Thread

1. Learning EXPLAIN

   Flávio Henrique <yoshimit@gmail.com> — 2017-12-08T01:12:16Z

   Hi experts!
   
   I read this nice article about Understanding EXPLAIN [1] weeks ago that
   opened my mind about the tool, but it seems no enough to explain a lot of
   plans that I see in this list.
   
   I often read responses to a plan that are not covered by the article.
   
   I need/want to know EXPLAIN better.
   
   Can you kindly advise me a good reading about advanced EXPLAIN?
   
   Thank you!
   
   
   [1] http://www.dalibo.org/_media/understanding_explain.pdf
   
   Flávio Henrique
   

2. Re: Learning EXPLAIN

   Guillaume Lelarge <guillaume@lelarge.info> — 2017-12-08T13:20:16Z

   Hi,
   
   2017-12-08 2:12 GMT+01:00 Flávio Henrique <yoshimit@gmail.com>:
   
   > Hi experts!
   >
   > I read this nice article about Understanding EXPLAIN [1] weeks ago that
   > opened my mind about the tool, but it seems no enough to explain a lot of
   > plans that I see in this list.
   >
   
   Thanks.
   
   I often read responses to a plan that are not covered by the article.
   >
   > I need/want to know EXPLAIN better.
   >
   > Can you kindly advise me a good reading about advanced EXPLAIN?
   >
   >
   There's not much out there. This document was written after reading this
   list, viewing some talks (you may find a lot of them on youtube), and
   reading the code.
   
   I intend to update this document, since I learned quite more since 2012.
   Though I didn't find the time yet :-/
   
   Anyway, thanks.
   
   
   -- 
   Guillaume.
   

3. Re: Learning EXPLAIN

   Flavio Henrique Araque Gurgel <fhagur@gmail.com> — 2017-12-08T13:32:06Z

   Em sex, 8 de dez de 2017 às 14:20, Guillaume Lelarge <guillaume@lelarge.info>
   escreveu:
   
   > Hi,
   >
   > 2017-12-08 2:12 GMT+01:00 Flávio Henrique <yoshimit@gmail.com>:
   >
   >> Hi experts!
   >>
   >> I read this nice article about Understanding EXPLAIN [1] weeks ago that
   >> opened my mind about the tool, but it seems no enough to explain a lot of
   >> plans that I see in this list.
   >>
   >
   > Thanks.
   >
   > I often read responses to a plan that are not covered by the article.
   >>
   >> I need/want to know EXPLAIN better.
   >>
   >> Can you kindly advise me a good reading about advanced EXPLAIN?
   >>
   >>
   > There's not much out there. This document was written after reading this
   > list, viewing some talks (you may find a lot of them on youtube), and
   > reading the code.
   >
   > I intend to update this document, since I learned quite more since 2012.
   > Though I didn't find the time yet :-/
   >
   > Anyway, thanks.
   >
   >
   Hello all
   
   I would like to make clear that there are two "Flavio Henrique" on the
   lists, me beeing one of them, I'd like to say that I'm not the OP.
   A bit off-topic anyway, thanks for understanding.
   
   Flavio Gurgel
   

4. Re: Learning EXPLAIN

   Gustavo Velasquez <gustavojunior@gmail.com> — 2017-12-08T16:44:50Z

   Dude,
   
   You can rest assured that at least the Brazilians members will always know
   based on your last name you are not the same :-).
   
   What's the point of explaining that anyways? Got curious.
   
   As to what pertains to the topic:
   
   This is another simple yet effective doc:
   
   https://wiki.postgresql.org/images/4/45/Explaining_EXPLAIN.pdf
   
   Execution plans are tricky and reading them accurately to make good
   decisions require a lot of experience and awareness of the situation. It
   does not only require that you know how to read the tool itself but also
   know how the DB and schemas have been designed, if stats are up to date,
   how tables are populated, frequency and type of queries, adequate indexing
   in place, the hardware it sits on, etc.
   
   It's a mix of science, broaden knowledge, perspicacity, and why not
   say, it's an art.
   
   Have a great weekend.
   
