Sessionized segment tracks & pages (BigQuery)

sessionized_segment_data.sql

/*
This query creates a combined view of tracks and pages from segment data.
Sessions are computed by finding the any session start timestamp denoted by an activity gap of 30 minutes.
Session IDs are assigned to each track or page record using a combination of the session index, user ID, and date.
*/
WITH
  with_session_starts AS (
  SELECT
    *,
    COALESCE( (UNIX_MILLIS(timestamp) - UNIX_MILLIS(LAG(timestamp) OVER (PARTITION BY user_id ORDER BY timestamp ASC)))/(1000*60) >= 30,
      TRUE ) AS session_start_event
  FROM ((
      SELECT
        timestamp,
        user_id,
        context_ip,
        context_page_url,
        context_page_path,
        STRUCT(id,
          event) AS tracks_info,
        STRUCT(NULL AS id,
          NULL AS url,
          NULL AS referrer,
          NULL AS url_hash,
          NULL AS title,
          NULL as name,
          NULL as search,
          NULL as path) AS pages_info
      FROM
        <your_segment_schema>.tracks)
    UNION ALL (
      SELECT
        timestamp,
        user_id,
        context_ip,
        context_page_url,
        context_page_path,
        STRUCT(NULL AS id,
          NULL AS event) AS tracks_info,
        STRUCT(id,
          url,
          referrer,
          url_hash,
          title,
          name,
          search,
          path) AS pages_info
      FROM
        <your_segment_schema>.pages)) 
  WHERE NOT user_id is NULL ),
  with_session_index AS (
  SELECT
    *,
    SUM(
    IF
      ( session_start_event,
        1,
        0 ) ) OVER (PARTITION BY user_id ORDER BY timestamp ASC) AS session_index
  FROM
    with_session_starts ),
  with_session_id AS (
  SELECT
    *,
    farm_fingerprint(CONCAT(CAST(session_index AS STRING), "|", CAST(user_id AS STRING), "|", CAST(DATE(timestamp) AS STRING))) AS session_id
  FROM
    with_session_index)
SELECT
  *
FROM
  with_session_id