Re: [HACKERS] Optimizer fed bad data about some system-table indexes

> > I'd say this whole mechanism is unnecessary; we should just build
> > the data on-the-fly the way it's done in write_irels(), and eliminate
> > all the file reading and writing code in init_irels and write_irels.
> > The only thing it could possibly be doing for us is saving some backend
> > startup time, but I'm not able to measure any difference when I delete
> > the init file.
> > 
> > I'll work on that tomorrow, unless I hear squawks of outrage from
> > someone who remembers what this code was for.
> 
> Hmm.  If you can get it to work without the file, great, or you could
> just delete the file when vacuum is performed, so the next backend
> recreates the file.  That would work too.

One other cache thing I want to do is enable index lookups on cache
failure for tables like pg_operator, that didn't use index lookups in
the cache because you didn't have multi-key system tables.

If you are looking for a single row, does anyone know when it is faster
to do a sequential scan, and when it is faster to do an index lookup
into the table.

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