bmerge could set a new flag when ans$starts is equal to seq_along
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Assessment
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- 4/5
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- 3-5 days
- Newbie friendliness
- 30/100
Research direction
Start by locating the bmerge entry point and tracing how ans$starts and ans$xo are produced. Check whether detecting the stated identical cases adds measurable overhead, then inspect downstream uses that subset data.table by ans$starts. Done means a returned flag accurately covers the requested cases without an unacceptable overhead or extra copy.
Written by the indexing model from the issue text.
Description
AFAIK adding that would impose an overhead in bmerge. In case if it wouldn't impose an overhead, then I think we should add it. @arunsrinivasan any idea on that?
Having such flag could be useful to avoid extra copy in downstream code, where we may need subset data.table by ans$starts. Note that it is not a common case, but rather an edge case, when we merge identical columns.
bmerge would need to return new flag which tells if
identical(ans$starts, seq_along(ans$starts))
eventually handling as well
identical(ans$xo[ans$starts], seq_along(ans$starts))
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