Обсуждение: Large objects - bug? caveat? feature?

I am using PHP3 with Apache on top of Linux, using beta 2 of PostgreSQL. I
have uncovered an interesting (bug/feature?) in the Large Objects.

If (using PHP3) you write out, say, a 2,000 byte large object (a text
article in this case), and then using an edit routine you replace that 2,000
object with a more concise, edited 1,000-byte document, what you get is the
1,000-bytes of the edit, followed by the final 1,000 bytes of the original
2,000 byte article. In other words, it doesn't shrink the file to the edited
size.

Secondly, I notice that in my data/base/... area that whenever I create an
object it creates a single file on the disk. Does that mean that if I have
100,000 articles in my knowledge base, that it is possible that I will have
100,000 files individual 8-to-10k files on my hard drive? Does Linux suffer
degradation in performance when having that many files in a directory?

Justin


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Justin Long wrote:

> 2,000 byte article. In other words, it doesn't shrink the file > to the edited size.

Does the interface have any equivilent to the UNIX O_TRUNC?

> Secondly, I notice that in my data/base/... area that whenever I create an
> object it creates a single file on the disk. Does that mean that if I have
> 100,000 articles in my knowledge base, that it is possible that I will have
> 100,000 files individual 8-to-10k files on my hard drive?

It's worse than that I think. I believe you get _two_ files for each
large object. Large objects really suck badly.

> Does Linux suffer
> degradation in performance when having that many files in a 
> directory?

Absolutely does suffer. Even worse, your regular database tables are in
the same directory, so they'll suffer too. Another problem, is pgdump
doesn't dump large objects so you have to figure out some other backup
strategy.

-- 
Chris Bitmead
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mailto:chris.bitmead@bigfoot.com