Re: Help on indexing timestamps

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:
>
> db_nmkm3aue=# explain analyze select sum(inet_up+inet_down) from tbl_traffic where date_trunc('month',tbl_traffic.time_stamp)::timestamptz = date_trunc('month',now() - timespan('1 months')) and ip = '80.243.38.57';
> NOTICE: QUERY PLAN:
>
> Aggregate (cost=116.30..116.30 rows=1 width=16) (actual time=1620.79..1620.79 rows=1 loops=1)
> -> Index Scan using idx_ip_time_stamp on tbl_traffic (cost=0.00..116.30 rows=1 width=16) (actual time=1216.79..1579.89 rows=5232 loops=1)
> Total runtime: 1620.94 msec
>
> But it takes a long time to select the traffic for all Ips.
> Is there a way to select these data with using the index correctly ?
>
> Thanks in advance
>
I have one more solution - try to rewrite your where clause to NOT USE
function on time_stamp. If your query will look like:
select ... where time_stamp between (function with now() returning first
day) and (function with now() returning last day);
your index will work fine.

Regards,
Tomasz Myrta