Give the merge copy parameter better documentation

[cpcloud]

See this SO question

The docstring should indicate what is not being copied unnecessarily (Indexes, ndarrays, etc.)

[jreback]

IIRC I think the copy parameter only matters here is its a trivial merge and you actually do want it copied (kind I like a reindex with the same index)

[cpcloud]

yep here's the explanation:

if the index join is the same as both indexes in the join it will return None for the indexers and when _JoinUnit.reindex_block is called copy will only take effect if the indexer is None which means what you said: trivial merge

[cpcloud]

still should say something about that....definitely not what i just wrote but something more informative than what's there

[moaraccounts]

take

[moaraccounts]

@jreback @cpcloud
I'm having trouble understanding how editing the merge copy parameter documentation resolves this. In the original SO question, OP is using concat, not merge.

It seems like the concat copy parameter needs adjustment, as running through the example from this indicates:

Note
It is worth noting that concat() (and therefore append()) makes a full copy of the data, and that constantly reusing this function can create a significant performance hit. If you need to use the operation over several datasets, use a list comprehension.

Maybe I'm missing something?

[jangorecki]

@moaraccounts Maybe this issue is just asking for a different thing than linked SO is about. I subscribed to this issue seeking better "merge" "copy" documentation, not a "concat" copy.

[TheMellyBee]

Can this be closed?