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Hashed File - Key column
Posted: Thu Jan 29, 2009 1:06 am
by DEEPTI
Hi all,
Is it necessary that we have to select the key column in the ouput tab of a hashed file which was defined in the input tab?
Let me say I have three columns in the input tab of a hashed file
A- Key column ,
B
and
C
My problem is when I am not selecting the column A from the input side,
the value of first column in the output tab(whther it is B or C) is becoming equal to the value specified in the column A in the input tab.
Thanks in Advance,
Deepti
Re: Hashed File - Key column
Posted: Thu Jan 29, 2009 1:10 am
by swarnkar
It's necessary to have key column to be included in hashed file.
- Nitin
Re: Hashed File - Key column
Posted: Thu Jan 29, 2009 1:11 am
by swarnkar
It's necessary to have key column to be included in hashed file.
- Nitin
Posted: Thu Jan 29, 2009 1:26 am
by hemanthakumar
Hi,
its not necessary that we have to select the key column in the ouput tab of a hashed file which was defined in the input tab? But It's necessary to have any key column .
Posted: Thu Jan 29, 2009 1:27 am
by hemanthakumar
Hi,
its not necessary that we have to select the key column in the ouput tab of a hashed file which was defined in the input tab? But It's necessary to have any key column .
Re: Hashed File - Key column
Posted: Thu Jan 29, 2009 1:27 am
by DEEPTI
Thanks Nitin.
Is it necessary that the output columns should be in the same order like the input columns in the hash file?
Also In order to remove that key column, do I need to include another transformer.
Regards,
Deepti
Posted: Thu Jan 29, 2009 1:47 am
by ray.wurlod
I'm confused here. A hashed file MUST have at least one key column. In the Transformer stage you set up a key expression that generates a value that is looked up.
Order of key columns in the hashed file is vital. Order of non-key columns is not, provided that the metadata have been handled rigorously. But it's probably better to preserve the storage order of columns, because this will lead to more efficient extraction.
Re: Hashed File - Key column
Posted: Thu Jan 29, 2009 1:51 am
by swarnkar
DEEPTI wrote:Thanks Nitin.
Is it necessary that the output columns should be in the same order like the input columns in the hash file?
Also In order to remove that key column, do I need to include another transformer.
Regards,
Deepti
Deepti,
If you want to reorder the columns then you have to maintain their position in the"Postion" grid of "Column" tab. Just mentioned the column position as in the file while creating it.
And as per my understanding of hashed file, One woun't be able to read data properly if the key columns differs while reading as against while writing the hashed file.
I request to DS Gurus to clear/confirm my understanding hashed file.
Regards,
Nitin Swarnkar.