[doc] Blob compression

[Ruslan Zasukhin]

on 8/8/03 4:13, Erik Mueller-Harder at lists at praxisworks.com wrote:

> Hi, Ruslan --
> 
> The Valentina Database Kernel documentation (page 27) says this about the
> VBlob class:
> 
> € On default Valentina uses ZIP compression.
> € You can set up level of compression in range 0..9.
>   0 - fastest compression.
>   9 - best compression.
> 
> I know how to turn compression on and off with the "compressed" property, but
> I don't see how to change the compression level.
> 
> I do see that VPictures have a "quality" compression parameter of 0 to 100,
> but I'm storing text in a VText subclass of VBlob, not (of course!) in
> VPicture.
> 
> Are there levels of compression for the VText subclass of VBlob?  How does one
> access it?  What's the default?  Is it merely a case of speed versus degree of
> compression?
> 
> Thanks for your clarification,

Hi Erik,

Yes compression works for TEXT field also.
Actually built-in compression have sense ONLY for TEXT field, because it can
have indexes.

For simple BLOBs you can use your OWN ZIP compresin, and then store in BLOB
field ALREADY compressed data.

For TEXT this will not work, because Valentina self must be able extract
data to index them. you see?


2) I cannot find in API way to control compression level. Strange.
Default probably is 4.
I need check more this.

-- 
Best regards,
Ruslan Zasukhin      [ I feel the need...the need for speed ]
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e-mail: ruslan at paradigmasoft.com
web: http://www.paradigmasoft.com

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