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List:       kde-pim
Subject:    Re: [Kde-pim] Akonadi db schema change needed to store search folder queryStrings
From:       Will Stephenson <wstephenson () kde ! org>
Date:       2012-02-24 13:18:35
Message-ID: 1371009.lC7GoMnUTp () emsig
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On Friday 24 Feb 2012 13:28:06 you wrote:
> On Friday 24 February 2012 09:52:37 Will Stephenson wrote:
> > On Thursday 23 Feb 2012 22:26:49 Shaheed Haque wrote:
> > > Is the extra storage really a concern? I suppose the pimitemtable is
> > > probably going to have most entries by far. That seems to have a
> > > handful of columns which might be strings (and 9 in total). Even if I
> > > had a million records, we are talking a handful of MB.
> > > 
> > > That seems perfectly reasonable...Or have I misunderstood?
> > 
> > Multiplying the number of rows by the number of QString columns and
> > summing
> > it across all tables gives me (2 imap accounts, about 2.5GB mail in total
> > on the servers) an additional 1455755 bytes for the storage. Then I assume
> > indexed columns count double, which gives another 872906 * 2 bytes as
> > there
> > are 2 indices on parttable.name (which contains a lot of repeated entries,
> > perhaps it would make sense to normalize this out into its own table?).
> > 
> > That's 3201567 extra bytes in theory.  I'm not a database guy so don't
> > know
> > how that translates into real extra storage, memory footprint (indexes
> > stay
> > in memory, right?) and performance.  Can someone better informed comment?
> 
> VARBINARY has variable length, hence it will only use as much as it actually
> needs. The number you pass it is the maximum size.

I'm on kde-pim@, no need to CC me.

In my reading of the manual, VARBINARY has the same storage requirements as 
VARCHAR, which means, it requires length(data) bytes, plus one byte for len 
<=255, else plus 2 bytes.  It's in the manual.  I suppose it uses either a 
byte or a short for the field length.  

Will
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