Re: [HACKERS] regression bigtest needs very long time

SAKAIDA Masaaki wrote:

>    There are no problem concerning the NUMERIC test of INSERT/
> SELECT and add/subtract/multiply/division. The only problem is
> the processing time.
>
>    One solution which solves this problem is to change the argument
> into *float8*. If the following changes are done, the processing
> will become high-speed than a previous about 10 times.
>
>    File     :"src/regress/sql/numeric.sql"
>    Statement:"INSERT INTO num_result SELECT id, 0,
>                   POWER('10'::numeric,LN(ABS(round(val,300))) ..."
>
>    Change:   "LN(ABS(round(val,300))))"
>        to:   "LN(float8(ABS(round(va,300))))"
>
>
>
> # Another solution is to automatically convert the argument of the
>   LOG function into double precision data type in the *inside*.
>  (But, I do not know what kind of effect will be caused by this
>   solution.)

    The  complex  functions  (LN,  LOG, EXP, etc.) where added to
    NUMERIC for the case someone really  needs  higher  precision
    than  float8.   The  numeric_big  test  simply  ensures  that
    someone really get's the  CORRECT  result  when  computing  a
    logarithm  up to hundreds of digits. All the expected results
    fed into the tables are computed by scripts using bc(1)  with
    a  precision  200  digits  higher  than that used in the test
    itself. So I'm  pretty  sure  NUMERIC  returns  a  VERY  GOOD
    approximation  if  I  ask  for the square root of 2 with 1000
    digits.

    One thing in mathematics that is  silently  forbidden  is  to
    present  a result with digits that aren't significant! But it
    is the user to decide where the  significance  of  his  INPUT
    ends,  not  the  database.  So it is up to the user to decide
    when to loose precision by switching to float.


Jan

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