Thanks Jonathan for looking into it and for your suggestions.
The reason why I came with a clause rather than a separate operator was to
avoid adding additional operators to the grammar.
So adding ROLLUP, GROUPING_SET will need separate logical operators adding to
the complexity. I am planning to keep everything under cube operator, so only
LOCube and POCube operators will be added additionally. And as you and Dmitriy
have mentioned the purpose of HAVING clause is the same as FILTER so we do not
need a separate HAVING clause.
I will give a quick recap of cube related operations and multiple syntax
options for achieving the same. I am also adding partial cubing and rollup in
this discussion.
1) CUBE
Current syntax:
alias = CUBE rel BY (a, b);
Following group-by's will be computed:
(a, b)
(a)
(b)
()
2) Partial CUBE
Proposed syntax:
alias = CUBE rel BY a, (b, c);
Following group-by's will be computed:
(a, b, c)
(a, b)
(a, c)
(a)
3) ROLLUP
Proposed syntax 1:
alias = CUBE rel BY ROLLUP(a, b);
Proposed syntax 2:
alias = CUBE rel BY (a::b);
Proposed syntax 3:
alias = ROLLUP rel BY (a, b);
Following group-by's will be computed:
(a, b)
(a)
()
4) Partial ROLLUP
Proposed syntax 1:
alias = CUBE rel BY a, ROLLUP(b, c);
Proposed syntax 2:
alias = CUBE rel BY (a, b::c);
Proposed syntax 3:
alias = ROLLUP rel BY a, (b, c);
Following group-by's will be computed:
(a, b, c)
(a, b)
(a)
5) GROUPING SETS
Proposed syntax 1:
alias = CUBE rel BY GROUPING SETS((a), (b, c), (c))
Proposed syntax 2:
alias = CUBE rel BY {(a), (b, c), (c)}
Proposed syntax 3:
alias = GROUPING_SET rel BY ((a), (b, c), (c))
Following group-by's will be computed:
(a)
(b, c)
(c)
Please vote for syntax 1, 2 or 3 so that we can come to a consensus before I
start hacking the grammar file.
Thanks
-- Prasanth
On May 29, 2012, at 4:05 PM, Jonathan Coveney wrote:
> Hey Prashanth, happy hacking.
>
> My opinion:
>
> CUBE:
>
> alias = CUBE rel BY (a,b,c);
>
>
> I like that syntax. It's unambiguous what is going on.
>
>
> ROLLUP:
>
>
> alias = CUBE rel BY ROLLUP(a,b,c);
>
>
> I never liked that syntax in SQL. I suggest we just do what we did with CUBE.
> IE
>
>
> alias = ROLLUP rel BY (a,b,c);
>
>
> GROUPING SETS:
>
>
> alias = CUBE rel BY GROUPING SETS((a,b),(b),());
>
>
> I don't like this. The cube vs. grouping sets is confusing to me. maybe
> following the
> same pattern you could do something like:
>
> alias = GROUPING_SET rel BY ((a,b),(b),());
>
> As far as having, is there an optimization that can be done with a HAVING
> clause that can't be done based on the logical plan that comes afterwards?
> That seems odd to me. Since you have to materialize the result anyway,
> can't the having clause just be a FILTER that comes after the cube? I don't
> know why we need a special syntax.
>
> My opinion. Forgive janky formatting, gmail + paste = pain.
> Jon
>
> 2012/5/27 Prasanth J <[email protected]>
>
>> Hello everyone
>>
>> I am looking for feedback from the community about the syntax for
>> CUBE/ROLLUP/GROUPING SETS operations in pig.
>> I am moving the discussion from JIRA to dev-list so that everyone can
>> share their opinion for operator syntax. Please have a look at the syntax
>> proposal at the link below and let me know your opinion
>>
>>
>> https://issues.apache.org/jira/browse/PIG-2167?focusedCommentId=13277644&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13277644
>>
>> Thanks
>> -- Prasanth
>>
>>
