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From "Amos Bird (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-1654: DDL for multiple partitions
Date Thu, 19 Jan 2017 02:13:17 GMT
Amos Bird has posted comments on this change.

Change subject: IMPALA-1654: DDL for multiple partitions
......................................................................


Patch Set 3:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/5726/3/docs/topics/impala_alter_table.xml
File docs/topics/impala_alter_table.xml:

Line 144:       For example, you might drop a group of partitions corresponding to a particular
date
> Does the scalability bottleneck apply when the number of matching partition
>Does the scalability bottleneck apply when the number of matching partitions is high,
or just generally when the table has a lot of partitions regardless of how many match?

when there are a lot of matching partitions.

>Do we have any guidance to offer (e.g. "don't use this idiom on tables with tens of thousands
of partitions", or "under circumstances XYZ, issue multiple ALTER TABLE statements, each for
one partition")?

well it just acts like we are issueing multiple single DROP stmts, so there isn't a guidance.
User has to pay such laytency for now if those partitions are needed to be dropped.

>Does any issue manifest itself just as a single slow DDL statement, or does the hms traffic
potentially cause other statements to wait, or other symptoms?

it's holding a lock of targeting table, so other DDLs related will be blocked.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I2060552d5081e5f93b1b1f398414c52fa03f215b
Gerrit-PatchSet: 3
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: John Russell <jrussell@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.behm@cloudera.com>
Gerrit-Reviewer: Amos Bird <amosbird@gmail.com>
Gerrit-Reviewer: John Russell <jrussell@cloudera.com>
Gerrit-HasComments: Yes

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