10-21-2017 10:27 AM - edited 10-21-2017 11:12 AM
In NameNode when I run the query via odbc script (php/perl or python), I can fetchAll results (9.2M) in a variable in about 30 seconds, but when I tried with the same script/query on another remote 2 servers, the execution time was in first server 28 min and in second 17 min.
To exclude the assuming that it's a network speed issue, I fetch the result on a file and then I copied it with scp command to the first remote server, and it finished in ~40 seconds.
What I observe in Query info in CM that there is a big different between the *Threads: Network Send Wait Time* values in the 3 queries :
in NN query: 9.40s
in 1st remote server: 16.7m
in 2nd remote server: 26.8m
And also I try an java script with Impala JDBC, but the results in NN are already not stimulate to continue.
But so far I cann't find where is the problem and how can I resolve it.
NB: I'm working on CDH 5.12.0/Impala 2.9.0, I installed Impala ODBC 126.96.36.1994.
Hope you can respode to me ASAP, because this issue is a realy an obstacle of using a cluster that we made a several months to make it.
Thanks in advance.
10-25-2017 03:55 AM
10-25-2017 05:06 AM
Thanks to your reply @EricL
I fetched same result of query on a file (about 500Mb), then I copied it with scp command to the first remote server, and it finished in ~40 seconds.
To elimine the probability that this issue is caused by a network speed, I have been copied the same results (9.2M) in a postgres table and test the fetchAll with postgres driver via unixODBC and it takes about 50 secs.
10-25-2017 06:41 PM
10-26-2017 05:06 AM
I already increase the RowsFetchedPerBlock and also TSaslTransportBufSize and no improvement :'(
In Additionally, the test of ODBC with postgresql driver is runed with the same value of this proprieties and give a good results (50 secs).
10-31-2017 03:22 AM - edited 10-31-2017 03:42 AM
Remark: I observe in ClouderaODBCDriverforImpala_connection_0.log file, that the PrepareTResultForDataRetrieval in the 2 cases repeats ~150 times, even if the RowsFetchedPerBlock is 10000 (it look like it fixed on 1024) !!!
10-31-2017 08:24 PM
10-31-2017 09:29 PM
11-01-2017 10:54 AM
Here is the profile of query and ODBC log files:
NN - ODBC logs - query 200k - 10s - 1.73s without log
Remote Server - ODBC logs - query 200k - 48s - 41s without log
Thanks in advance.
04-18-2018 02:27 AM
Finaly and after almost 6 months I have found the solution!
It was always about my 1024 limitition remark, the row batch limitation was from BATCH_SIZE max value (1024), in the last versions (CDH 5.14/Impala 2.11) we have a new effective range is 1-65536.
So when I increase it throgh a odbc.ini with SSP_BATCH_SIZE I can benifit from increasing the other odbc parameters (RowsFetchedPerBlock / TSaslTransportBufSize) and the rows can be fetched in a seconds (~45 secs) instead of tens of minutes.
Remark: I have been recreated the cluster in 3 different server providers and tested the connections from almost 5 others with different ODBC/JDBC releases etc.. and always I have the same slowness until this update came.
I can not understand why I'm the only on declared this big issue and why no one can answer me, kowning that it's realy depressed to have a good quering engine but a veeeery slow fetch rows!
Any way, thanks all for your replies.