several Gb is about 1GB, that's not too much. In case you meant 'several GB', that shouldn't be a problem as well.
The first thing I'd do would be creating an index on the column used for dividing the data. Then I'd just use the command COPY with a proper select to save the data to a file.
If each select lasts for several hours, make the select faster. Good index usually helps. You can also post here the query which lasts for too long, and attach its plan as well.
I've been looking for a way to write a table into multiple files, and am wondering if there are some clever suggestions. Say we have a table that is too large (several Gb) to write to a file that can be used for further analyses in other languages. The table consists of a timestamp field and several numeric fields, with records every 10th of a second. It could be meaningfully broken down into subsets of say 20 minutes worth of records. One option is to write a shell script that loops through the timestamp, selects the corresponding subset of the table, and writes it as a unique file. However, this would be extremely slow because each select takes several hours, and there can be hundreds of subsets. Is there a better way?
