[query] import_table: simplify code and improve speed #11782
Merged
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CHANGELOG:
hl.import_table
is up to twice as fast for small tables.The big change is optimizing for the single file, no filters case in which
we need not scan for the first extant row, that row must be in the first
partition, if it exists at all. Unfortunately there is no zero-RPC way to
determine the number of partitions in a table, so I must catch an error
about the lack of a zeroth partition.
I also did some refactoring:
hl.format
for constructing strings.should_filter_line
intoshould_remove_line
for clarity of name.should_remove_line
to use short-circuiting and/or instead of array folds.should_remove_line
to indicate (via returning None) when there are no filters enabled..collect()[0]
would beNone
if there were no values in the table. (It raises an error)hail.utils.deduplicate
(haha: I mean, there is already code for doing field dedupe)