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
