Jaime Casanova írta: > On Mon, Mar 1, 2010 at 2:56 PM, Peter Eisentraut <pete...@gmx.net> wrote: > >> On tis, 2010-02-23 at 16:54 -0500, Jaime Casanova wrote: >> >>> On Tue, Feb 23, 2010 at 2:02 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >>> >>>> There may be some value in inventing a "has no side effects" marker, but >>>> that should not be confused with IMMUTABLE/STABLE. >>>> >>>> >>> a READONLY function? >>> >> SQL standard: >> >> <SQL-data access indication> ::= >> NO SQL >> | CONTAINS SQL >> | READS SQL DATA >> | MODIFIES SQL DATA >> >> > > good! > > >> Notice also that this is separate from >> >> <deterministic characteristic> ::= >> DETERMINISTIC >> | NOT DETERMINISTIC >> >> > > so IMMUTABLE = DETERMINISTIC NO SQL, > STABLE = DETERMINISTIC READS SQL DATA > VOLATILE = NOT DETERMINISTIC MODIFIES SQL DATA > > >> which is the SQL standard's variant of volatility. >> >> So someone has already had the idea that these two should exist >> separately. >> >> > > seems something we should implement >
At least the combinations to recognize the current IMMUTABLE/STABLE/VOLATILE features. By definition, READS SQL DATA and MODIFIES SQL DATA cannot be DETERMINISTIC. But I can imagine some C and PL/Perl functions that are NOT DETERMINISTIC NO SQL. And what does "CONTAINS SQL" mean? Is it distinct from the other two READS/MODIFIES SQL DATA markers? "SELECT CURRENT_TIMESTAMP" may be an example but it doesn't seem to be significantly different from $$SELECT $1 || $2;$$ LANGUAGE SQL or the same written in PL/Perl or C. Best regards, Zoltán Böszörményi -- Bible has answers for everything. Proof: "But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil." (Matthew 5:37) - basics of digital technology. "May your kingdom come" - superficial description of plate tectonics ---------------------------------- Zoltán Böszörményi Cybertec Schönig & Schönig GmbH http://www.postgresql.at/ -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
