DawnZhang created KUDU-2231:
-------------------------------
Summary: "materializing_iterator_do_pushdown=true" cause simple
query slow
Key: KUDU-2231
URL: https://issues.apache.org/jira/browse/KUDU-2231
Project: Kudu
Issue Type: Bug
Components: master, tserver
Affects Versions: 1.5.0, 1.4.0
Environment: CentOS release 6.5 (2.6.32-431.11.9.el6.ucloud.x86_64)
KUDU-1.4.0-1.cdh5.12.1.p0.10
IMPALA 2.6.0
x86-64
Intel CPU
Reporter: DawnZhang
Attachments: 756ACA6F105F0905EBCB79B940FFCE86.jpg,
F8C604537B8E921DDCCA78995DC11BDA.jpg
I ran the following SQL again and again
while refresh 8050/scans page at the same time.
sql:
{code:sql}
select count(xx_id),count(xx_id),count(time) from test_table where event_id
=29983;
{code}
"Cells read from disk" is much more greater then table size when
materializing_iterator_do_pushdown = true (default).
after setting materializing_iterator_do_pushdown = false
"Cells read from disk" reduced to some reasonable value (close to table size)
and the sql run faster.
here's detail:
table under test:
{code:sql}
CREATE TABLE rawdata.test_table (
day INT NOT NULL ENCODING BIT_SHUFFLE COMPRESSION DEFAULT_COMPRESSION,
user_id BIGINT NOT NULL ENCODING BIT_SHUFFLE COMPRESSION DEFAULT_COMPRESSION,
time TIMESTAMP NOT NULL ENCODING BIT_SHUFFLE COMPRESSION DEFAULT_COMPRESSION,
event_id INT NULL ENCODING BIT_SHUFFLE COMPRESSION DEFAULT_COMPRESSION,
distinct_id STRING NULL ENCODING DICT_ENCODING COMPRESSION
DEFAULT_COMPRESSION,
...
... other fields ...
...
PRIMARY KEY (day, user_id, time, _offset)
)
PARTITION BY HASH (user_id) PARTITIONS 9
STORED AS KUDU
TBLPROPERTIES ( ... );
{code}
table size (select count(1) from test_table) : 19510709
CASE 1, materializing_iterator_do_pushdown = true
scans:
!756ACA6F105F0905EBCB79B940FFCE86.jpg|thumbnail!
CASE 2, materializing_iterator_do_pushdown = false (sql ran faster)
scans:
!F8C604537B8E921DDCCA78995DC11BDA.jpg|thumbnail!
it looks like kudu scan table multiple times for the simple sql caused by some
silly bug.
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