On 30 October 2017 at 17:25, Ivan Kartyshov <i.kartys...@postgrespro.ru> wrote:
> It sounds reasonable. I can offer the following version. > > WAIT LSN lsn_number; > WAIT LSN lsn_number TIMEOUT delay; > WAIT LSN lsn_number INFINITE; > WAIT LSN lsn_number NOWAIT; > > > WAIT [token] wait_value [option]; > > token - [LSN, TIME | TIMESTAMP | CSN | XID] > option - [TIMEOUT | INFINITE | NOWAIT] > > Ready to listen to your suggestions. OK, on review we want this feature in PG11 Many people think we will want to wait on a variety of things in the future. Support for those things can come in the future when/if they exist. In PG11, I propose the following command, sticking mostly to Ants' syntax, and allowing to wait for multiple events before it returns. It doesn't hold snapshot and will not get cancelled by Hot Standby. WAIT FOR event [, event ...] options event is LSN value TIMESTAMP value options TIMEOUT delay UNTIL TIMESTAMP timestamp (we have both, so people don't need to do math, they can use whichever they have) We do not need "INFINITE" or "INFINITELY", obviously the default mode for WAIT is to continue waiting until the thing you asked for happens. I couldn't see the point of the NOWAIT option, was that a Zen joke? WAIT can be issued on masters as well as standbys, no need to block that. If you want this in PG11, please work on this now, including docs and tap tests. Please submit before 1 March and I will shepherd this to commit. Thomas, I suggest we also do what Robert suggested elsewhere which was to have an connection option that returns xid or lsn (or both) via the protocol, so we can use that with the WAIT command and you can have the overall causal consistency feature into PG11. I'll be reviewer for that feature also if you submit. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
