I used the HBase reverse scan to find the last row on the index table. It returned the expected result. I would like to know is Phoenix's "ORDER BY" and "DESC" implemented based on HBase reverse scan?
2015-06-26 17:25 GMT-07:00 Yufan Liu <yli...@kent.edu>: > Thank you anyway, Michael! > > 2015-06-26 17:21 GMT-07:00 Michael McAllister <mmcallis...@homeaway.com>: > >> OK, I’m a Phoenix newbie, so that was the extent of the advice I could >> give you. There are people here far more experienced than I am who should >> be able to give you deeper advice. Have a great weekend! >> >> >> >> Mike >> >> >> >> *From:* Yufan Liu [mailto:yli...@kent.edu] >> *Sent:* Friday, June 26, 2015 7:19 PM >> *To:* user@phoenix.apache.org >> *Subject:* Re: Problem in finding the largest value of an indexed column >> >> >> >> Hi Michael, >> >> Thanks for the advice, for the first one, it's "CLIENT 67-CHUNK PARALLEL >> 1-WAY FULL SCAN OVER TIMESTAMP_INDEX; SERVER FILTER BY FIRST KEY ONLY; >> SERVER AGGREGATE INTO SINGLE ROW" which is as expected. For the second one, >> it's "CLIENT 67-CHUNK SERIAL 1-WAY REVERSE FULL SCAN OVER TIMESTAMP_INDEX; >> SERVER FILTER BY FIRST KEY ONLY; SERVER 1 ROW LIMIT" which looks correct, >> but still returns the unexpected result. >> >> >> >> 2015-06-26 16:59 GMT-07:00 Michael McAllister <mmcallis...@homeaway.com>: >> >> Yufan >> >> >> >> Have you tried using the EXPLAIN command to see what plan is being used >> to access the data? >> >> >> >> Michael McAllister >> >> Staff Data Warehouse Engineer | Decision Systems >> >> mmcallis...@homeaway.com | C: 512.423.7447 | skype: michael.mcallister.ha >> <zimmk...@hotmail.com> | webex: https://h.a/mikewebex >> >> [image: Description: Description: cid:3410354473_30269081] >> >> This electronic communication (including any attachment) is >> confidential. If you are not an intended recipient of this communication, >> please be advised that any disclosure, dissemination, distribution, copying >> or other use of this communication or any attachment is strictly >> prohibited. If you have received this communication in error, please >> notify the sender immediately by reply e-mail and promptly destroy all >> electronic and printed copies of this communication and any attachment. >> >> >> >> *From:* Yufan Liu [mailto:yli...@kent.edu] >> *Sent:* Friday, June 26, 2015 6:31 PM >> *To:* user@phoenix.apache.org >> *Subject:* Problem in finding the largest value of an indexed column >> >> >> >> Hi, >> >> We have created a table (eg, t1), and a global index of one numeric >> column of t1 (eg, timestamp). Now we want to find the largest value of >> timestamp, we have tried two approaches: >> >> >> 1. select max(timestamp) from t1; This query takes forever to finish, so >> I think it maybe doing a full table scan/comparison . >> >> 2. select timestamp from t1 order by timestamp desc limit 1; This query >> finished fast, but the result it returns is far from the largest value. It >> seems it just return the largest value for a certain range of data. >> >> Did anyone else encounter this issue/have any suggestion? >> >> >> -- >> >> Thanks, >> >> Yufan >> >> >> >> >> -- >> >> best, >> Yufan >> > > > > -- > best, > Yufan > > -- best, Yufan
