| From: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
|---|---|
| To: | Parul Lakkad <parul(dot)lakkad(at)gmail(dot)com> |
| Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Disk usage for intermediate results in join |
| Date: | 2014-03-11 12:22:45 |
| Message-ID: | 531F0015.4000200@vmware.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On 03/11/2014 01:24 PM, Parul Lakkad wrote:
> Hi,
>
> I am trying to figure out when disk is used to store intermediate results
> while performing joins in postgres.
>
> According my findings using 'explain analyse ' only merge sort uses disk.
> Can anyone please throw some more light on this?
Hash joins will also spill to disk if the hash-side of the join is large
enough. The planner usually tries to avoid it, but sometimes it happens.
- Heikki
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Alvaro Herrera | 2014-03-11 13:14:18 | Re: [bug fix] pg_ctl always uses the same event source |
| Previous Message | Robert Haas | 2014-03-11 12:13:02 | Re: [ISSUE] pg_dump: schema with OID 0 does not exist |