7.00.02 - Greedy Pattern Matching - Aster Analytics

Teradata Aster® Analytics Foundation User GuideUpdate 2

Product
Aster Analytics
Release Number
7.00.02
Published
September 2017
Content Type
Programming Reference
User Guide
Publication ID
B700-1022-700K
Language
English (United States)
Last Update
2018-04-17

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: