Обсуждение: How To free resources used by large object Relations?

Hi,

I've changed the large object memory managment strategy to ensure that
each large object has it's own memory context.
This way I can free all memory for a large object when I lo_close
is called for it's oid. This seems to work.

I've noticed that the heap_close function used to close the heap used
by a large object doesn't really do any thing. (It calls RelationClose
which decrements some reference count).

Somehow I have to free the relation from the cache in the following
situations:
1. In a transaction I must free the stuff when the transaction is
commited/aborted.
2. Otherwise it must happen when lo_close is called.

Is this right?

Can anyone point me in the right direction?

Thanks Maurice.

>
> Hi,
>
> I've changed the large object memory managment strategy to ensure that
> each large object has it's own memory context.
> This way I can free all memory for a large object when I lo_close
> is called for it's oid. This seems to work.

This is a good idea.

>
> I've noticed that the heap_close function used to close the heap used
> by a large object doesn't really do any thing. (It calls RelationClose
> which decrements some reference count).
>
> Somehow I have to free the relation from the cache in the following
> situations:
> 1. In a transaction I must free the stuff when the transaction is
> commited/aborted.
> 2. Otherwise it must happen when lo_close is called.
>
> Is this right?
>

Beats me.

--
Bruce Momjian
maillist@candle.pha.pa.us

Maurice Gittens wrote:
>
> Hi,
>
> I've changed the large object memory managment strategy to ensure that
> each large object has it's own memory context.
> This way I can free all memory for a large object when I lo_close
> is called for it's oid. This seems to work.
>
> I've noticed that the heap_close function used to close the heap used
> by a large object doesn't really do any thing. (It calls RelationClose
> which decrements some reference count).
>
> Somehow I have to free the relation from the cache in the following
> situations:
> 1. In a transaction I must free the stuff when the transaction is
> commited/aborted.

Backend does it, don't worry.

> 2. Otherwise it must happen when lo_close is called.

It seems that you can't remove relation from cache untill
commit/abort, currently: backend uses local cache to unlink
files of relations created in transaction if abort...
We could change relcache.c:RelationPurgeLocalRelation()
to read from pg_class directly...

But how many LO do you create in single xact ?
Is memory allocated for cache so big ?

Vadim