RedaAffane

SELECT *, 
           CASE WHEN 
               "time_difference" >= INTERVAL '30 days' THEN 1  ELSE 0 END AS "flag_macro_session_limits"
    FROM(
        SELECT *,
               LAG("timestamp",1)  OVER (
                   PARTITION BY "user_id" 
                   ORDER BY "timestamp" DESC
                    )
               - "timestamp" as "time_difference"

RedaAffane

SELECT "user_id", 
       "user_id" || SUM("flag_macro_session_limits") OVER (
            PARTITION BY "user_id" 
            ORDER BY "timestamp" ASC 
           )
           - "flag_macro_session_limits" AS "user_macro_session",
       "channel",
       "timestamp"
FROM(
    SELECT *, 

RedaAffane

def subsets(s):
    '''
    This function returns all the possible subsets of a set of channels.
    input :
            - s: a set of channels.
    '''
    if len(s)==1:
        return s
    else:
        sub_channels=[]