Re: [HACKERS] What about LIMIT in SELECT ?

> > I have had more time to think about this.  Basically, for pre-sorted
> > data, our psort code is very fast, because it does not need to sort
> > anything.  It just moves the rows in and out of the sort memory.  Yes,
> > it could be removed in some cases, and probably should be, but it is not
> > going to produce great speedups.
> 
>     And I got the time to hack around about this.
> 
>     I  hacked  in  a little check into the planner, that compares
>     the sortClause against the key field list of  an  index  scan
>     and  just  suppresses  the sort node if it exactly matchs and
>     all sort operators are "<".
> 
>     I tested with a 10k row table where key is a text field.  The
>     base query is a
> 
>         SELECT ... WHERE key > 'val' ORDER BY key;
> 
>     The  used 'val' is always a key that is close to the first of
>     all keys in the table ('' on the first  query  and  the  last
>     selected value on subsequent ones).

This is good stuff.  I want to think about it for a day.  Sounds very
promising.


-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  maillist@candle.pha.pa.us            |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026