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Initially posted as datamill-co#204.
This PR addresses the changes proposed in datamill-co#203
As described in the issue, loading data seemed unnecessarily slow. On a test CSV file containing 50k rows, each with 2 cols of fixed length text, target-postgres was spending about 20 seconds loading the data.
Some profiling helped identify the bottlenecks, as described in the issue.
This PR proposes 3 distinct improvements, in decreasing order of time savings (based on my test case). With cProfile instrumentation, the loading took approx 32 seconds instead of 20:
In the end, with these speedups applied, the same data now loads in under 4s instead of the original 20s.