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From "Binh Luong" <blnr...@gmx.de>
Subject Re: Bad performance of the first resultset.next()
Date Thu, 20 Apr 2017 11:12:06 GMT
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<div>Hi Josh,<br/>
thank you for your answer.<br/>
Yes, I am using HDP 2.3.4. You&#39;re right, with the newer versions it may improve the
performance significantly. However, we are going to have a release shortly, so now it&#39;s
not possible for an upgrade. But yes, it should happen in the upcoming application release.</div>

<div>The table has 21 columns:<br/>
- the first 3 (id,type and timestamp) make up the PK<br/>
- the following 18 columns are unsigned int.</div>

<div>No, there is no secondary indexes defined for the table.<br/>
An example query:<br/>
SELECT timestamp,VALUE04,VALUE15<br/>
FROM T.TABELLE<br/>
WHERE id=&#39;ID1&#39; and type=&#39;A&#39; and timestamp&gt;=TO_TIMESTAMP(&#39;...&#39;)
timestamp&lt;=TO_TIMESTAMP(&#39;...&#39;)<br/>
ORDER BY id ASC, type ASC, timestamp ASC;</div>

<div>Explain plan:<br/>
&#124; CLIENT 7-CHUNK PARALLEL 7-WAY RANGE SCAN OVER T.TABELLE [0,&#39;ID1&#39;,&#39;A&#39;,&#39;2015-12-02
00:00:00.000&#39;] - [0,&#39;ID1&#39;,&#39;A&#39;,&#39;2017-01-01
00:00:00.000&#39;]<br/>
&#124; &nbsp; &nbsp; SERVER FILTER BY (A.VALUE04 IS NOT NULL OR A.VALUE15 IS NOT
NULL)<br/>
&#124; CLIENT MERGE SORT</div>

<div>It looks like you suspect that phoenix is firstly reading the data and then post-filtering
/ sorting the data.&nbsp;</div>

<div>But why it take sometimes so much time in the first next() call?</div>

<div>When I try to send the request sequentially, the 1.next() always takes about less
than 200 ms for processing. But when a large number of requests are coming in parallel, the
processing time is increasing significantly to even more than 20, 30 secs.&nbsp;</div>

<div>Is it something relating to HBase, as the table is minor compacted from time to
time and it has impact to the read performance?&nbsp;<br/>
I am not sure how the next() call is implemented in the phoenix 4.4.0? Which component can
be the bottleneck in such concurrent processing scenario?&nbsp;</div>

<div>Thanks in advance<br/>
Lee</div>
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