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From bharath vissapragada <bharathvissapragada1...@gmail.com>
Subject Re: mergeJoinTree ??
Date Fri, 24 Dec 2010 04:01:26 GMT
Hi,

Thanks for the reply .

This is the optimization of converting 2 MR jobs to a single MR job
right ? as we are using only a single join val per table.

Thanks
Bharath.V
4th year undergraduate,
IIIT Hyderabad,

On Fri, Dec 24, 2010 at 12:22 AM, Namit Jain <njain@fb.com> wrote:
> The idea there is to merge the join trees.
>
> For eg. If the query is:
>
> Select * from
> T1 join T2 on T1.key = T2.key
> join T3 on T1.key = T3.key
> Where ...
>
>
> One join can have 3 inputs: T1, T2 and T3.
>
> mergeJoinTree() merges the 2 join operators (T1,T2) and (result of
> (T1,T2), T3)
> into a new join operator with 3 children (T1,T2,T3)
>
>
> On 12/23/10 4:24 AM, "bharath vissapragada"
> <bharathvissapragada1990@gmail.com> wrote:
>
>>Hi all,
>>
>>
>>Once the JoinTrees are created by the the semantic analyzer for a
>>query block , a function mergeJoinTree(qb) is called .
>>Can anyone tell me what it does ?
>>
>>Thanks in anticipation,
>>Bharath.V
>
>

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