[jira] [Created] (IMPALA-14117) Select files only once for COMPUTE STATS with TABLESAMPLE clause

["Noémi Pap-Takács (Jira)" <ji...@apache.org>]

Noémi Pap-Takács created IMPALA-14117:
-----------------------------------------

             Summary: Select files only once for COMPUTE STATS with TABLESAMPLE clause
                 Key: IMPALA-14117
                 URL: https://issues.apache.org/jira/browse/IMPALA-14117
             Project: IMPALA
          Issue Type: Improvement
          Components: Frontend
            Reporter: Noémi Pap-Takács


In case of COMPUTE STATS, selecting the files to sample is done twice: first during analysis, then in the SCAN plan nodes. The first is necessary, because COMPUTE STATS needs to calculate the sampling to set the value of 'effectiveSamplePerc_' which is used in stats extrapolation to get more precise stats.

We could probably improve this, to always calculate the file samples once, during analysis, and then reuse the result in the SCAN plan node. 

 

In other cases, e.g. SELECT * FROM t TABLESAMPLE SYSTEM(10); we only calculate the sampling in the SCAN plan nodes.



--
This message was sent by Atlassian Jira
(v8.20.10#820010)

---------------------------------------------------------------------
To unsubscribe, e-mail: issues-all-unsubscribe@impala.apache.org
For additional commands, e-mail: issues-all-help@impala.apache.org