Warning
This component will be available in the Palette of
Talend Studio on the condition that you have subscribed to one of
the Talend Platform products.
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Component family |
Data Quality |
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Function |
tReservoirSampling enables you to extract a |
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Purpose |
tReservoirSampling extracts a sample from the |
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Basic settings |
Schema and Edit schema |
A schema is a row description. It defines the number of fields to be processed and passed on Since version 5.6, both the Built-In mode and the Repository mode are Click Sync columns to retrieve the schema from |
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Built-In: You create and store the schema locally for this |
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Repository: You have already created the schema and |
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Sample Size |
Set how many rows to sample from the input flow. |
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Advanced settings |
Seed for random generator |
Set a random number if you want to extract the same sample in different Repeating the execution with a different value for the seed will result in a Keep this field empty if you want to extract a different data sample each time |
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tStat |
Select this check box to collect log data at the component |
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Usage |
This component helps you to test profiling analyses on a sample data and have tReservoirSampling can not |
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Limitation/prerequisite |
n/a |
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This scenario describes a basic Job that extracts sample data from an input flow.
Below is a capture of the input flow:
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Drop the following components from the Palette onto
the design workspace: tFileInputDelimited, tReservoirSampling and tFileOutputDelimited.
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Connect all the components together using the Row
> Main link.
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Double-click tFileInputDelimited to display the
Basic settings view and define the component
properties.
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In the File name/Stream field, browse to the file
to be used as the main input.This file provides some information about customers.
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Define the row and field separators and the header and footer in the corresponding
fields, if any. -
Click the […] button next to Edit schema to open a dialog box and define the input schema.
In this example, according to the input file structure, the schema is made of ten
columns.
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Click the [+] button and define the input columns
in the dialog box as in the above figure. Click OK to
close the dialog box. -
If needed, right-click tFileInputDelimited and
select Data Viewer to display a view of the input
data.
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Double-click tReservoirSampling to display the
Basic settings view and define the component
properties.
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Click the Edit schema button to view the input and
output columns and do any modifications in the output schema, if needed.
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In the Sample Size field, enter a number for the
rows you want to extract from the input flow, 24 in this example. -
Click the Advanced settings tab and enter a random
number in the Seed for random generator field.By setting a number in this field, you will extract the same sample in each
execution of the Job. Change the value if you want to extract a different sample.
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Double-click tFileOutputDelimited to display its
Basic settings view and define the component
properties.
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In the File Name field, specify the path to the
file to which you want to write the sample data. -
Define the row and field separators in the corresponding fields, if any.
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Save your Job and press F6 to execute it.
The sample data is extracted and written to the output file.
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Right-click the output component and select Data
Viewer to display the extracted data.
24 records have been extracted from the input file as you defined in the tReservoirSampling component settings. The Code column indicates that data has not been extracted
sequentially from the input file. Data has been extracted in a way that any profiling
results on the sample data will be close to the profiling results on the full data
set.