PERF: Index.__getitem__ should not need to do dtype inference

[jorisvandenbossche]

Currently, the __getitem__ call in a snippet like

idx = pd.Index([1, 2, 3, 4])
idx[np.array([0, 3])]

does type inference when creating the new Index object (using _shallow_copy_with_infer), while I think we can always know for sure the result will be another Int64Index (for the above example) ?

[jbrockmendel]

Index.__getitem__ no longer uses _shallow_copy_with_infer. Are there other optimizations you had in mind?

[jbrockmendel]

Closing as I'm pretty sure this no longer does type inference. Feel free to reopen if ive got this wrong.

[jorisvandenbossche]

Yep, that's correct