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| Problem with writing number of records in file |
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| Frik |
 Posted: Mon Nov 05, 2012 4:09 am Post subject: Problem with writing number of records in file |
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Acolyte
Joined: 25 Nov 2009
Posts: 69
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Hello,
I need to write csv file with:
1. Header (written once - first line in file)
2. Unknown numbers of records.
I'm doing it by reading a big file (couple of Mbs...),
reading it with FileInput Node with records options on, so I'm reading 1000 records every time (size of a records is 50, so it's configures to 50000).
It works realy well, but the problem is that in the header i have to write the number of the total records, which I don't know when I'm reading the file (because I read 1000 records).
Any fast and good solution?
is there a way to update the first record after i wrote it?
Thanks. |
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| ah.khalafallah |
| Posted: Sun Mar 03, 2013 3:15 am Post subject: |
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Newbie
Joined: 03 Mar 2013
Posts: 5
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Hi Frik,
as far as from what I understood,
it's only a one-file meaning it's one-time run
so you can set this field to the CARDINALITY function's output when you give it the Data Array in the Parsed Message.
but if it's done multiple runs, you need to read the last file you written and update the field by incrementing the value in the No. of Records in it with the number of records each time. |
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| Vitor |
| Posted: Sun Mar 03, 2013 5:22 am Post subject: |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| ah.khalafallah wrote: |
| so you can set this field to the CARDINALITY function's output when you give it the Data Array in the Parsed Message. |
If the file's being read 1000 records at a time then (as the OP pointed out) this will return 1000 not the true value. The question of if this is the best way to read a file like this is a separate topic....
| ah.khalafallah wrote: |
| but if it's done multiple runs, you need to read the last file you written and update the field by incrementing the value in the No. of Records in it with the number of records each time. |
The OP knows that; he's asking how you update a record already written.
_________________
Honesty is the best policy.
Insanity is the best defence. |
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| Vitor |
| Posted: Sun Mar 03, 2013 5:25 am Post subject: Re: Problem with writing number of records in file |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| Frik wrote: |
| is there a way to update the first record after i wrote it? |
Why does the header need to the first record you write out? Why not write it out when the last data record has been processed and use your favorite sort utility to move it to the top before the consuming application processes it?
_________________
Honesty is the best policy.
Insanity is the best defence. |
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