JuliaData / DataTables.jl / 450

85%

push

travis-ci

Specialize row_group_slots() and findrow() on column types to improve performance

Looping over columns is very slow when their type is unknown at compile time.
Specialize the method on the types of the key (grouping) columns by passing
a tuple of columns rather than a DataTable. This will force compiling a specific
method for each combination of key types, but their number should remain relatively low
and the one-time cost is worth it.

This dramatically improves performance of groupby(), but does not have a large
effect on join() since it is very inefficient in other areas.

Also add return type assertion for rowhash(). The fact that the type of
the columns isn't known at compile time appears to confuse inference,
which isn't able to detect that this function always returns UInt.
This reduces a lot the number of allocations when calling join(),
but doesn't really change performance.

27 of 27 new or added lines in 3 files covered. (100.0%)

1291 of 1514 relevant lines covered (85.27%)

8912.79 hits per line