on 12/27/01 1:49, Christian Schmitz at support /at/ monkeybreadsoftware .D.O.T de wrote:
>>> Even if I know that each of those fields can't possibly be bigger than 32
>>> characters? Which leads me to another question, does the size of the
>>> varchar matter at all (as I assume you just use 4 bytes to keep the
>>> length)
>>
>> Yes, please look into Valentina kerel.pdf
BTW, Tuviah, more info:
Yes, VarChar store length of string, you are right.
Yes, VarChar size still play important role -- it regulate size of page for
file. When you say 504 bytes, page is 1024 bytes. For VarChar[10000] page is
20KB. Sinse page is smallest atom to read / write from disk size of page
will affect performance.
> Just an idea:
> would a pstring type save bytes?
>
> Instead of 4 bytes for length use one byte for varchars smaller than 256
> bytes. Would that save CPU time or disk space?
1) I really have made a mistake and now for VarChar is used LONG (4 bytes)
to keep length. Since there is limit on max length 65535 it was enough to
use 2 bytes only.
In one of future version I will redo this.
This really can give benefit if we have many empty strings.
2) Yes you are right, that for small VarChar <256 bytes, it is possible to
use ONE byte. Benefit will be in range 1/256 .. 2.
May be later I will do this.
--
Best regards,
Ruslan Zasukhin
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