Thanks John for your answer. The problem is how do I declare the cursor and fetch through C++ and libpq++? And if I fetch 1000 rows at a time, then how do I handle that when I reach the end and there are less than 1000 rows available? Or I need to fetch one row at a time like this http://stackoverflow.com/questions/16128142/how-to-use-pqxxstateless-cursor-class-from-libpqxx ?
A. 2014-05-04 12:11 GMT+03:00 John R Pierce <pie...@hogranch.com>: > On 5/4/2014 1:57 AM, alexandros_e wrote: > >> I have to execute an SQL query to Postgres by the following code. The >> query >> returns a huge number of rows (40M or more) and has 4 integer fields: >> When I >> use a workstation with 32Gb everything works but on a 16Gb workstation the >> query is very slow (due to swapping I guess). Is there any way to tell the >> C++ to load rows at batches, without waiting the entire dataset? With >> Java I >> never had these issues before, due to the probably better JDBC driver. >> > > see DECLARE and FETCH. > > http://www.postgresql.org/docs/current/static/sql-declare.html > http://www.postgresql.org/docs/current/static/sql-fetch.html > > > > > > -- > john r pierce 37N 122W > somewhere on the middle of the left coast > >
