On Thu, 25 Jul 2019 at 05:49, Tom Lane <t...@sss.pgh.pa.us> wrote: > On the whole, I don't especially like this approach, because of the > confusion between peak lock count and end-of-xact lock count. That > seems way too likely to cause problems.
Thanks for having a look at this. I've not addressed the points you've mentioned due to what you mention above. The only way I can think of so far to resolve that would be to add something to track peak lock usage. The best I can think of to do that, short of adding something to dynahash.c is to check how many locks are held each time we obtain a lock, then if that count is higher than the previous time we checked, then update the maximum locks held, (probably a global variable). That seems pretty horrible to me and adds overhead each time we obtain a lock, which is a pretty performance-critical path. I've not tested what Andres mentioned about simplehash instead of dynahash yet. I did a quick scan of simplehash and it looked like SH_START_ITERATE would suffer the same problems as dynahash's hash_seq_search(), albeit, perhaps with some more efficient memory lookups. i.e it still has to skip over empty buckets, which might be costly in a bloated table. For now, I'm out of ideas. If anyone else feels like suggesting something of picking this up, feel free. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
