrong value since the table isn't reduced as it would be from the cte.
I could create another stg model that has the filters I need and ref() that one, but it'd be nice to just use the cte here.
I have also tried various forms of:
{% set earliest_date = run_query("select min(created_at)::date from stg_db__example_table").columns[0][0] %}
And then referencing the set earliest_date, but I could not get that to work.
For reference, this is the get_earliest_date() macro:
{% macro get_earliest_date(date_component, column_name, relation) %}
{% set query %}
select
date_trunc({{ date_component }}, min({{ column_name }}))::date as earliest
from {{ relation }}
{% endset %}
{% set results = run_query(query) %}
{% if execute %}
{% set result = results.columns[0][0] %}
{% else %}
{% set result = null %}
{% endif %}
{{ return(result) }}
{% endmacro %}
The example code is simplified, but eventually I want to get a date_spine() with:
{{
dbt_utils.date_spine(
datepart = "month",
start_date = get_earliest_date('month', 'created_at', stg_example_table),
end_date = "date_trunc('month', current_date())"
)
}}

Answer 1

dbt doesn't parse your model, so it simply doesn't know what stg_example_table is.
If you're looking to re-use a CTE, it should probably be its own model (a macro would be another choice). You can use the ephemeral materialization and dbt won't persist anything to your warehouse -- it just interpolates the model as a CTE. There are some limitations for how you can ref an ephemeral model, but I think in this case, since you're calling get_earliest_date from a model, it should work fine.
-- in stg_example_table.sql
{{ config(materialized="ephemeral") }}
select *
from {{ ref('stg_db__example_table') }}
where {{ ref('stg_db__example_table') }}.example_column = 'foobar'
-- in your_model.sql
...
{{
dbt_utils.date_spine(
datepart = "month",
start_date = get_earliest_date('month', 'created_at', ref('stg_example_table')),
end_date = "date_trunc('month', current_date())"
)
}}