Re: proposal: lob conversion functionality

On 12.08.2013 21:08, Pavel Stehule wrote:

2013/8/10 Tom Lane<tgl@sss.pgh.pa.us>:

Pavel Stehule<pavel.stehule@gmail.com>  writes:

I found so there are no simple API for working with LO from PL without
access to file system.

What?  See lo_open(), loread(), lowrite(), etc.

yes, so there are three problems with these functions:

a) probably (I didn't find) undocumented

It's there, although it's a bit difficult to find by searching. See: http://www.postgresql.org/docs/devel/static/lo-funcs.html.

I don't actually agree with this phrase on that page:

The ones that are actually useful to call via SQL commands are
lo_creat, lo_create, lo_unlink, lo_import, and lo_export

Calling lo_open, loread and lowrite seems equally useful to me.

b) design with lo handler is little bit PL/pgSQL unfriendly.

It's a bit awkward, I agree.

c) probably there is a bug - it doesn't expect handling errors

postgres=# select fbuilder.attachment_to_xml(0);
WARNING:  Snapshot reference leak: Snapshot 0x978f6f0 still referenced
  attachment_to_xml
───────────────────
  [null]
(1 row)

Yeah, that's a server-side bug. inv_open() registers the snapshot before checking if the large object exists. If it doesn't, the already-registered snapshot is not unregistered, hence the warning.

I've committed the attached fix for that bug.

- Heikki