From: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
---|---|
To: | Emmanuel Cecchet <manu(at)asterdata(dot)com> |
Cc: | Greg Smith <gsmith(at)gregsmith(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: COPY enhancements |
Date: | 2009-09-14 19:37:53 |
Message-ID: | 4AAE9B91.80805@dunslane.net |
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Lists: | pgsql-hackers |
Emmanuel Cecchet wrote:
> Greg Smith wrote:
>> On Fri, 11 Sep 2009, Emmanuel Cecchet wrote:
>>
>>> I guess the problem with extra or missing columns is to make sure
>>> that you know exactly which data belongs to which column so that you
>>> don't put data in the wrong columns which is likely to happen if
>>> this is fully automated.
>>
>> Allowing the extra column case is easy: everwhere in copy.c you find
>> the error message "extra data after last expected column", just
>> ignore the overflow fields rather than rejecting the line just based
>> on that. And the default information I mentioned you might want to
>> substitute for missing columns is already being collected by the code
>> block with the comment "Get default info if needed".
> If I understand it well, you expect the garbage to be after the last
> column. But what if the extra or missing column is somewhere upfront
> or in the middle? Sometimes you might have a type conflict problem
> that will help you detect the problem, sometimes you will just insert
> garbage. This might call for another mechanism that would log the
> lines that are automatically 'adjusted' to be able to rollback any
> mistake that might happen during this automated process.
>
>
Garbage off to the right is exactly the case that we have. Judging from
what I'm hearing a number of other people are too.
Nobody suggests that a facility to ignore extra columns will handle
every case. It will handle what increasingly appears to be a common case.
cheers
andrew
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