I have one query regarding Lookup Stage.
In the previous post of this forum some body had mentioned the lookup as in-memory lookups .
So I want to know, how many types of lookup present in Lookup Stage, and how do they differe in implemention, in result as well as in performance too.
Thanks & regards,
Sid
Query regarding Lookup Stage
Moderators: chulett, rschirm, roy
Re: Query regarding Lookup Stage
There is only one 'type' of Lookup in a Lookup Stage, but its the implementation of conditional lookups, or handling of data when lookup conditions are not met that will result in variation of the output. I am sure, thesid19 wrote:I have one query regarding Lookup Stage.
In the previous post of this forum some body had mentioned the lookup as in-memory lookups .
So I want to know, how many types of lookup present in Lookup Stage, and how do they differe in implemention, in result as well as in performance too.
Thanks & regards,
Sid
manual that comes along with the installation will be sufficient to answer all those questions.
Performance varies with the hardware, row volume,etc.
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Most lookups performed by a Lookup stage are "in-memory" lookups, in that the reference table is pre-loaded into a virtual Data Set.
This is manifested as a composite operator consisting of LUT_CreateOp and LUT_ProcessOp operators; the first loads the table, the second uses it to perform lookups. You can see these in the job score.
The only exception is a so-called "sparse lookup", in which the lookup is performed directly against a database table. Sparse lookup is only supported via DB2 and Oracle Enterprise stages.
This is manifested as a composite operator consisting of LUT_CreateOp and LUT_ProcessOp operators; the first loads the table, the second uses it to perform lookups. You can see these in the job score.
The only exception is a so-called "sparse lookup", in which the lookup is performed directly against a database table. Sparse lookup is only supported via DB2 and Oracle Enterprise stages.
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Any contribution to this forum is my own opinion and does not necessarily reflect any position that IBM may hold.
Any contribution to this forum is my own opinion and does not necessarily reflect any position that IBM may hold.