Can't Download Large CSVs

[aarontitus]

For example, it's now impossible to download all of the closed items for hurricane sandy-- the data set is just too big, and the server times out before the query can be completed.

I think we had settled on this approach to solve this issue: Use GAE's pagination feature to download a few hundred at a time into temporary csv files on the server. When the system reaches the end of line, combine the csv files into one download, then commence download.