Re: [GENERAL] time series data - Mailing list pgsql-general

Just a suggestion, but here is what I would do.
First, create your tables similar to as follows

CREATE TABLE status
(
 call_status    varchar(10) NOT NULL,
 CONSTRAINT status_pk PRIMARY KEY (call_status)
);

INSERT INTO status
(call_status)
VALUES
('ready'),
('talking'),
('after_call');

CREATE TABLE user_sessions
(
 username        name        NOT NULL,
 session_id        bigint        NOT NULL,
 call_status    varchar(10) NOT NULL,
 call_time        timestamp NOT NULL,
 CONSTRAINT user_sessions_pk PRIMARY KEY (username, session_id,call_status),
 CONSTRAINT user_sessions_fk_status FOREIGN KEY (call_status)
    REFERENCES status(call_status)
);

Next, you will need to generate a unique session_id for each
user, but only for when call_status is 'ready'. So probably
a table of the form:

CREATE TABLE current_session
(
username        name        NOT NULL,
session_id        serial        NOT NULL,
CONSTRAINT current_session_pk PRIMARY KEY (username)
);

Then all you need to do is:
1. Update current_session and get the new session_id each time a user connects (call_status = 'ready'.
   Probably best to use a BEFORE trigger to do this, but you will need to code it yourself.

2. You can then do

SELECT username,
       age ( (SELECT call_time FROM current_session WHERE call_status = 'talking'),
              ( SELECT call_time FROM current_session WHERE call_status = 'after_call')
           ) as duration
  FROM user_sessions
 WHERE username = 'actual_user_name'
   AND session_id =  actual_session_id;  

You can use similar queries for avg and frequency.

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