Question

First, I am sorry as I could not come up with better title for this question.

I have a badge/achievement system in my website, community users are rewarded specific badges according to their activity in the website, below sql example I use to pull the number of users who made at at least 100 forum posts (I am using informix db version 10)

SELECT tjm.userid::INTEGER AS user_id, 
  EXTEND(DBINFO("UTC_TO_DATETIME",tjm.creationdate/1000), year to fraction) 
    AS earned_date
FROM TABLE(
  MULTISET(
    SELECT jm.userid, jm.creationdate, (
      SELECT COUNT(*) from TABLE(
        MULTISET(
          SELECT userid, creationdate
          FROM jive:jivemessage
        )
      ) AS i 
      WHERE i.userid = jm.userid AND i.creationdate < jm.creationdate
    ) + 1 AS row_num
    FROM jive:jivemessage jm 
  )
) AS tjm 
WHERE tjm.row_num=100

This sql takes around more than 30 minutes to execute, we have a very large community and there are millions of forum posts.

I would like to know if there is a solution to improve the query performance? I am trying to reduce the execution time because I have 40 sql queries similar to this one but for different tables and activities.

Answer 1

I don’t now Informix DB, but the query below should do what you ask and it’s ANSI SQL (except for the EXTEND part, which I copied from your original query).

SELECT
  jm.userid
  ,EXTEND(DBINFO("UTC_TO_DATETIME",tjm.creationdate/1000), year to fraction) AS earned_date
FROM
  (
  -- This sub-query will return all Users who have 100 messages or more
  SELECT
    jm.userid
    ,count(jm.userid) as totalmessages
  FROM
    jive:jivemessage jm
  GROUP BY
    jm.userid
  HAVING
    count(jm.userid) >= 100) AS MessageCount

The above could probably be done without having to use a sub-query. The only reason why I used it is to have the DateEarned, as per original query, in the result set. Adding it to the sub-query would have required adding it to the GROUP BY, with unpredictable results if the query runs across two days (e.g. at 23:59:59).

Update 2012/08/14 – Rewritten query following new requirements

As I stated before, I don’t know Informix at all, therefore the following query may or may not run.

SELECT
  UsersWithBadge.userid
  ,MAX(UsersWithBadge.creationdate) as dateearned
FROM
  (
  SELECT FIRST 100
    jm.userid
    ,jm.creationdate
  FROM
    jive:jivemessage jm
    JOIN
    (-- This sub-query will return all Users who have 100 messages or more
    SELECT
      jm.userid
      ,count(jm.userid) as totalmessages
    FROM
      jive:jivemessage jm
    GROUP BY
      jm.userid
    HAVING
      count(jm.userid) >= 100)
    AS MessageCount ON
      (MessageCount.userid = jm.userid)
  ) AS UsersWithBadge     
GROUP BY
  UsersWithBadge.userid