* Tom Lane (tgl@xxxxxxxxxxxxx) wrote: > Tatsuo Ishii <ishii@xxxxxxxxxxxxxx> writes: > > Shall I commit to master and all supported branches? > > I'm not excited by this patch. It dodges the O(N^2) lock behavior for > the initial phase of acquiring the locks, but it does nothing for the > lock-related slowdown occurring in all pg_dump's subsequent commands. > I think we really need to get in the server-side fix that Jeff Janes is > working on, and then re-measure to see if something like this is still > worth the trouble. I am also a tad concerned about whether we might not > have problems with parsing memory usage, or some such, with thousands of > tables being listed in a single command. I can't imagine a case where it's actually better to incur the latency penalty (which is apparently on the order of *minutes* of additional time here..) than to worry about the potential memory usage of having to parse such a command. If that's really a concern, where is that threshold, and could we simply cap pg_dump's operations based on it? Is 1000 alright? Doing a 'lock' w/ 1000 tables at a time is still going to be hugely better than doing them individually and the amount of gain between every-1000 and all-at-once is likely to be pretty minimal anyway... The current situation where the client-to-server latency accounts for multiple minutes of time is just ridiculous, however, so I feel we need some form of this patch, even if the server side is magically made much faster. The constant back-and-forth isn't cheap. Thanks, Stephen
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