Yeb Havinga: > fkater@xxxxxxxxxxxxxx wrote: [...] > > We have done a test with two connections to the database > > on different computers. After the first client (writer) > > had inserted new data into a quite simple table, it told > > another client (by TCP communication) to be ready, > > however, this second client (reader) did not see the > > data then immediately in the database. So we delayed the > > reading client from 2 to 5s to have it see all data in > > the table. > Essential information is missing. Did the first client > COMMIT before toggling client 2? Yes, of course, the commit was done before toggling client 2. I would like to mention that the table itself is simple however contains a bytea column and some of the inserted rows contain some MBs of binary data which usually take a while. But, yes, we trigger client 2 only *after* the commit was done and returned successfully (using v8.2.4 on win32 via libpq). > Also you might find the information from > http://developer.postgresql.org/pgdocs/postgres/transaction-iso.html > interesting, since that specifies how to control behaviour > of concurrent transactions looking at each others data. Thank you for the interesting link. I think, though, that this does not address the question why there is a delay between the point in time A that client 1 has successfully commited and the point in time B when client 2 can see all new rows! Even in pure serialization it should be possible that client 2 can immediately start reading *after* client 1 has completely commited, shouldn't it? FYI: We are using the default setup for transaction isolation. > > Secondly: If yes, is there a way to determine when newly > > inserted data is visible to other clients? > > > Not before it is committed. To which clients the just > committed data is visible depends on the transaction > isolation level (see link above). Hm, I do not get it -- AFAIK the article you mentioned deals with the question what a concurrent transaction can see from another one which is pending/not committed. But this is not the case here. The first transaction is commited before. To sum up our question: If client 1 has commited some rows, when is the moment that client 2 can see/read all that data? Do we have to consider a gap and if yes how to determine it? Thank You! Felix -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
