Re: Performance (was: The New Slashdot Setup (includes MySql server))

Hi,

Hiroshi Inoue:
> 
> Maybe shared buffer isn't so large as to keep all the(4.1M) pg_index pages.

That seems to be the case.

> So it would read pages from disk every time, Unfortunately pg_index
> has no index to scan the index entries of a relation now.
> 
Well, it's reasonable that you can't keep an index on the table which
states what the indices are. ;-)

... on the other hand, Apple's HFS file system stores all the information
about the on-disk locations of their files as a B-Tree in, in, you
guessed it, a B-Tree which is saved on disk as an (invisible) file.
Thus, the thing stores the information on where its sectors are located
at, inside itself.
To escape this catch-22 situation, the location of the first three
extents (which is usually all it takes anyway) is stored elsewhere.

Possibly, something like this would work with postgres too.

> However why is pg_index so large ?
> 
Creating ten thousand tables will do that to you.

Is there an option I can set to increase the appropriate cache, so that
the backend can keep the data in memory?

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