Thread: Temporary tables and in-memory use

Hello,<br /><br />If I'm not wrong, temporary tables stay in memory if they do not go over temp_buffers limit (e.g. if
temp_buffersis 2GB and the size of the table is 300MB the table will remain in memory).<br />What if a column is
variablelength (e.g. text), how does this column stay in-memory since it should be stored in TOAST?<br /> When I build
aGiST index on a temporary table does the index stay in memory as well?<br /><br />Thank you,<br />Marios<br /> 

Marios Vodas <mvodas@gmail.com> writes:
> If I'm not wrong, temporary tables stay in memory if they do not go over
> temp_buffers limit (e.g. if temp_buffers is 2GB and the size of the table is
> 300MB the table will remain in memory).
> What if a column is variable length (e.g. text), how does this column stay
> in-memory since it should be stored in TOAST?

Well, the toast table is also temp, so it'll get cached in temp_buffers
as well, as long as it fits.

> When I build a GiST index on a temporary table does the index stay in memory
> as well?

Same answer.

Keep in mind that temp_buffers is per process, not global.  Just as with
work_mem, you need to be careful about setting it sky-high.
        regards, tom lane

Thank you. The setup is intended for one user environment for complex 
queries and operations that's why I wrote 2GB temp_buffers!
Thank you again, I really appreciate it.
Marios

On 29/9/2011 7:55 μμ, Tom Lane wrote:
> Marios Vodas<mvodas@gmail.com>  writes:
>> If I'm not wrong, temporary tables stay in memory if they do not go over
>> temp_buffers limit (e.g. if temp_buffers is 2GB and the size of the table is
>> 300MB the table will remain in memory).
>> What if a column is variable length (e.g. text), how does this column stay
>> in-memory since it should be stored in TOAST?
> Well, the toast table is also temp, so it'll get cached in temp_buffers
> as well, as long as it fits.
>
>> When I build a GiST index on a temporary table does the index stay in memory
>> as well?
> Same answer.
>
> Keep in mind that temp_buffers is per process, not global.  Just as with
> work_mem, you need to be careful about setting it sky-high.
>
>             regards, tom lane