On Sep 29, 2008, at 6:16 AM, [EMAIL PROTECTED] wrote:
The hstore module, as I said,looks really cool, I've contemplated something like it. I have a module provides a set of accessors for an XML text column that works similarly, but it parses the XML on each access and the application has to create theXML. (I have XML creation modules for Java, PHP, C++, and standard C bindings.)
Yeah, "ad-hoc" storage is always a huge problem in databases. For years the only way to do it was with EAV, which is tricky at best.
In my experience, there typically isn't an un-bounded set of possible attribute names. It's usually fairly constrained, but the problem is that you never know when a new one will just pop up.
It's very common right now for people to use either XML or YAML to deal with this. That has it's own set of problems.
There's a few major improvements to be had here:1: We should have a flexible storage mechanism that can either be used with it's own native syntax, or can interface to other hash formats such XML or YAML. Of course, both XML and YAML allow an obscene amount of nesting, etc, but generally people are only using these in a very simple form to emulate a hash table. It would be interesting to allow casting hstore to and from other proprietary hash formats as well, such as perl hashes.
2: Storage of attribute names can quickly become *very* expensive. Even with short 6-10 character names, you can easily end up using half the storage for just attribute names. I'd like to see hstore support storing attribute names in a lookup table, or using some other means to reduce the storage overhead.
3: Related to #2, storing numbers stinks because you end up burning 1 byte per digit. Some concept of data type for an attribute would improve this.
Sadly, I don't have time to work on any of this. But these things are issues to my company, and we do have money. ;)
-- Decibel!, aka Jim C. Nasby, Database Architect [EMAIL PROTECTED] Give your computer some brain candy! www.distributed.net Team #1828
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