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Thread: create table as select VS create table; insert as select

create table as select VS create table; insert as select

From
Jacqui Caren-home
Date:
I have inherited an application that populates a number of
temp.y tables using create table ... as select ...

This is taking roughly five to ten minutes to run

As this process hammers the database, I can only run benchmarks at night so
am asking here if anyone know if

create table ...; then insert into ... as select... ; would be faster.

or if anyone can suggest an alternative I may have missed.

I am happy to move code server side if need be.

TIA

Jacqui

I know these is not a lot of detail in the above - the system is under NDA
and I need to check with my employer before I give out any system details.

Before you ask it is not a big customer - just a very paranoid one :-)

Re: create table as select VS create table; insert as select

From
Sergey Konoplev
Date:
Hi,

On 29 October 2010 11:46, Jacqui Caren-home <jacqui.caren@ntlworld.com> wrote:
> I have inherited an application that populates a number of
> temp.y tables using create table ... as select ...

What is the principle of creating this temp.y tables?
May be table partitioning is better to implement here -
http://www.postgresql.org/docs/8.4/interactive/ddl-partitioning.html

>
> This is taking roughly five to ten minutes to run
>
> As this process hammers the database, I can only run benchmarks at night so
> am asking here if anyone know if
>
> create table ...; then insert into ... as select... ; would be faster.
>
> or if anyone can suggest an alternative I may have missed.
>
> I am happy to move code server side if need be.
>
> TIA
>
> Jacqui
>
> I know these is not a lot of detail in the above - the system is under NDA
> and I need to check with my employer before I give out any system details.
>
> Before you ask it is not a big customer - just a very paranoid one :-)
>
>
>
> --
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--
Sergey Konoplev

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Re: create table as select VS create table; insert as select

From
Tom Lane
Date:
Jacqui Caren-home <jacqui.caren@ntlworld.com> writes:
> I have inherited an application that populates a number of
> temp.y tables using create table ... as select ...
> As this process hammers the database, I can only run benchmarks at night so
> am asking here if anyone know if
> create table ...; then insert into ... as select... ; would be faster.

No, it'd likely be slower --- possibly quite a bit slower.

When you say "temp-y", do you mean these are in fact TEMP tables?
If not, can you make them be so?  That would help.

            regards, tom lane