Yes Sent from my iPhone
On Dec 23, 2010, at 8:02 PM, "bharath vissapragada" <bharathvissapragada1...@gmail.com > wrote: > 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 <nj...@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" >> <bharathvissapragada1...@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 >> >>
