RE: transaction safety

OK, someone want to answer this? I have always been under the impression
that Postgres would not block under these circumstances, however, this is
clearly blocking, for no apparently good reason.

I have just run a test on my own server, and this blocking does not happen.
Both sessions run independently until each has committed, then displaying
information from the other insert, but definitely not blocking. It works
exactly as I would have expected.

Anybody???

MikeA

-----Original Message-----
From: DaVinci [mailto:bombadil(at)wanadoo(dot)es]
Sent: 13 February 2001 10:42
To: Lista PostgreSql
Subject: Re: [GENERAL] transaction safety

On Tue, Feb 13, 2001 at 09:56:18AM -0000, Michael Ansley wrote:
> Hi,
>
> Well, the number is 'locked', because once it's given to you, that's it,
> it's gone from the 'list of available numbers' (i.e.: the sequence).
> However, between the insert, and the read of the ID, if another
transaction
> performs an insert, it does NOT affect the ID that the first transaction
> reads (i.e.: your ID read in the first transaction IS definitely still
safe,
> it will still read the correct one).

I understand this.

> AND, the first insert does NOT block
> the second insert. The second insert could complete and commit before the
> first one.

But I don't know how to reproduce this part.

If I have two different sessions of psql connected to same database:

psql-1# begin;
psql-2# begin;
psql-1# insert into foo ...;
psql-2# insert into foo ...; <- ¡¡¡Frozen!!!
psql-1# commit; <- psql-2 unfrozen

Why I get this?.

> Does this explain better?

Very well, thanks ;)

David

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