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From "Alex Behm (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-5309: Adds TABLESAMPLE clause for HDFS table refs.
Date Tue, 23 May 2017 05:42:24 GMT
Alex Behm has posted comments on this change.

Change subject: IMPALA-5309: Adds TABLESAMPLE clause for HDFS table refs.
......................................................................


Patch Set 3:

(3 comments)

http://gerrit.cloudera.org:8080/#/c/6868/4/fe/src/main/java/org/apache/impala/catalog/HdfsPartition.java
File fe/src/main/java/org/apache/impala/catalog/HdfsPartition.java:

Line 809:   public HdfsPartition cloneNewFds(List<FileDescriptor> newFds) {
> i don't think this is used anymore.
Done


http://gerrit.cloudera.org:8080/#/c/6868/3/fe/src/main/java/org/apache/impala/catalog/HdfsTable.java
File fe/src/main/java/org/apache/impala/catalog/HdfsTable.java:

Line 1961:     List<Pair<Long, FileDescriptor>> allFiles =
> i'd say it's cleaner than partition cloning, because the way the cloning wo
Returning as Map<Long, List<FileDescriptor>> now.


http://gerrit.cloudera.org:8080/#/c/6868/4/fe/src/main/java/org/apache/impala/catalog/HdfsTable.java
File fe/src/main/java/org/apache/impala/catalog/HdfsTable.java:

Line 1940:    * The 'percentBytes' parameter must be between 0 and 100.
> i'd also point out that it allocates something like 12+ bytes per existing 
That's definitely a legitimate concern. Added comment.

I also did another minor speed improvement to avoid unnecessarily doing a hash lookup to find
the partition of each selected file.

I'll run some experiments to see how this function performs.


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Gerrit-MessageType: comment
Gerrit-Change-Id: Ief112cfb1e4983c5d94c08696dc83da9ccf43f70
Gerrit-PatchSet: 3
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Alex Behm <alex.behm@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.behm@cloudera.com>
Gerrit-Reviewer: Marcel Kornacker <marcel@cloudera.com>
Gerrit-HasComments: Yes

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