Re: query a table with lots of coulmns

On 19 September 2014 13:51, Björn Wittich <Bjoern_Wittich@gmx.de> wrote:

Hi mailing list,

I am relatively new to postgres. I have a table with 500 coulmns and about 40 mio rows. I call this cache table where one column is a unique key (indexed) and the 499 columns (type integer) are some values belonging to this key.

Now I have a second (temporary) table (only 2 columns one is the key of my cache table) and I want  do an inner join between my temporary table and the large cache table and export all matching rows. I found out, that the performance increases when I limit the join to lots of small parts.
But it seems that the databases needs a lot of disk io to gather all 499 data columns.
Is there a possibilty to tell the databases that all these colums are always treated as tuples and I always want to get the whole row? Perhaps the disk oraganization could then be optimized?

 

Hi,
do you have indexes on the columns you use for joins?

Szymon