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From "Balazs Jeszenszky (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-5310: Add COMPUTE STATS TABLESAMPLE.
Date Wed, 27 Sep 2017 09:58:19 GMT
Balazs Jeszenszky has posted comments on this change. ( http://gerrit.cloudera.org:8080/8136
)

Change subject: IMPALA-5310: Add COMPUTE STATS TABLESAMPLE.
......................................................................


Patch Set 1:

(4 comments)

http://gerrit.cloudera.org:8080/#/c/8136/1//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/8136/1//COMMIT_MSG@24
PS1, Line 24: Limitations
add: only for HDFS tables


http://gerrit.cloudera.org:8080/#/c/8136/1//COMMIT_MSG@25
PS1, Line 25: --enable_stats_extrapolation=true
Is this really required to be a startup option, wouldn't a query option (SET) work? I expect
it will be enabled most of the time, and disabling it would be a troubleshooting step or workaround
for some issues, particularly in planning. It would be better not to have to restart to do
that.


http://gerrit.cloudera.org:8080/#/c/8136/1/fe/src/main/java/org/apache/impala/analysis/ComputeStatsStmt.java
File fe/src/main/java/org/apache/impala/analysis/ComputeStatsStmt.java:

http://gerrit.cloudera.org:8080/#/c/8136/1/fe/src/main/java/org/apache/impala/analysis/ComputeStatsStmt.java@67
PS1, Line 67: Stats extrapolation disabled
How would Impala behave if stats are computed with TABLESAMPLE, and then stats extrapolation
is disabled?


http://gerrit.cloudera.org:8080/#/c/8136/1/fe/src/main/java/org/apache/impala/planner/HdfsScanNode.java
File fe/src/main/java/org/apache/impala/planner/HdfsScanNode.java:

http://gerrit.cloudera.org:8080/#/c/8136/1/fe/src/main/java/org/apache/impala/planner/HdfsScanNode.java@777
PS1, Line 777: if (totalBytes_ == 0) {
totalBytes_ doesn't get a new value in the above section, why not make this check at the beginning,
as it was?



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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I7f3e72471ac563adada4a4156033a85852b7c8b7
Gerrit-Change-Number: 8136
Gerrit-PatchSet: 1
Gerrit-Owner: Alex Behm <alex.behm@cloudera.com>
Gerrit-Reviewer: Balazs Jeszenszky <jeszyb@gmail.com>
Gerrit-Reviewer: Dimitris Tsirogiannis <dtsirogiannis@cloudera.com>
Gerrit-Reviewer: Vuk Ercegovac <vercegovac@cloudera.com>
Gerrit-Comment-Date: Wed, 27 Sep 2017 09:58:19 +0000
Gerrit-HasComments: Yes

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