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 <yliu33@kent.edu>:
Thank you anyway, Michael!

2015-06-26 17:21 GMT-07:00 Michael McAllister <mmcallister@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:yliu33@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 <mmcallister@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

mmcallister@HomeAway.com | C: 512.423.7447 | skype: michael.mcallister.ha | webex: https://h.a/mikewebex

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:yliu33@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