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Kevin Grittner wrote: >> I think most people have always assumed that >> BEGIN starts the transaction and that is the point at >> which the snapshot is obtained. > But there is so much evidence to the contrary. Not only does the > *name* of the command (BEGIN or START) imply a start, but > pg_stat_activity shows the connection "idle in transaction" after > the command (and before a snapshot is acquired) Er...I think we are arguing the same thing here. So no contrary needed? :) > Why? This "fix" might not deal with the bigger issues that I > discussed, like that the later-to-start and > later-to-acquire-a-snapshot transaction might logically be first in > the apparent order of execution. You can't "fix" that without a > lot of blocking -- that most of us don't want. Right, which is why the suggestion of a user-controllable switch, that defaults to the current behavior, seems an excellent compromise. > Depending on *why* they think this is important, they might need to > be acquiring various locks to prevent behavior they don't want, in which case > having acquired a snapshot at BEGIN would be exactly the *wrong* > thing to do. The exact nature of the problem we're trying to solve > here does matter. I cannot speak to the OP, but I also do not think we should try and figure out every possible scenario people may have. Certainly the long-standing documentation bug may have caused some unexpected or unwanted behavior, so let's start by fixing that. Tom Lane wrote: > Another thing that I think hasn't been mentioned in this thread is > that we used to have severe problems with client libraries that like > to issue BEGIN and then go idle until they have something to do. > Which, for some reason, is a prevalent behavior. I'm not advocating changing the default behavior, but I would not want to see bad client libraries used a reason for any change we make. Clients should not be doing this, period, and there is no reason for us to support that. - -- Greg Sabino Mullane g...@turnstep.com End Point Corporation http://www.endpoint.com/ PGP Key: 0x14964AC8 201411071600 http://biglumber.com/x/web?pk=2529DF6AB8F79407E94445B4BC9B906714964AC8 -----BEGIN PGP SIGNATURE----- iEYEAREDAAYFAlRdMwwACgkQvJuQZxSWSsh/mgCeMdrj15bNVtzBhecG+QT2SlKh jboAnAjctUcrlA2aCCQmIsSM87ulmFEn =U5ld -----END PGP SIGNATURE----- -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
