Use Cases of Row Pattern Matching in Oracle 12c

BASEL BERN BRUGG DÜSSELDORF FRANKFURT A.M. FREIBURG I.BR. GENF

HAMBURG KOPENHAGEN LAUSANNE MÜNCHEN STUTTGART WIEN ZÜRICH

Use Cases of Row Pattern MatchingWebinar on MATCH_RECOGNIZE as a versatile SQL tool

Kim Berg HansenSenior Consultant

• Danish geek

• SQL & PL/SQL developer since 2000

• Developer at Trivadis AG since 2016

http://www.trivadis.dk

• Oracle Certified Expert in SQL

• Oracle ACE

• Blogger at http://www.kibeha.dk

• SQL quizmaster at

http://plsqlchallenge.oracle.com

• Likes to cook

• Reads sci-fi

• Chairman of local chapter of

Danish Beer Enthusiasts

About me

Use Cases of Row Pattern Matching2 2/23/2016

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Agenda


Brief syntax overview

1. Grouping contiguous sequences

2. Grouping by time range (I)

3. Grouping by time range (II)

4. Merge date ranges

5. Group with limit on aggregate (bin fitting I)

6. Fill bins to near equal size (bin fitting II)

7. Network hickups

8. Tablespace growth spurts

9. Hierarchical child count

Brief summary

Q & A


Brief syntax overview

What‘s it look like

Think in Patterns8 2/23/2016

SELECT *

FROM Ticker MATCH_RECOGNIZE (

PARTITION BY symbol

ORDER BY tstamp

MEASURES STRT.tstamp AS start_tstamp,

FINAL LAST(DOWN.tstamp) AS bottom_tstamp,

FINAL LAST(UP.tstamp) AS end_tstamp,

MATCH_NUMBER() AS match_num,

CLASSIFIER() AS var_match

ALL ROWS PER MATCH

AFTER MATCH SKIP TO LAST UP

PATTERN (STRT DOWN+ UP+)

DEFINE

DOWN AS DOWN.price < PREV(DOWN.price),

UP AS UP.price > PREV(UP.price)

) MR

ORDER BY MR.symbol, MR.match_num, MR.tstamp

Example from Data Warehousing Guide chapter on SQL For Pattern Matching

The result

Think in Patterns9 2/23/2016

SYMBOL TSTAMP START_TST BOTTOM_TS END_TSTAM MATCH_NUM VAR_ PRICE

---------- --------- --------- --------- --------- ---------- ---- ----------

ACME 05-APR-11 05-APR-11 06-APR-11 10-APR-11 1 STRT 25

ACME 06-APR-11 05-APR-11 06-APR-11 10-APR-11 1 DOWN 12

ACME 07-APR-11 05-APR-11 06-APR-11 10-APR-11 1 UP 15













The output of the example in the previous slide

Elements


PARTITION BY – like analytics split data to work on one partition at a time

ORDER BY – in which order shall rows be tested whether they match the pattern

MEASURES – the information we want returned from the match

ALL ROWS / ONE ROW PER MATCH – return aggregate or detailed info for match

AFTER MATCH SKIP … – when match found, where to start looking for new match

PATTERN – regexp like syntax of pattern of defined row classifiers to match

SUBSET – „union“ a set of classifications into one classification variable

DEFINE – definition of classification of rows

FIRST, LAST, PREV, NEXT – navigational functions

CLASSIFIER(), MATCH_NUMBER() – identification functions


9 use cases

9 Demos



Brief summary

MATCH_RECOGNIZE - A “swiss army knife” tool


Brilliant when applied “BI style” like stock ticker analysis examples

But applicable to many other cases too

When you have some problem crossing row boundaries and feel you have to

“stretch” even the capabilities of analytics, try a pattern based approach:

– Rephrase (in natural language) your requirements in terms of what classifies the

rows you are looking for

– Turn that into pattern matching syntax classifying individual rows in DEFINE and

how the classified rows should appear in PATTERN

As with analytics, it might feel daunting at first, but once you start using pattern

matching, it will become just another tool in your SQL toolbox


Further information

Demo scripts used in this webinar

– http://bit.ly/patternmatchsamples

Follow Stew Ashton’s blog posts on the topic

– https://stewashton.wordpress.com/category/match_recognize/

Documentation in Data Warehousing Guide

– http://docs.oracle.com/database/121/DWHSG/pattern.htm

http://bit.ly/patternmatchsamples

https://stewashton.wordpress.com/category/match_recognize/

http://docs.oracle.com/database/121/DWHSG/pattern.htm#DWHSG8956

Q & AKim Berg Hansen

Senior Consultant

[email protected]

2/23/2016 Use Cases of Row Pattern Matching16

Software

Use Cases of Row Pattern Matching in Oracle 12c