Thank you anyway, Michael!--2015-06-26 17:21 GMT-07:00 Michael McAllister <firstname.lastname@example.org>:
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!
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 <email@example.com>:
Have you tried using the EXPLAIN command to see what plan is being used to access the data?
Staff Data Warehouse Engineer | Decision Systems
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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?