Re: time series data

On Sun, Oct 1, 2017 at 4:17 AM, Khalil Khamlichi <khamlichi(dot)khalil(at)gmail(dot)com
> wrote:

> Hi everyone,
>
> I have a data stream of a call center application coming in to postgres
> in this format :
>
> user_name, user_status, event_time
>
> 'user1', 'ready', '2017-01-01 10:00:00'
> 'user1', 'talking', '2017-01-01 10:02:00'
> 'user1', 'after_call', '2017-01-01 10:07:00'
> 'user1', 'ready', '2017-01-01 10:08:00'
> 'user1', 'talking', '2017-01-01 10:10:00'
> 'user1', 'after_call', '2017-01-01 10:15:00'
> 'user1', 'paused', '2017-01-01 10:20:00'
> ...
> ...
>
> so as you see each new insert of an "event" is in fact the start_time of
> that event and also the end_time of the previous one so should be used to
> calculate the duration of this previous one.
>
> What is the best way to get user_status statistics like total duration,
> frequency, avg ...etc , does any body have an experience with this sort of
> data streams ?
>
>
> Thanks in advance.
>

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.

--
*Melvin Davidson*
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.