   ___________________________________________________________________________
   Gustavo Velasquez
   +1 (256) 653-9725
   
   
   On Fri, Dec 8, 2017 at 7:32 AM, Flavio Henrique Araque Gurgel <
   fhagur@gmail.com> wrote:
   
   >
   > Em sex, 8 de dez de 2017 às 14:20, Guillaume Lelarge <
   > guillaume@lelarge.info> escreveu:
   >
   >> Hi,
   >>
   >> 2017-12-08 2:12 GMT+01:00 Flávio Henrique <yoshimit@gmail.com>:
   >>
   >>> Hi experts!
   >>>
   >>> I read this nice article about Understanding EXPLAIN [1] weeks ago that
   >>> opened my mind about the tool, but it seems no enough to explain a lot of
   >>> plans that I see in this list.
   >>>
   >>
   >> Thanks.
   >>
   >> I often read responses to a plan that are not covered by the article.
   >>>
   >>> I need/want to know EXPLAIN better.
   >>>
   >>> Can you kindly advise me a good reading about advanced EXPLAIN?
   >>>
   >>>
   >> There's not much out there. This document was written after reading this
   >> list, viewing some talks (you may find a lot of them on youtube), and
   >> reading the code.
   >>
   >> I intend to update this document, since I learned quite more since 2012.
   >> Though I didn't find the time yet :-/
   >>
   >> Anyway, thanks.
   >>
   >>
   > Hello all
   >
   > I would like to make clear that there are two "Flavio Henrique" on the
   > lists, me beeing one of them, I'd like to say that I'm not the OP.
   > A bit off-topic anyway, thanks for understanding.
   >
   > Flavio Gurgel
   >
   >
   

5. Re: Learning EXPLAIN

   Samuel Gendler <sgendler@ideasculptor.com> — 2017-12-09T04:47:13Z

   What about the many-part explanation posted on the blog that accompanies
   explain.depesz.com.  Here is the first installment. I seem to remember that
   there are 5 or 6 installments.
   
   https://www.depesz.com/2013/04/16/explaining-the-unexplainable/
   
   On Fri, Dec 8, 2017 at 8:44 AM, Gustavo Velasquez <gustavojunior@gmail.com>
   wrote:
   
   > Dude,
   >
   > You can rest assured that at least the Brazilians members will always know
   > based on your last name you are not the same :-).
   >
   > What's the point of explaining that anyways? Got curious.
   >
   > As to what pertains to the topic:
   >
   > This is another simple yet effective doc:
   >
   > https://wiki.postgresql.org/images/4/45/Explaining_EXPLAIN.pdf
   >
   > Execution plans are tricky and reading them accurately to make good
   > decisions require a lot of experience and awareness of the situation. It
   > does not only require that you know how to read the tool itself but also
   > know how the DB and schemas have been designed, if stats are up to date,
   > how tables are populated, frequency and type of queries, adequate indexing
   > in place, the hardware it sits on, etc.
   >
   > It's a mix of science, broaden knowledge, perspicacity, and why not
   > say, it's an art.
   >
   > Have a great weekend.
   >
   > ____________________________________________________________
   > _______________
   > Gustavo Velasquez
   > +1 (256) 653-9725 <(256)%20653-9725>
   >
   >
   > On Fri, Dec 8, 2017 at 7:32 AM, Flavio Henrique Araque Gurgel <
   > fhagur@gmail.com> wrote:
   >
   >>
   >> Em sex, 8 de dez de 2017 às 14:20, Guillaume Lelarge <
   >> guillaume@lelarge.info> escreveu:
   >>
   >>> Hi,
   >>>
   >>> 2017-12-08 2:12 GMT+01:00 Flávio Henrique <yoshimit@gmail.com>:
   >>>
   >>>> Hi experts!
   >>>>
   >>>> I read this nice article about Understanding EXPLAIN [1] weeks ago that
   >>>> opened my mind about the tool, but it seems no enough to explain a lot of
   >>>> plans that I see in this list.
   >>>>
   >>>
   >>> Thanks.
   >>>
   >>> I often read responses to a plan that are not covered by the article.
   >>>>
   >>>> I need/want to know EXPLAIN better.
   >>>>
   >>>> Can you kindly advise me a good reading about advanced EXPLAIN?
   >>>>
   >>>>
   >>> There's not much out there. This document was written after reading this
   >>> list, viewing some talks (you may find a lot of them on youtube), and
   >>> reading the code.
   >>>
   >>> I intend to update this document, since I learned quite more since 2012.
   >>> Though I didn't find the time yet :-/
   >>>
   >>> Anyway, thanks.
   >>>
   >>>
   >> Hello all
   >>
   >> I would like to make clear that there are two "Flavio Henrique" on the
   >> lists, me beeing one of them, I'd like to say that I'm not the OP.
   >> A bit off-topic anyway, thanks for understanding.
   >>
   >> Flavio Gurgel
   >>
   >>
   >
   

