Re: Question when to use BEGIN / END - Mailing list pgsql-novice

This is the wrong place for a view. Use "CREATE LOCAL TEMPORARY TABLE" instead.

On Mon, 2009-11-30 at 10:32 +0100, Rikard Bosnjakovic wrote:

I have a case where I want to forbid a race condition. Basically, I have this:

$q = "CREATE VIEW foo AS ( SELECT * FROM foo WHERE [...different
conditions every call ...]  )";
@pg_query($db, $q);
$q = "SELECT * FROM foo";
$res = pg_query($db, $q);
$row = pg_fetch_object($res);
... change table foo...
$q = "DROP VIEW foo";
@pg_query($db, $q);

It is of utmost importance that there is not another client doing the
same thing while the above is running. When the DROP VIEW is done,
another client can start its work but not until then.

I'm reading about BEGIN/END on
http://www.postgresql.org/docs/7.4/interactive/sql-begin.html but I'm
not sure this is the solution. What I'm wondering is this: If I
prepend BEGIN on CREATE VIEW above, and append END after DROP VIEW,
can I still access the table foo in between? Or is BEGIN/END only
supposed to be used on queries that do INSERT or UPDATE, i.e. no
data-reading?


-- 
- Rikard

Mladen Gogala Sr. Oracle DBA 1500 Broadway New York, NY 10036 (212) 329-5251 www.vmsinfo.com The Leader in Integrated Media Intelligence Solutions