Correcting the issue with miscalculation of the median_vehicle_postion_age.

warehouse/models/mart/gtfs_quality/fct_daily_vehicle_positions_latency_statistics.sql

@@ -0,0 +1,121 @@
+{{ config(
+    materialized='incremental',
+    incremental_strategy='insert_overwrite',
+    partition_by = {
+        'field': 'dt',
+        'data_type': 'date',
+        'granularity': 'day',
+    },
+) }}
+
+WITH vehicle_positions_ages AS (
+    SELECT
+        dt,
+        base64_url,
+        _extract_ts,
+        gtfs_dataset_key,
+        gtfs_dataset_name,
+        _header_message_age,
+        _vehicle_message_age
+    FROM {{ ref('fct_vehicle_positions_messages') }}
+    WHERE {{ incremental_where(default_start_var='PROD_GTFS_RT_START') }}
+),
+
+-- these values are repeated because one row in the source table is one vehicle message so the header is identical for all messages on a given request
+-- select distinct for a given request to deduplicate these to the overall message level to make summary statistics more meaningful
+distinct_headers AS (
+    SELECT DISTINCT
+        dt,
+        base64_url,
+        _extract_ts,
+        _header_message_age,
+    FROM vehicle_positions_ages
+),
+
+header_age_percentiles AS (
+    SELECT
+        *,
+        -- calculate median: https://stackoverflow.com/a/66213692
+        PERCENTILE_CONT(_header_message_age, .5) OVER(PARTITION BY dt, base64_url) AS median_header_message_age,
+        PERCENTILE_CONT(_header_message_age, .25) OVER(PARTITION BY dt, base64_url) AS p25_header_message_age,
+        PERCENTILE_CONT(_header_message_age, .75) OVER(PARTITION BY dt, base64_url) AS p75_header_message_age,
+        PERCENTILE_CONT(_header_message_age, .90) OVER(PARTITION BY dt, base64_url) AS p90_header_message_age,
+        PERCENTILE_CONT(_header_message_age, .99) OVER(PARTITION BY dt, base64_url) AS p99_header_message_age
+    FROM distinct_headers
+),
+
+summarize_header_ages AS (
+    SELECT
+        dt,
+        base64_url,
+        median_header_message_age,
+        p25_header_message_age,
+        p75_header_message_age,
+        p90_header_message_age,
+        p99_header_message_age,
+        MAX(_header_message_age) AS max_header_message_age,
+        MIN(_header_message_age) AS min_header_message_age,
+        AVG(_header_message_age) AS avg_header_message_age
+    FROM header_age_percentiles
+    GROUP BY 1, 2, 3, 4, 5, 6, 7
+),
+
+vehicle_age_percentiles AS (
+    SELECT
+        *,
+        -- calculate median: https://stackoverflow.com/a/66213692
+        PERCENTILE_CONT(_vehicle_message_age, .5) OVER(PARTITION BY dt, base64_url) AS median_vehicle_message_age,
+        PERCENTILE_CONT(_vehicle_message_age, .25) OVER(PARTITION BY dt, base64_url) AS p25_vehicle_message_age,
+        PERCENTILE_CONT(_vehicle_message_age, .75) OVER(PARTITION BY dt, base64_url) AS p75_vehicle_message_age,
+        PERCENTILE_CONT(_vehicle_message_age, .90) OVER(PARTITION BY dt, base64_url) AS p90_vehicle_message_age,
+        PERCENTILE_CONT(_vehicle_message_age, .99) OVER(PARTITION BY dt, base64_url) AS p99_vehicle_message_age
+    FROM vehicle_positions_ages
+),
+
+summarize_vehicle_ages AS (
+    SELECT
+        dt,
+        base64_url,
+        gtfs_dataset_key,
+        gtfs_dataset_name,
+        median_vehicle_message_age,
+        p25_vehicle_message_age,
+        p75_vehicle_message_age,
+        p90_vehicle_message_age,
+        p99_vehicle_message_age,
+        MAX(_vehicle_message_age) AS max_vehicle_message_age,
+        MIN(_vehicle_message_age) AS min_vehicle_message_age,
+        AVG(_vehicle_message_age) AS avg_vehicle_message_age
+    FROM vehicle_age_percentiles
+    GROUP BY 1, 2, 3, 4, 5, 6, 7, 8, 9
+),
+
+fct_daily_vehicle_positions_latency_statistics AS (
+    SELECT
+        {{ dbt_utils.generate_surrogate_key(['dt', 'base64_url']) }} AS key,
+        dt,
+        base64_url,
+        gtfs_dataset_key,
+        gtfs_dataset_name,
+        median_header_message_age,
+        p25_header_message_age,
+        p75_header_message_age,
+        p90_header_message_age,
+        p99_header_message_age,
+        max_header_message_age,
+        min_header_message_age,
+        avg_header_message_age,
+        median_vehicle_message_age,
+        p25_vehicle_message_age,
+        p75_vehicle_message_age,
+        p90_vehicle_message_age,
+        p99_vehicle_message_age,
+        max_vehicle_message_age,
+        min_vehicle_message_age,
+        avg_vehicle_message_age
+    FROM summarize_header_ages
+    LEFT JOIN summarize_vehicle_ages
+        USING (dt, base64_url)
+)
+
+SELECT * FROM fct_daily_vehicle_positions_latency_statistics