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List:Internals« Previous MessageNext Message » Date:February 19 2007 11:13am
Subject:BLOB implementation for heap engine
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I'm a senior student at university of Roma 3; I'm doing a thesis aiming to provide a
better sinergy between Grass and MySQL (using the 
fast all in memory engine); I found that heap engine doesn't support Gis Data because of
the absence of Blob support, through which GIS 
data are, at the moment, stored. I also found that blob data aren't supported because
memory engine has a fixed row format, which is 
incompatible with blobs.

Writing on mysql forums (,130771,130771#msg-130771)
this idea is growing up:

>Your idea sounds interesting. I added to our internal todo list:
>Add a pointer to the fixed length record for every blob. Store the blob elsewhere.
> While records are stored bottom up in >the tables 
memory pool, we could perhaps allocate blobs top down. The table is full when they meet in
the middle. To >reduce fragmentation, we could 
store the blobs in chunks of record size. Perhaps even link them in a chain so that
>fragments can be reused. OPTIMIZE could move lower 
fragments up into gaps so that more records can be added.
>The charm of the idea is that we won't need to implement "real" variable length
> records. This should make things much >simpler.

Ingo has got the point of my idea: the fixed lenght row format would remain, just the blob
column size would be the lenght of memory 
address in which a pointer to elsewhere in memory may be memorized to retreive real data
of the blob.

I'm working with 5.1.15-beta source code. It seems to me that the obvious way to start is
to add hp_blobs.c (hp_blobs.h) to the "mysql-
5.1.15-beta/storage/heap", but it could not be so. Which other files and parts of the code
would be interested in this modification and 
should be analyzed/modified?

I hope to read from you all soon. Thanks.

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BLOB implementation for heap engineciccettino@tiscali.it19 Feb
  • Re: BLOB implementation for heap engineGiuseppe Maxia19 Feb
  • Re: BLOB implementation for heap engineIngo Strüwing19 Feb
Re: BLOB implementation for heap engineciccettino@tiscali.it1 Mar
  • Re: BLOB implementation for heap engineMark Callaghan1 Mar
    • Re: BLOB implementation for heap engineIngo Strüwing1 Mar
      • Re: BLOB implementation for heap engineIngo Strüwing1 Mar
  • Re: BLOB implementation for heap engineSergei Golubchik1 Mar
Re: BLOB implementation for heap engineciccettino@tiscali.it7 Mar
  • Re: BLOB implementation for heap engineIngo Strüwing8 Mar