Re: [HACKERS] time stops within transaction

[Hiroshi Inoue]

Tom Lane wrote: > Hiroshi Inoue <[EMAIL PROTECTED]> writes: > >>>> Postgres doesn't have an idea of what a 'top-level' statement is? I.E. > >>>> statement as submitted by a client (libpq)? > >> > >> There's never been any reason to make such a distinction. > > > There's already a distinction. > > Snapshot is made per top-level statement and functions/subqueries > > use the same snapshot as that of top-level statement. > > Not so. SetQuerySnapshot is executed per querytree, not per top-level > statement --- for example, if a rule generates multiple queries from > a user statement, SetQuerySnapshot is called again for each query. > Is it possible that a rule generates multiple queries from a read(select)-only statement ? If so,the queries must be executed under the same snapshot in order to guaran tee read consistency from user's POV. As for non-select queries I'm not sure because read consistency doesn't have much meaning for them. I just remembered a report from Forest Wilkinson about a month ago [SQL] SQL functions not locking properly? Don't we have to distiguish simple procedure calls (select func();) and function calls as a part of a query ? As I mentioned once before,it seems a problem that arbitrary functions could be called from queries. As for procedures,it seems preferable that each statement of them is treated as a top-level query. Regards. Hiroshi Inoue