[CDBI] mysql compress support

William Ross will at spanner.org
Tue Aug 30 13:40:01 BST 2005

On 29 Aug 2005, at 02:15, Ilia Lobsanov wrote:

> Hello,
> How would I seamlessly use mysql's 'compress' string function (zlib
> integration) with Class::DBI?
> By "seamlessly", I mean I want Class::DBI to compress/uncompress upon
> insert/select using the mysql syntax.

There are a few options, depending on how widely you want this to  
happen, but they're not very nice. Class::DBI encourages a few kinds  
of modification but makes any others very difficult. You can't even  
do this by overriding the standard sql statements because they tend  
to just use a %s placeholder for all their parameters, and cdbi's  
storage or retrieval operations usually take the form sql_Foo(join 
(columns)), like this line in _flesh():

     @row{@want} = $self->sql_Flesh(join ", ", @want)->select_row 

What you really want is to insert a map block in that join statement  
and expand each parameter to include the decompression syntax. You'd  
have to override them one by one. Not a small job.

Here are some ideas, anyway:

1. subclass or replace DBIx::ContextualFetch and (selectively?)  
modify query parameters to add the compress and decompress syntax.  
This will be quite messy and very sensitive to cdbi versions, but it  
should work.

2. improve Class::DBI's subclassability and submit patches to Tony.  
This probably just means adding an empty method call or two to the  
preparation of each statement, and should be quite easy to do even  
though it affects a great many lines.

3. wait for the interesting but slow refactoring of Class::DBI that  
should follow the release of version 1, if Tony has any enthusiasm  
left. It will bring more structure to columns and attributes and  
should provide the sort of hook you need.

4. investigate the alternative ORM solutions, especially John  
Siracusa's Rose::DB, which I think is turning into a better choice  
than cdbi. It already has a much better object structure and looks  
like it will offer the sort of hook you need to tweak column  
retrieval very easily. I haven't used it properly yet so can't be sure.

I actually quite like number 2, especially as Tony is working on a  
release. I'd like to see more low-level hooks in the sql generation.  
He has said that v1 will only see bug fixes rather than new features,  
though: you should definitely talk to him before doing any work.

Sorry I can't see an easier answer,


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