Date: Wed, 2 Jan 2019 10:45:25 -0600
From: Justin Pryzby <pryzby@telsasoft.com>
To: Abadie Lana <Lana.Abadie@iter.org>
Cc: "pgsql-performance@lists.postgresql.org"
 <pgsql-performance@lists.postgresql.org>
Subject: Re: select query does not pick up the right index
Message-ID: <20190102164525.GU25379@telsasoft.com>
References: <c2d19232595246018b277ebcd59a0046@iter.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <c2d19232595246018b277ebcd59a0046@iter.org>
User-Agent: Mutt/1.5.23 (2014-03-12)
Precedence: bulk

On Wed, Jan 02, 2019 at 04:28:41PM +0000, Abadie Lana wrote:
> css_archive_3_0_0=# explain analyze select t.name, c.smpl_time,c.nanosecs,c.float_val,c.num_                                                                       val,c.str_val,c.datatype,c.array_val from sample c, channel t where t.channel_id=c.channel_i                                                                       d and t.name='BUIL-B36-VA-RT-RT1:CL0001-2-ABW'   order by c.smpl_time desc limit 5;
>  QUERY PLAN
> 
> --------------------------------------------------------------------------------------------
> --------------------------------------------------------------------------------------------
> -------------
> Gather  (cost=1004.71..125606.08 rows=5 width=150) (actual time=38737.443..1220277.244 rows
> =3 loops=1)
>    Workers Planned: 1
>    Workers Launched: 1
>    Single Copy: true

Do you have force_parallel_mode set ?

http://rhaas.blogspot.com/2018/06/using-forceparallelmode-correctly.html

-- 
Justin Pryzby
System Administrator
Telsasoft
+1-952-707-8581