Re: Help on indexing timestamps

On Fri, 7 Mar 2003 13:48:04 -0200 (GMT+2)
Achilleus Mantzios <achill@matrix.gatewaynet.com> wrote:

> On Fri, 7 Mar 2003, Andre Schubert wrote:
> 
> > On Fri, 7 Mar 2003 13:01:16 -0200 (GMT+2)
> > Achilleus Mantzios <achill@matrix.gatewaynet.com> wrote:
> > 
> > > On Fri, 7 Mar 2003, Andre Schubert wrote:
> > > 
> > > > Hi all,
> > > > 
> > > > i have a little problem on indexing a table which contains
> > > > about 4 millions of traffic-data.
> > > > My problem is, that a want to select all data from
> > > > a specific month from a specific ip and this select should use the index.
> > > > I use the following select:
> > > 
> > > Did you try to use BETWEEN ??
> > > E.g.
> > > ... and time_stamp between '2003-01-01 00:00:00'::timestamp and 
> > > '2003-02-01 00:00:00'::timestamp
> > > 
> > 
> > Yes and it works if i write the dates by hand, every new month.
> > But the query is executed automatically and i dont want
> > to write in the dates before the query is executed. Maybe the
> > the start and enddate should also be alculated with sql,
> > because i want to create a view from this statement and execute it every month.
> > Or did i miss something.
> 
> You could have an index on the 
> whole 
> date_trunc('month',tbl_traffic.time_stamp),ip
> 
> How does it perform?
> 

I'am not sure how to create such an index...

First: create or replace function trunc_ip(timestamp with time zone) returns timestamptz as       'select
date_trunc(''month'',$1)'language 'sql' with (iscachable);
 
Then: create index idx_test on tbl_traffic using btree( trunc(time_stamp) );

Result: db_km3aue=# explain analyze select sum(inet_up+inet_down) from tbl_traffic where trunc(tbl_traffic.time_stamp)
=trunc('2003-02-01'::timestamptz) and ip = '80.243.40.56';
 
NOTICE:  QUERY PLAN:

Aggregate  (cost=108.78..108.78 rows=1 width=16) (actual time=2278.48..2278.48 rows=1 loops=1) ->  Index Scan using
idx_teston tbl_traffic  (cost=0.00..108.78 rows=1 width=16) (actual time=0.23..2240.50 rows=5346 loops=1)
 
Total runtime: 2278.62 msec

Maybe the problem is, that the index is created without ip as the second column....

[schnipp]