Scavenging the mail folder uncovered Randall F. Kern's letter:
Read committed is faster, but I have not done any tests to know how much faster. Read committed mode doesn't support concurrent updates either, but fails silently. In other words, given to concurrent queries:
update foo set a = a + 1 update foo set a = a + 2
Assuming these overlap, and a starting value of 0 for "a", read committed mode would result in "a" either being 1 or 2; serializable mode (with my patch) would result in "a" getting set to 3.
this is, imho, the Right Thing (TM), so psycopg will stay serializable. thank you again for the patch. federico -- Federico Di Gregorio MIXAD LIVE Chief of Research & Technology fog@mixadlive.com Debian GNU/Linux Developer & Italian Press Contact fog@debian.org God is real. Unless declared integer. -- Anonymous FORTRAN programmer