Comment 3 for bug 1847805

I've updated the above-linked branch to avoid using cursors when we know we're only going to retrieve one row. This should reduce any measurable, new overhead.

From the first commit message, in case it will produce some interest:

Because we check authz for rows retrieved by open-ils.pcrud calls after the underlying query is executed, including any limit/offset-based paging, we can fail to return results when the first "page" is full of rows that the calling user cannot see.

With this commit, we switch to SQL cursors and page through results in the application logic, which guarantees that the situation above will not impact legitimate row visibility.

More generally, this will should improve memory use by pcrud (along with cstore and other similar services) by avoiding initial full retrieval of results. Only those that are needed for the final result will consume memory for the full lifetime of the request.

Additionally, this may prove to increase speed of some queries, especially because Postgres has the option to optimize for "fast-start" plans.