- define `datetime`, `printf` fns in pg so it produces similar
output as sqlite
- tidy up input data to be less wide
To do: some fns to make it easy to generate a new test case. Probably
want to mount all the 3 parquets simultaneously and refer to the
sqlite table by the same name as the pg table.
- "fixed_size_binary" -> "binary_10"
- make null parquet use rowgroups of sie 10: first rowgroup
has no nulls, 2nd has all null, 3rd-10th have alternating
nulls
This is prep for making a Postgres layer to use as an oracle
for generating test cases so that we have good coverage before
implementing advanced `xBestIndex` and `xFilter` modes.
