arrow

MINOR: [R] Simplify compare_dplyr_binding test helper (#14676)

A long time ago, dplyr expressions on Tables and RecordBatches were evaluated by calling compute functions on (Chunked)Arrays, calling Slice or Filter methods on the Tables/RBs, etc. So to make sure that all C++ bindings were exposed correctly, we needed to test that operations worked on both Tables and RecordBatches. 

Today, everything goes through ExecPlans, and RecordBatches get wrapped in Tables in creating TableSourceNodes: https://github.com/apache/arrow/blob/master/r/R/query-engine.R#L63. So as long as we are able to create a Table from a RecordBatch (tested elsewhere), the query evaluation is identical. This means we don't need to test every dplyr query twice.

On my machine, this cuts off a little more than 1/3 of the running time of the dplyr tests, or about 20 seconds. The bigger benefit IMO is that when there is a failure in one of these expectations, you'll only get it once instead of twice, so it will be less confusing to see what's up. 

Authored-by: Neal Richardson <neal.p.richardson@gmail.com>
Signed-off-by: Nic Crane <thisisnic@gmail.com>