Greedy Pattern Matching - Aster Analytics

Teradata Aster® Analytics Foundation User GuideUpdate 2

Product
Aster Analytics
Release Number
7.00.02
Published
September 2017
Language
English (United States)
Last Update
2018-04-17
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dita:id
B700-1022
lifecycle
previous
Product Category
Software

The nPath function uses greedy pattern matching, finding the longest available match despite any nongreedy operators in the pattern.

For example, consider the input table link2:

nPath Greedy Pattern Matching Examples Input Table link2
userid title startdate enddate
21 Chief Exec Officer 1994-10-01 2005-02-28
21 Software Engineer 1996-10-01 2001-06-30
21 Software Engineer 1998-10-01 2001-06-30
21 Chief Exec Officer 2005-03-01 2007-03-31
21 Chief Exec Officer 2007-06-01 null

The following query returns the following table:

SELECT job_transition_path, count(*) AS count FROM nPath (
  ON link2 PARTITION BY userid ORDER BY startdate
  Mode (NONOVERLAPPING)
  Pattern ('CEO.ENGR.OTHER*')
  Symbols (title ilike 'software eng%' AS ENGR,
    true AS OTHER,
    title ilike 'Chief Exec Officer' AS CEO)
  Result (accumulate(title OF ANY(ENGR,OTHER,CEO))
    AS job_transition_path)
) GROUP BY 1 ORDER BY 2 DESC;
nPath Greedy Pattern Matching Example 1 Output Table
job_transition_path count
[Chief Exec Officer, Software Engineer, Software Engineer, Chief Exec Officer, Chief Exec Officer] 1

In the pattern, CEO matches the first row, ENGR matches the second row, and OTHER* matches the remaining rows:



The following query returns the following table:

SELECT job_transition_path, count(*) AS count FROM nPath (
  ON link2 PARTITION BY userid ORDER BY startdate
  Mode (NONOVERLAPPING)
  Pattern ('CEO.ENGR.OTHER*.CEO')
  Symbols (title ilike 'software eng%' AS ENGR,
    true AS OTHER,
    title ilike 'Chief Exec Officer' AS CEO)
  Result (accumulate(title of ANY(ENGR,OTHER,CEO))
    AS job_transition_path)
) GROUP BY 1 ORDER BY 2 DESC;
nPath Greedy Pattern Matching Example 2 Output Table
job_transition_path count
[Chief Exec Officer, Software Engineer, Software Engineer, Chief Exec Officer, Chief Exec Officer] 1

In the pattern, CEO matches the first row, ENGR matches the second row, OTHER* matches the next two rows, and CEO matches the last row: