Re: Correlating Asterisk CDRs

On Wednesday 07 Dec 2011, Brent Dombrowski wrote:
> On Dec 7, 2011, at 6:34 AM, Raj Mathur (राज माथुर) wrote:
> > I'm trying to correlate Call Data Records (CDRs) from two Asterisk
> > servers, one of which uses the other for telephony.  The data is in
> > the tables cdr and cdr2.  With some indexes, the query and explain
> > result are:
> >
> > explain analyse select cdr.calldate, cdr2.calldate,
> > (cdr2.calldate-cdr.calldate) as rtdur, cdr.clid, cdr.dst, cdr2.src,
> > cdr2.dst, cdr2.dstchannel, cdr2.lastapp, cdr2.duration,
> > cdr2.disposition from cdr, cdr2 where cdr2.calldate >= cdr.calldate
> > and cdr.clid=cdr2.clid and cdr.dst=substring(cdr2.dst from 4) order
> > by cdr.calldate, cdr2.calldate, cdr.clid limit 100;
> >
> >                                                             QUERY
PLAN
> >
> > -------------------------------------------------------------------
> > -------------------------------------------------------------------
> > ------- Limit  (cost=46782.15..46782.40 rows=100 width=109) (actual
> > time=4077.866..4078.054 rows=100 loops=1)
> >
> >   ->  Sort  (cost=46782.15..46785.33 rows=1272 width=109) (actual
> >   time=4077.863..4077.926
> >
> > rows=100 loops=1)
> >
> >         Sort Key: cdr.calldate, cdr2.calldate, cdr.clid
> >         Sort Method:  top-N heapsort  Memory: 42kB
> >         ->  Merge Join  (cost=2.95..46733.54 rows=1272 width=109)
> >         (actual
> >
> > time=0.070..3799.546 rows=168307 loops=1)
> >
> >               Merge Cond: (((cdr.clid)::text = (cdr2.clid)::text)
> >               AND ((cdr.dst)::text =
> >
> > "substring"((cdr2.dst)::text, 4)))
> >
> >               Join Filter: (cdr2.calldate >= cdr.calldate)
> >               ->  Index Scan using ick1 on cdr
> >               (cost=0.00..34667.86 rows=208798
> >
> > width=43) (actual time=0.022..434.246 rows=208798 loops=1)
> >
> >               ->  Index Scan using i2k1 on cdr2
> >               (cost=0.00..9960.89 rows=65449 width=88)
> >
> > (actual time=0.011..391.599 rows=240981 loops=1)
> > Total runtime: 4078.184 ms
> > (10 rows)
> >
> > Is there any way to make this query faster?  I already have an
> > index i2k1 on substring(cdr2.dst from 4), which is being used.
>
> You have a non-equi join in there (cdr2.calldate >= cdr.calldate). I
> would try to get rid of that. It's increasing the number of rows in
> the result set and will only get worse as your data set grows.

Seen.  At the moment (and in the foreseeable future) the query is going
to be run with a condition of the form "cdr.calldate >=
date_trunc('day', now())", so the set of matches from cdr2 will remain
relatively constant.

However, you're right, the scope of cdr2 calldates also ought to be time
limited.  Have added an "and cdr2.calldate < cdr.calldate + interval '1
day'" to the query.  Thanks.

Regards,

-- Raj
--
Raj Mathur                          || raju@kandalaya.org   || GPG:
http://otheronepercent.blogspot.com || http://kandalaya.org || CC68
It is the mind that moves           || http://schizoid.in   || D17F