Hi, On 2021-05-05 18:33:27 +0800, Craig Ringer wrote: > I'm thinking of piggy-backing on the approach used in the "Get memory > contexts of an arbitrary backend process" patch in order to provide access > to detailed reorder buffer content statistics from walsenders on request. > > Right now the reorder buffer is mostly a black-box. I mostly rely on gdb or > on dynamic probes (perf, systemtap) to see what it's doing. I intend a > patch soon to add a couple of fields to struct WalSnd to report some very > coarse reorder buffer stats - at least oldest buffered xid, number of > buffered txns, total bytes of buffered txns in memory, total bytes of > buffered txns spilled to disk. > > But sometimes what I really want is details on the txns that're in the > reorder buffer, and that's not feasible to export via always-enabled > reporting like struct WalSnd. So I'm thinking that the same approach used > for the memory context stats patch might work well for asking the walsender > for a detailed dump of reorder buffer contents. Something like a > per-buffered-txn table of txn topxid, start-lsn, most recent change lsn, > number of changes, number of subxids, number of invalidations, number of > catalog changes, buffer size in memory, buffer size spilled to disk. > > Anyone drastically opposed to the idea?
I am doubtful. The likelihood of ending with effectively unused code seems very substantial here. Greetings, Andres Freund
