Hi Dongwon, I'm not super familiar with Flink's MATCH_RECOGNIZE support, but Dawid (in CC) might have some ideas about it.
Best, Fabian Am Mi., 21. Aug. 2019 um 07:23 Uhr schrieb Dongwon Kim < eastcirc...@gmail.com>: > Hi, > > Flink relational apis with MATCH_RECOGNITION looks very attractive and > promising but it's currently not easy to use at all. > > While looking into [1], > especially the following DEFINE clause, > >> DEFINE >> PRICE_DOWN AS >> (LAST(PRICE_DOWN.price, 1) IS NULL AND PRICE_DOWN.price < START_ROW.price >> ) OR PRICE_DOWN.price < LAST(PRICE_DOWN.price, 1), >> PRICE_UP AS >> PRICE_UP.price > LAST(PRICE_DOWN.price, 1) > > what came up to my mind is that the condition is quite verbose. > > Meanwhile, I found [2] in which Oracle uses the similar data and the > MATCH_RECOGNIZE clause as follows: > >> SELECT * >> FROM Ticker MATCH_RECOGNIZE ( >> PARTITION BY symbol >> ORDER BY tstamp >> MEASURES STRT.tstamp AS start_tstamp, >> LAST(DOWN.tstamp) AS bottom_tstamp, >> LAST(UP.tstamp) AS end_tstamp >> ONE ROW 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.start_tstamp; >> >> Oracle's way of defining pattern variables looks much simple and neat > thanks to > 1) its use of PREV which is not available in Flink's MATCH_RECOGNIZE > clause (mentioned in [3]) > 2) no need to check the initial case or when there is no last row that met > the PRICE_DOWN condition > > Is there a way to shorten the DEFINE cluase in MATCH_RECOGNIZE at Flink > 1.8 or 1.9? > If there's any plan regarding this, could anyone let me know related Jira > issues? > > Best, > Dongwon > > [1] > https://ci.apache.org/projects/flink/flink-docs-stable/dev/table/streaming/match_recognize.html#introduction-and-examples > [2] https://docs.oracle.com/database/121/DWHSG/pattern.htm > [3] > https://ci.apache.org/projects/flink/flink-docs-stable/dev/table/streaming/match_recognize.html#known-limitations > >
