CodeGen way to slow

[#1]

Hi, 
using impala 2.7(8) with cdh5.10.1 here. 
I am trying a simple query : 
`select distinct(date_col_partition) from table_1`

and it is taking 20 sec. 
But When I do a set DISABLE_CODEGEN=true;

It take only less than a second. 

here is the profle gist: https://gist.github.com/anonymous/1a5faa3a10d4495f7b8abc3c964457db

Any idea of what is going wrong?

thanks

[#2]

Hi Maurin,

thanks for posting, this is pretty interesting. What is the type of your "cuberon_event_date" column?

Alex

[#3]

As an experiment, it would be interesting to try the query with the same data using a different data format, e.g., text. You can do a quick CREATE TABLE test as SELECT * FROM <original_table> and the retry the query.

[#4]

It is a string of that look like "YYYY-MM-DD"
the table is stored as avro. I can try using parquet or text if you want

[#5]

Thanks. Trying Parquet would help. Just want to see of the high optimization time in codegen is due to some glitch for Avro.

[#6]

Does the table have a lot of columns or anything unusual like that?

[#7]

it seems to be coming from avro. 
I created the table as parquet and it took 0.48sec.
The table have about 900 columns, so nothing to fancy.

thanks

[#8 · Accepted solution]

Thanks for investigating. We've confirmed internally that the issue is related to Avro with many columns. 900 is somewhat wide.

Thanks for reporting! We'll continue to look into this issue.

[#9]

thanks!
If you open a jira, can you send me the link?
I will probably disable codegen for now. And wait until you push a fix to re enable it. 
thanks

[#10]

https://issues.apache.org/jira/browse/IMPALA-5243