cdh 6.1 impala 3.1 kudu 1.8 1 masternode + 5 datanode all nodes 8 core 64g, ssd   create table test_like(id bigint, full_id string, primary key(id)) stored as kudu -- insert about 1k records, what ever they are ...... select count(*) from test_like t1 left join test_like t2 on t1.full_id like t2.full_id   It takes 13 seconds to execute:   [data-60:21000] gslq4dev_iquantity> select count(*) from test_like t1 left join test_like t2 on t1.full_id like t2.full_id ; Query: select count(*) from test_like t1 left join test_like t2 on t1.full_id like t2.full_id Query submitted at: 2019-02-21 13:44:55 (Coordinator: http://data-60:25000) Query progress can be monitored at: http://data-60:25000/query_plan?query_id=594efea080891f13:9e932ad900000000 +----------+ | count(*) | +----------+ | 1023 | +----------+ Fetched 1 row(s) in 13.54s [data-60:21000] gslq4dev_iquantity> summary; +---------------------+--------+----------+----------+-------+------------+-----------+---------------+---------------------------------+ | Operator | #Hosts | Avg Time | Max Time | #Rows | Est. #Rows | Peak Mem | Est. Peak Mem | Detail | +---------------------+--------+----------+----------+-------+------------+-----------+---------------+---------------------------------+ | 06:AGGREGATE | 1 | 0ns | 0ns | 1 | 1 | 16.00 KB | 10.00 MB | FINALIZE | | 05:EXCHANGE | 1 | 0ns | 0ns | 1 | 1 | 16.00 KB | 16.00 KB | UNPARTITIONED | | 03:AGGREGATE | 1 | 0ns | 0ns | 1 | 1 | 267.00 KB | 10.00 MB | | | 02:NESTED LOOP JOIN | 1 | 13.42s | 13.42s | 1.02K | -1 | 279.00 KB | 2.00 GB | LEFT OUTER JOIN, BROADCAST | | |--04:EXCHANGE | 1 | 0ns | 0ns | 1.02K | -1 | 136.00 KB | 56.99 KB | BROADCAST | | | 01:SCAN KUDU | 1 | 4.00ms | 4.00ms | 1.02K | -1 | 127.00 KB | 384.00 KB | gslq4dev_iquantity.test_like t2 | | 00:SCAN KUDU | 1 | 0ns | 0ns | 1.02K | -1 | 127.00 KB | 384.00 KB | gslq4dev_iquantity.test_like t1 | +---------------------+--------+----------+----------+-------+------------+-----------+---------------+---------------------------------+ all the time spent on nested loop join   This is a demo sql , in the real scene I want to get some rows and all their children using the full_id field full_id is in form of "1.2.3.4", and i have to use "like" operation to get the children( multi level) The record count in real table is far more than 1k, and it never finish   why is it so slow?  how to improve it?       ... View more

kudu1.7.0 in cdh 5.15 3 master nodes, 4c32g, ubuntu16.04  3 data nodes, 8c64g, 1.8T ssd, ubuntu16.04   It is a small table: project_spot, 5.93K records, 38 columns I found some slow sql on it（more than 400ms）, most time spend on MaterializeTupleTime  So i check the scan page on kudu tablet server web ui, and found this: It is a very small scan, but spend 423ms, why?   More information: I check the io performance on all data nodes using fio, no problem found: read : io=6324.4MB, bw=647551KB/s, iops=161887, runt= 10001msec There are 3 data nodes, only data02 has the problem. I reboot the tablet server on data02, not work ... View more