Can I add Index to make a query faster which involves joins on unnest ?

2018-09-13 Thread Arup Rakshit
The below query basically gives the result by maintaining the order of the sizes in the list. explain analyze select "price_levels"."name", "price_levels"."size" from "price_levels" join unnest(array['M', 'L', 'XL', '2XL', '3XL', '4X

Re: Can I add Index to make a query faster which involves joins on unnest ?

2018-09-13 Thread Rob Sargent
> On Sep 13, 2018, at 12:17 PM, Arup Rakshit wrote: > > The below query basically gives the result by maintaining the order of the > sizes in the list. > > explain analyze select > "price_levels"."name", > "price_levels"."size" > from > "price_levels" > join unnest(arr

Estimate time without running the query

2018-09-13 Thread Neto pr
Dear all, Only a doubt. The Explain command only estimates the cost of execution of a query, and does not estimate time for execution. I would like know if exists some way to estimate the time, without running the query? Best Regards []`s Neto

RE: Estimate time without running the query

2018-09-13 Thread Johnes Castro
Hi netoprbr, Use a command explain analyse. Best Regards. Johnes Castro De: Neto pr Enviado: quinta-feira, 13 de setembro de 2018 19:38 Para: PostgreSQL General Assunto: Estimate time without running the query Dear all, Only a doubt. The Explain command only es

Re: [External] RE: Estimate time without running the query

2018-09-13 Thread Vijaykumar Jain
explain analyze would *run* the query and it can be dangerous if it is a DML statement like insert/update/delete 😊 If you still want to go with explain analyze, You can do begin; explain analyze ; rollback; thanks, Vijay From: Johnes Castro Date: Friday, September 14, 2018 at 3:12 AM To: Neto

Slow shutdowns sometimes on RDS Postgres

2018-09-13 Thread Chris Williams
Hi, I'm using AWS RDS Postgres (9.6.6) and have run into very slow shutdowns (10+ minutes) a few times when making database modifications (e.g. reboot, changing instance size, etc.). Other times, it shuts down quickly (1 minute or so). I have not been able to figure out why sometimes it takes a

Re: Slow shutdowns sometimes on RDS Postgres

2018-09-13 Thread Joshua D. Drake
On 09/13/2018 03:04 PM, Chris Williams wrote: Hi, I'm using AWS RDS Postgres (9.6.6) and have run into very slow shutdowns (10+ minutes) a few times when making database modifications (e.g. reboot, changing instance size, etc.).  Other times, it shuts down quickly (1 minute or so).  I have no

Re: [External] RE: Estimate time without running the query

2018-09-13 Thread Neto pr
Em qui, 13 de set de 2018 às 18:49, Vijaykumar Jain escreveu: > explain analyze would *run* the query and it can be dangerous if it is a > DML statement like insert/update/delete 😊 > > > > If you still want to go with explain analyze, > > You can do > > > > begin; > > explain analyze ; > > rollba

Behaviour when autovacuum is canceled

2018-09-13 Thread Martín Fernández
Hello, I'm working on a high volume transaction database and we are starting to tune our autovacuum setting to improve our vacuuming performance. Once thing that we know about autovacuum is that is can be automatically canceled if a dependent transaction is blocked by the autovacuum transaction

Re: [External] RE: Estimate time without running the query

2018-09-13 Thread David G. Johnston
On Thu, Sep 13, 2018 at 3:30 PM, Neto pr wrote: > The problem is that using the explain analyze I have to wait for > the query to execute. > I would like to estimate the time without having to wait for the query > execution. > Does anyone know how to estimate the time without waiting for the que

Re: Behaviour when autovacuum is canceled

2018-09-13 Thread David G. Johnston
On Thu, Sep 13, 2018 at 3:45 PM, Martín Fernández wrote: > From what I could understand (that can be totally wrong), the vacuum > process is split in multiple small transactions. If the autovacuum is > canceled, could it be possible that only the latest transaction work be > lost > >From the doc

Re: Slow shutdowns sometimes on RDS Postgres

2018-09-13 Thread Chris Williams
Yeah, I figured that. Unfortunately, every time it happens, I open a support ticket with them, but they always just tell me that this is normal behavior for postgres. Whether it's "normal" or not, I really would like to get my db to shut down faster, and their suggestion of manually shutting down

Re: Behaviour when autovacuum is canceled

2018-09-13 Thread Martín Fernández
David, Thanks a lot for the quick reply.  I clearly misunderstood the references in the code.  Best, Martín On Thu, Sep 13th, 2018 at 7:55 PM, "David G. Johnston" wrote: > > > On Thu, Sep 13, 2018 at 3:45 PM, Martín Fernández < fmarti...@gmail.com > > wrote: > > >> From what I could un

Re: Slow shutdowns sometimes on RDS Postgres

2018-09-13 Thread Adrian Klaver
On 9/13/18 3:59 PM, Chris Williams wrote: Yeah, I figured that.  Unfortunately, every time it happens, I open a support ticket with them, but they always just tell me that this is normal behavior for postgres.  Whether it's "normal" or not, I really would like to get my db to shut down faster,

Re: Behaviour when autovacuum is canceled

2018-09-13 Thread Martín Fernández
David, Your last comment applies for cleaning up indexes as well ? We performed a simple test in our production database to understand behaviour and we got a result that surprised us based on your last comment. We basically started a VACUUM on a given table, waited for one index to process (ca

Re: [External] RE: Estimate time without running the query

2018-09-13 Thread Neto pr
Em qui, 13 de set de 2018 às 19:53, David G. Johnston < david.g.johns...@gmail.com> escreveu: > On Thu, Sep 13, 2018 at 3:30 PM, Neto pr wrote: > >> The problem is that using the explain analyze I have to wait for >> the query to execute. >> I would like to estimate the time without having to wa

Re: Behaviour when autovacuum is canceled

2018-09-13 Thread Tom Lane
=?UTF-8?q?Mart=C3=ADn_Fern=C3=A1ndez?= writes: > We basically started a VACUUM on a given table, waited for one index to > process (captured cleaned rows count) and cancel the VACUUM. When we run > another VACUUM on the same table the dead rows removed from the first index > was a number slight

Re: Behaviour when autovacuum is canceled

2018-09-13 Thread Martín Fernández
Tom, Thanks for the detailed explanation. I can start mapping your explanation with the source code I've been reading :) We are in the process of tuning our autovacuum settings (on some tables) and stop relying on crontabs that are performing manual vacuums.  By performing this changes we are