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From "Alex Behm (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] [PREVIEW] IMPALA-5058: Improve concurrency of DDL/DML operations
Date Thu, 16 Nov 2017 06:42:10 GMT
Alex Behm has posted comments on this change. ( http://gerrit.cloudera.org:8080/8545 )

Change subject: [PREVIEW] IMPALA-5058: Improve concurrency of DDL/DML operations
......................................................................


Patch Set 1:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/8545/1/fe/src/main/java/org/apache/impala/catalog/CatalogServiceCatalog.java
File fe/src/main/java/org/apache/impala/catalog/CatalogServiceCatalog.java:

http://gerrit.cloudera.org:8080/#/c/8545/1/fe/src/main/java/org/apache/impala/catalog/CatalogServiceCatalog.java@596
PS1, Line 596:       addTableToCatalogDeltaHelper(tbl, fromVersion, toVersion, resp);
> Maybe I'm misunderstanding something but I still see the lock contention on
I think your assessment is correct.

We are not trying to make getCatalogDelta() completely non-blocking. As you've correctly pointed
out it can still block on a table lock.

The problem we are trying to solve is that non-conflicting operations should not conflict.
Before this change the global lock was held for the entire duration of getCatalogDelta().
If a long-running operation is running against tbl A, and the thread executing getCatalogDelta()
needs to wait to get the table lock on A, then no concurrent DDL whatsoever is possible due
to the global lock. That's the main problem: a long running operation on A can prevent concurrent
DDL against anything else.



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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I3032437f83d39bcc8cff14d897c7c106a4ab62d3
Gerrit-Change-Number: 8545
Gerrit-PatchSet: 1
Gerrit-Owner: Dimitris Tsirogiannis <dtsirogiannis@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.behm@cloudera.com>
Gerrit-Reviewer: Bharath Vissapragada <bharathv@cloudera.com>
Gerrit-Comment-Date: Thu, 16 Nov 2017 06:42:10 +0000
Gerrit-HasComments: Yes

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