6. Re: Learning EXPLAIN

   Samuel Gendler <sgendler@ideasculptor.com> — 2017-12-09T04:52:36Z

   Ah, I see now that the article you linked to in the OP is written by the
   same author and is maybe the very same content. If so, that sure seems
   pretty comprehensive to me, though I've also been reading this list, off
   and on, for many years, which has probably filled a lot of the gaps left by
   the original blog posts.
   
   On Fri, Dec 8, 2017 at 8:47 PM, Sam Gendler <sgendler@ideasculptor.com>
   wrote:
   
   > What about the many-part explanation posted on the blog that accompanies
   > explain.depesz.com.  Here is the first installment. I seem to remember
   > that there are 5 or 6 installments.
   >
   > https://www.depesz.com/2013/04/16/explaining-the-unexplainable/
   >
   > On Fri, Dec 8, 2017 at 8:44 AM, Gustavo Velasquez <gustavojunior@gmail.com
   > > wrote:
   >
   >> Dude,
   >>
   >> You can rest assured that at least the Brazilians members will always
   >> know based on your last name you are not the same :-).
   >>
   >> What's the point of explaining that anyways? Got curious.
   >>
   >> As to what pertains to the topic:
   >>
   >> This is another simple yet effective doc:
   >>
   >> https://wiki.postgresql.org/images/4/45/Explaining_EXPLAIN.pdf
   >>
   >> Execution plans are tricky and reading them accurately to make good
   >> decisions require a lot of experience and awareness of the situation. It
   >> does not only require that you know how to read the tool itself but also
   >> know how the DB and schemas have been designed, if stats are up to date,
   >> how tables are populated, frequency and type of queries, adequate indexing
   >> in place, the hardware it sits on, etc.
   >>
   >> It's a mix of science, broaden knowledge, perspicacity, and why not
   >> say, it's an art.
   >>
   >> Have a great weekend.
   >>
   >> ____________________________________________________________
   >> _______________
   >> Gustavo Velasquez
   >> +1 (256) 653-9725 <(256)%20653-9725>
   >>
   >>
   >> On Fri, Dec 8, 2017 at 7:32 AM, Flavio Henrique Araque Gurgel <
   >> fhagur@gmail.com> wrote:
   >>
   >>>
   >>> Em sex, 8 de dez de 2017 às 14:20, Guillaume Lelarge <
   >>> guillaume@lelarge.info> escreveu:
   >>>
   >>>> Hi,
   >>>>
   >>>> 2017-12-08 2:12 GMT+01:00 Flávio Henrique <yoshimit@gmail.com>:
   >>>>
   >>>>> Hi experts!
   >>>>>
   >>>>> I read this nice article about Understanding EXPLAIN [1] weeks ago
   >>>>> that opened my mind about the tool, but it seems no enough to explain a lot
   >>>>> of plans that I see in this list.
   >>>>>
   >>>>
   >>>> Thanks.
   >>>>
   >>>> I often read responses to a plan that are not covered by the article.
   >>>>>
   >>>>> I need/want to know EXPLAIN better.
   >>>>>
   >>>>> Can you kindly advise me a good reading about advanced EXPLAIN?
   >>>>>
   >>>>>
   >>>> There's not much out there. This document was written after reading
   >>>> this list, viewing some talks (you may find a lot of them on youtube), and
   >>>> reading the code.
   >>>>
   >>>> I intend to update this document, since I learned quite more since
   >>>> 2012. Though I didn't find the time yet :-/
   >>>>
   >>>> Anyway, thanks.
   >>>>
   >>>>
   >>> Hello all
   >>>
   >>> I would like to make clear that there are two "Flavio Henrique" on the
   >>> lists, me beeing one of them, I'd like to say that I'm not the OP.
   >>> A bit off-topic anyway, thanks for understanding.
   >>>
   >>> Flavio Gurgel
   >>>
   >>>
   >>
   >