Inner join using an inequality expression

Question

Background

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Rolling join on data.table with duplicate keys

Odd behaviour w

Answer 1

Here's the unclever approach: take the cross/Cartesian join, and then filter.

merge(dt_arrive, dt_depart, allow.cartesian=TRUE)[arrival_minutes.y > arrival_minutes.x]

#    txn_id   place arrival_minutes.x journey_id.x arrival_minutes.y journey_id.y
# 1:      1 place_a               515            1               519           12
# 2:      1 place_a               515            1               543           13
# 3:      1 place_a               534            2               543           13

By taking the Cartesian join, we're liable to eat up a lot of memory.