Hi Tom, Appreciate so much for looking into this. This is a single database instance. I debugged a bit more after I posted the problem and realized that writer was actually working in asynchronous mode. Once I fixed that the program is working as expected. Thanks. sandeep On Sun, Aug 7, 2016 at 11:43 AM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > Sandeep Gupta <gupta.sandeep@xxxxxxxxx> writes: >> First program, lets say the writer, (using psql) appends to a table >> in the database. >> Second program, the reader, (python using alchemy) reads the data. >> This happens in loop, one for each day.The programs are fired in that order >> and the first program always commits after it inserts new rows. > >> The problem is that the second program does not see the updates of the first >> program consistently. > > There are only two possible explanations for that: > > 1. The writer isn't actually issuing a COMMIT when you think it is. > > 2. The reader is using a stale snapshot, ie it's using SERIALIZABLE > or REPEATABLE READ transaction mode and its transaction started before > the writer committed. > > If you're having trouble identifying the cause of the problem you > might try setting "log_statement = all" and looking at where BEGINs > and COMMITs get issued. > > (Well, I guess that only exhausts the possibilities as long as this is > happening on a single database server. If the reader is reading from > a hot-standby slave then replication delays might explain your problem. > But that would be a rather material omission of facts.) > > regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
