bump csv field size limit in load_csv so long rows parse#50
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The csv module's underlying C parser caps each field at 131072 bytes by default. load_csv had no protection against that, so a row with a long string (e.g. a nucleotide sequence, a large JSON blob, an embedded log line) raised an uncaught _csv.Error instead of being returned to the caller. Set csv.field_size_limit(sys.maxsize) at the top of load_csv so the parser is allowed to handle the longest field the caller can possibly give it. sys.maxsize is the platform's PY_SSIZE_T_MAX and matches the recommendation in the Python csv docs for "set the limit as high as possible" without overflowing the parser. Closes simonw#41.
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Closes #41.
The csv module's C parser caps each field at 131072 bytes by default.
`load_csv` had no protection against that, so a row with a long string
(e.g. a nucleotide sequence, a large JSON blob, an embedded log line)
raised an uncaught `_csv.Error: field larger than field limit (131072)`
instead of being returned to the caller.
Set `csv.field_size_limit(sys.maxsize)` at the top of `load_csv` so the
parser is allowed to handle the longest field the caller can possibly
give it. `sys.maxsize` is the platform's `PY_SSIZE_T_MAX` and matches
the recommendation in the Python csv docs
for "set the limit as high as possible" without overflowing the parser.
Tests: `tests/test_csv_diff.py` now has `test_load_csv_handles_fields_larger_than_default_limit`
(200_000-byte field) and `test_load_csv_handles_tsv_with_long_fields` (same
size, tab-separated). Both fail on master with the original `_csv.Error`
and pass with the bump. The full `tests/` suite still passes 26/26.