What syntax to use for parsing {{ from_dttm }} and {{ to_dttm }} Jinja variables as datetime objects in Custom SQL queries? - postgresql

Question

Question: How to correctly format {{ from_dttm }} and {{ to_dttm }} default Jinja variables so that they are parsed as datetime objects in Apache Superset Custom SQL metrics?
MWE: Say I want to show what is the time range covered by the data I use in my dashboards — what can be affected by the Time Range filter.
I use the public.birth_names demo dataset for the sake of the example.
So I create a BigNumber chart, with the following custom Metric:
age(
{% if from_dttm is not none %}
'{{ from_dttm }}'
{% else %}
min(ds)
{% endif %}
,
{% if to_dttm is not none %}
'{{ to_dttm }}'
{% else %}
max(ds)
{% endif %}
)
However, if I format the Jinja variables as:
{{ from_dttm }}, I get:
Error: syntax error at or near "{"
LINE 1: SELECT age({{ from_dttm }} , '{{ to_dttm }}') AS "age(
'{{ from_dttm }}', I get
Error: invalid input syntax for type timestamp with time zone: "{{ from_dttm }}"
LINE 1: SELECT age('{{ from_dttm }}'
"{{ from_dttm }}", I get
Error: column "{{ from_dttm }}" does not exist
LINE 1: SELECT age("{{ from_dttm }}" ,
I'm using Superset at 5ae7e5499 (Latest commit on Mar 25, 2022), with PostgreSQL as back-end db engine.

Answer 1

After offline discussion with #villebro, it turns out that:
'{{ from_dttm }}' is the valid syntax — one can try with a simpler example: MIN('{{ from_dttm }}'): this works, whereas both other syntaxes yield an error.
however, there is still a bug in current (version 1.4.*) versions, where {{ from_dttm }} is not rendered (what caused AGE() to yield an error in the particular example above). This issue has been raised in #19564, and a fix submitted in #19565.