Locating missing items in two sequences - 10,000 items

The problem is to detect values in source which are missing from target. These algorithms are both O(N)
A fuller set of algorithms.
Source Target Index Configuration

1. Setup test data

The test data is generated and saved to db

2. db: $target[value=$item]

Loop through source, lookup in target in indexed document in db

3. map

construct a map using the target and loop through the source