Jesus Camacho Rodriguez created HIVE-11954:
----------------------------------------------
Summary: Extend logic to choose side table in MapJoin Conversion
algorithm
Key: HIVE-11954
URL: https://issues.apache.org/jira/browse/HIVE-11954
Project: Hive
Issue Type: Bug
Components: Physical Optimizer
Affects Versions: 2.0.0
Reporter: Jesus Camacho Rodriguez
Assignee: Jesus Camacho Rodriguez
Selection of side table (in memory/hash table) in MapJoin Conversion algorithm
needs to be more sophisticated.
In an N way Map Join, Hive should pick an input stream as side table (in memory
table) that has least cost in producing relation (like TS(FIL|Proj)*).
Cost based choice needs extended cost model; without return path its going to
be hard to do this.
For the time being we could employ a modified cost based algorithm for side
table selection.
New algorithm is described below:
1. Identify the candidate set of inputs for side table (in memory/hash table)
from the inputs (based on conditional task size)
2. For each of the input identify its cost, memory requirement. Cost is 1 for
each heavy weight relation op (Join, GB, PTF/Windowing, TF, etc.). Cost for an
input is the total no of heavy weight ops in its branch.
3. Order set from #1 on cost & memory req (ascending order)
4. Pick the first element from #3 as the side table.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
