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How to decide which partition to be used in what kind of job
Posted: Tue May 11, 2010 4:21 am
by taral
We have different type of partition ie.
Hash Partition
Entire Prtition
Round robin
Same.
How can we decide which partition has to be used?
Posted: Tue May 11, 2010 4:44 am
by srinivas.g
By default it is Auto.
join,merge ---> hash
lookup-->entire
Posted: Tue May 11, 2010 6:16 am
by chulett
Lookup-->Entire as a blanket statement? Yikes. To the OP - practice, experience and experimentation help.
Posted: Tue May 11, 2010 8:46 am
by nagarjuna
It depends on type of req you are having .But decide whether its a keyed partitioning or non-key then as mentioned by craig experiment and decide .
Posted: Tue May 11, 2010 5:03 pm
by ray.wurlod
Welcome aboard.
There are actually eight choices for partitioning algorithm, and four for collecting. However, the decision is usually easier than that.
If you don't need to keep like-valued keys together, use an algorithm that spreads rows as evenly as possible over processing nodes. If you do need to keep like-valued keys together, use a key-based algorithm (modulus for a single integer key, hash otherwise). Range partitioning is rarely used, and requires that you pre-process your data to generate a "range map". Entire for reference input to Lookup stage is handy in that it guarantees that all valid lookups will succeed, but comes at a cost on cluster/grid environments in that all records have to be sent to all nodes (in an SMP environment one copy is lodged in shared memory).