Consider query size cap or batch fetching for safety

[bluerogue251]

Currently there is no maximum size on the amount of data we could pull into memory at once. It's dependent on:

• What the user specifies as base query
• What the cardinality of children to parents is (for instance, if one parent row has 5 billion children rows, we might pull all 5 billion into memory at once)

There may be some way to give more safety around memory use. For instance, by putting a cap on rows fetched, by using jdbc batches for selects, etc.