> > I'm wondering if we could detect a funcion has a side effect, > > i.e. does a write to database. This is neccessary for pgpool to decide > > if a qeury should to be sent to all of databases or not. If a query > > includes functions which do writes to database, it should send the > > query to all of databases, otherwise the contents of databases go into > > inconsistent state. > > > > Currently we have three properties of functions: IMMUTABLE, STABLE and > > VOLATILE. According to docs IMMUTABLE or STABLE functions do not write > > to database. VOLATILE functions *may* do writes to database. Maybe I > > could regard VOLATILE functions always do write, but priblem is, > > VOLATILE qfunctions such as random() and timeofday() apparently do not > > write and sending those queries that include such functions is > > overkill. > > > > Can we VOLATILE property divide into two categories, say, VOLATILE > > without write, and VOLATILE with write? > > pgpool parses the query before deciding how to route it, yes?
Right. > Why not mark random() and timeofday() as stable in the pgpool catalog, > yet leave them as volatile on the database servers? It will "just work" > then. Please note that random() and timeofday() are just examples. What I'm thinking about was, a function which directly or indirectly cause write to database (thus lead writing to log). Consider a function that calls those has-side-effect functions. We need a property which is inherited to child function to parent function. -- Tatsuo Ishii SRA OSS, Inc. Japan English: http://www.sraoss.co.jp/index_en.php Japanese: http://www.sraoss.co.jp -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
