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From Ming Li <...@pivotal.io>
Subject Re: COPY command for external tables
Date Thu, 28 Jul 2016 09:13:25 GMT
Great idea.

Thinking that COPY command can tolerate error lines, if we want to support
COPY in a transaction, we need to regard each line as sub-transaction,
otherwise the whole transaction need to be rollbacked after error line
occurs. i.e. we need create a SAVEPOINT before processing one line, and if
error occurs, we should ROLLBACK TO SAVEPOINT.

Support transaction in this way will definitely slow down performance, I
suggest that add one option to switch transaction mode and non-transaction


On Thu, Jul 28, 2016 at 6:53 AM, Oleksandr Diachenko <odiachenko@pivotal.io>

> Hi,
> Recently we discovered that COPY command for external tables is not
> transactional.
> It means if user is running COPY command and during this process underlying
> HDFS fails - the end state of table is inconstant.
> As a result I filled a JIRA -
> https://issues.apache.org/jira/browse/HAWQ-956
> .
> From user perspective, COPY command might also need to support additional
> options, to make import/export process more flexible.
>    - Number of error lines to tolerate.
>    - Batch size to commit.
>    - TBD
> Please feel free to join discussion.
> Regards, Alex.

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