tFuzzyMatch

tFuzzyMatch properties

Component family	Data Quality
Function	Compares a column from the main flow with a reference column from the lookup flow and outputs the main flow data displaying the distance
Purpose	Helps ensuring the data quality of any source data against a reference data source.
Basic settings	Schema and Edit schema	A schema is a row description, it defines the number of fields to be processed and passed on to the next component. The schema is either Built-in or stored remotely in the Repository. Since version 5.6, both the Built-In mode and the Repository mode are available in any of the Talend solutions. Two read-only columns, Value and Match are added to the output schema automatically.
		Built-in: The schema will be created and stored locally for this component only. Related topic: see Talend Studio User Guide.
		Repository: The schema already exists and is stored in the Repository, hence can be reused in various projects and job designs. Related topic: see Talend Studio User Guide.
	Matching type	Select the relevant matching algorithm among: Levenshtein: Based on the edit distance theory. It calculates the number of insertion, deletion or substitution required for an entry to match the reference entry. Metaphone: Based on a phonetic algorithm for indexing entries by their pronunciation. It first loads the phonetics of all entries of the lookup reference and checks all entries of the main flow against the entries of the reference flow. Double Metaphone: a new version of the Metaphone phonetic algorithm, that produces more accurate results than the original algorithm. It can return both a primary and a secondary code for a string. This accounts for some ambiguous cases as well as for multiple variants of surnames with common ancestry.
	Min distance	(Levenshtein only) Set the minimum number of changes allowed to match the reference. If set to 0, only perfect matches are returned.
	Max distance	(Levenshtein only) Set the maximum number of changes allowed to match the reference.
	Matching column	Select the column of the main flow that needs to be checked against the reference (lookup) key column
	Unique matching	Select this check box if you want to get the best match possible, in case several matches are available.
	Matching item separator	In case several matches are available, all of them are displayed unless the unique match box is selected. Define the delimiter between all matches.
Global Variables	NB_LINE: the number of rows read by an input component or transferred to an output component. This is an After variable and it returns an integer. ERROR_MESSAGE: the error message generated by the component when an error occurs. This is an After variable and it returns a string. This variable functions only if the Die on error check box is cleared, if the component has this check box. A Flow variable functions during the execution of a component while an After variable functions after the execution of the component. To fill up a field or expression with a variable, press Ctrl + Space to access the variable list and choose the variable to use from it. For further information about variables, see Talend Studio User Guide.
Usage	This component is not startable (green background) and it requires two input components and an output component.
Log4j	The activity of this component can be logged using the log4j feature. For more information on this feature, see Talend Studio User Guide. For more information on the log4j logging levels, see the Apache documentation at http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/Level.html.

Scenario 1: Levenshtein distance of 0 in first names

This scenario describes a four-component Job aiming at checking the edit distance
between the First Name column of an input file with the data of the
reference input file. The output of this Levenshtein type check is displayed along with
the content of the main flow on a table

Setting up the Job

Drag and drop the following components from the Palette to the design workspace: tFileInputDelimited (x2), tFuzzyMatch, tLogRow.
Link the first tFileInputDelimited
component to the tFuzzyMatch component
using a Row > Main connection.
Link the second tFileInputDelimited
component to the tFuzzyMatch using a
Row > Main connection (which appears as a Lookup row on the design workspace).
Link the tFuzzyMatch component to the
standard output tLogRow using a Row > Main
connection.

Configuring the components

Define the first tFileInputDelimited in
its Basic settings view. Browse the system
to the input file to be analyzed.
Define the schema of the component. In this example, the input schema has
two columns, firstname and gender.
Define the second tFileInputDelimited
component the same way.

Warning

Make sure the reference column is set as key column in the
schema of the lookup flow.
Double-click the tFuzzyMatch component to
open its Basic settings view, and check its
schema.

The Schema should match the Main input flow schema in order for the main flow
to be checked against the reference.

Note that two columns, Value and
Matching, are added to the output
schema. These are standard matching information and are read-only.
Select the method to be used to check the incoming data. In this scenario,
Levenshtein is the Matching
type to be used.
Then set the distance. In this method, the distance is the number of char
changes (insertion, deletion or substitution) that needs to be carried out
in order for the entry to fully match the reference.

In this use case, we set both the minimum distance and the maximum
distance to 0. This means only the exact
matches will be output.
Also, clear the Case sensitive check
box.
Check that the matching column and look up column are correctly
selected.
Leave the other parameters as default.

Executing the Job

Save the Job and press F6 to execute the
Job.

As the edit distance has been set to 0 (min and max), the output shows the result
of a regular join between the main flow and the lookup (reference) flow, hence only
full matches with Value of 0 are displayed.

A more obvious example is with a minimum distance of 1 and a maximum distance of
2, see Scenario 2: Levenshtein distance of 1 or 2 in first names

Scenario 2: Levenshtein distance of 1 or 2 in first names

This scenario is based on the scenario described above. Only the minimum and maximum
distance settings in the tFuzzyMatch component are
modified, which will change the output displayed.

In the Component view of the tFuzzyMatch, change the minimum distance from
0 to 1. This excludes straight away the exact matches (which would show a
distance of 0).
Change also the maximum distance to 2. The
output will provide all matching entries showing a discrepancy of 2 characters
at most.

No other changes are required.
Make sure the Matching item separator is
defined, as several references might be matching the main flow entry.
Save the new Job and press F6 to run
it.

As the edit distance has been set to 2,
some entries of the main flow match more than one reference entry.

You can also use another method, the metaphone, to assess the distance between the
main flow and the reference, which will be described in the next scenario.

Scenario 3: Metaphonic distance in first name

This scenario is based on the scenario described above.

Change the Matching type to Metaphone. There is no minimum nor maximum distance
to set as the matching method is based on the discrepancies with the phonetics
of the reference.
Save the Job and press F6. The phonetics
value is displayed along with the possible matches.

Document get from Talend https://help.talend.com

Thank you for watching.

Docs 5.x

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tFuzzyMatch – Docs for ESB 5.x