Buffer management issues (BUFFER_LOAD_FACTOR)

[lauritzthamsen]

ok, i only have a rough understanding of our buffer management, but on certain machine configurations AURA fails for buffer management related reasons.

how much of the main memory is reserved for buffers is currently defined relatively to the available memory.

when the BUFFER_LOAD_FACTOR is chosen very small (e.g. 1%), there might not be (m)any buffers on small machines, see https://travis-ci.org/lauritzthamsen/AURA/builds/29074045

may be it'd be wise to mix relative memory usage with specific limits such as a lower limit of buffers to reserve memory for (MIN_BUFFER_COUNT). does that make sense?

when the BUFFER_LOAD_FACTOR is however set to be a bigger chuck (e.g. 40%), the system currently can run out of memory, see https://travis-ci.org/lauritzthamsen/AURA/builds/29075554

that shouldn't happen in any case, right? at least the system should tell the user on startup that there isn't enough memory for AURA / the query (yet, not with a fixed 1 GB requirement i'd say).