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From:Hagen Höpfner Date:February 19 2006 12:25pm
Subject:Re: MYI ... Basedata ...
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>> ------------------------------------------------------------
>>   mi_int4store(ptr,base->pack_reclength);        ptr +=4;
>> Is this the average for a packed record? If so, how is it computed? If I
>> do not pack the data file, then pack_reclength is equal to reclength,
>> isn't it?
>
> How it's computed - see mi_create.c.
> It's equal if there's no live checksum, and pack_reclength
> is not less than rec_reflength.
>
> Not the average, it's basically the reclength above without
> rec_reflength/checksum correction.
Hm, I looked at the source code and found:

  share.base.reclength=real_reclength;
  share.base.pack_reclength=reclength+ test(options & HA_OPTION_CHECKSUM);

For me this looks like that pack_reclength is the reclength WITH
corrections. However, as longer as I think about the MyISAM driver as
more obvious is the question, what "pack" means exactly. Does it
really mean compression or only the way of representing (uncompressed)
the data in main memory?

All the best,

Hagen

- --
- ------------------------------------------------------------
Dr.-Ing. Hagen Höpfner | hoepfner@stripped | +49 7251 700 239
- ------------------------------------------------------------
         http://www.i-u.de/schools/hopfner/index.html

             International University in Germany
               School of Information Technology
                  Campus 3  D-76646 Bruchsal
- ------------------------------------------------------------
Information about the German textbook  on  "Mobile Databases
and   Information   Systems"  by   H. Höpfner, C. Türker and
B. König-Ries are available at http://www.dpunkt.de/.
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Thread
MYI ... Basedata ...Hagen Höpfner19 Dec
  • Re: MYI ... Basedata ...Sergei Golubchik19 Dec
    • Re: MYI ... Basedata ...Hagen Höpfner3 Feb
      • Re: MYI ... Basedata ...Sergei Golubchik7 Feb
    • Re: MYI ... Basedata ...Hagen Höpfner20 Feb
      • Re: MYI ... Basedata ...Sergei Golubchik20 Feb
        • Packed Data in MyISAMHagen Höpfner23 Feb
          • Re: Packed Data in MyISAMSergei Golubchik23 Feb
            • Re: Packed Data in MyISAMHagen Höpfner23 Feb
              • Re: Packed Data in MyISAMSergei Golubchik24 Feb