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https://issues.apache.org/jira/browse/PIG-2600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13231360#comment-13231360
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Prashant Kommireddi commented on PIG-2600:
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INVERSEMAP is a nice to have functionality, not necessarily uber-useful. This
could be similar to
http://google-collections.googlecode.com/svn/trunk/javadoc/com/google/common/collect/BiMap.html
except the fact that it does not require the restriction that values are
unique. Rather we could think of a strategy to determine which value->key pairs
the function returns
1. First occurring pair, key pair -> (v1, k1) from (k1,v1)(k2,v1)
2. Last occurring pair -> (v1, k2) from (k1,v1)(k2,v1)
3. All keys corresponding to value -> (v1, (k1,k2))
Input could be tuple of maps or bag of maps.
INVERSEMAP has been useful in a few situations to me, for eg to get
field->index map from index->field. I see it being useful in few cases with
click-through analysis as well.
Again, not a super required use-case but good to have.
> Better Map support
> ------------------
>
> Key: PIG-2600
> URL: https://issues.apache.org/jira/browse/PIG-2600
> Project: Pig
> Issue Type: Improvement
> Reporter: Jonathan Coveney
> Fix For: 0.11
>
>
> It would be nice if Pig played better with Maps. To that end, I'd like to add
> a lot of utility around Maps.
> - TOBAG should take a Map and output {(key, value)}
> - TOMAP should take a Bag in that same form and make a map.
> - KEYSET should return the set of keys.
> - VALUESET should return the set of values.
> - VALUELIST should return the List of values (no deduping).
> - INVERSEMAP would return a Map of values => the set of keys that refer to
> that Key
> This would all be pretty easy. A more substantial piece of work would be to
> make Pig support non-String keys (this is especially an issue since UDFs and
> whatnot probably assume that they are all Integers). Not sure if it is worth
> it.
> I'd love to hear other things that would be useful for people!
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