Code Explainer: Incremental fct_trips

Model (Jinja — same file both runs)

{{
  config(
    materialized='incremental',
    incremental_strategy='merge',
    unique_key='trip_id'
  )
}}
select t.trip_id, t.pickup_datetime, …
from {{ ref('stg_trips') }} t
left join {{ ref('stg_zones') }} pz …
On this run the guard is false — Jinja deletes the block before SQL reaches the warehouse.
On this run the guard is true — the where survives into compiled SQL.
{% if is_incremental() %}
    -- only trips newer than what we already have
    where t.pickup_datetime > (
        select max(pickup_datetime) from {{ this }}
    )
{% endif %}

Compiled SQL (what the warehouse runs)

-- is_incremental() was false → no WHERE
select t.trip_id, t.pickup_datetime, …
from hyf.dev_yourname.stg_trips t
left join hyf.dev_yourname.stg_zones pz …
-- (filter block compiled away)