Re: query and pg_dump problem on my postgresql 6.5.3/Redhat 6.2

hi,
The disk just had problem, I used fsck to fix it, But the problem
of database is still there.
　　After I read the postgresql document and found this:
------
COPY stops operation at the first error. This should not lead to problems in the event of a COPY FROM, but the target relation will, of course, be partially modified in a COPY TO. The VACUUM query should be used to clean up after a failed copy.
------
Then I Execute the sql "vacuum newses;" in psql, it return this message:
------
NOTICE: Rel newses: Uninitialized page 16 - fixing
NOTICE: Rel newses: Uninitialized page 17 - fixing
VACUUM
------

It seems VACUUM fixed something, then I retry the SQL complained error before,
they all work well now, my php page work well also.

It's exciting that all problems is gone, but I'm still not clear about what
happened and what the VACUUM had done, anyone can explain it?

======= 2003-12-05 您在来信中写道：=======

>On Thursday 04 December 2003 14:55, 吴德文 wrote:
>> Help!
>>
>> A few days ago, my php page began to complain this:
>> ------
>> Warning: PostgresSQL query failed: pqReadData() -- backend closed the
>> channel unexpectedly. This probably means the backend terminated abnormally
>> before or while processing the request.
>[snip]
>> NOTE:
>> I'm on Redhat 6.2 with Postgresql 6.5.3, the database named "news",
>> and the table is "newses", looks like this (dumped from "pg_dump -s -t
>> newses news"):
>
>One of the developers will probably be able to help, but bear in mind many are
>in the USA/Canada and so you might have time-zone delays. It will be
>suggested you upgrade to 7.3.5 or 7.4.0 as soon as possible. That might mean
>upgrading from RedHat 6.2 as well.
>
>At present:
>1. Dump all the other tables, if you can
>2. Stop PostgreSQL
>3. make a file backup of /var/data (or wherever your data is stored)
>
>OK - now at least you know things can't get any worse.
>
>In psql you can use \a to set unaligned output and \o <filename> to output
>query results to a file. You can then try SELECT * FROM newses WHERE news_id
>BETWEEN 1 AND 100, then 101-200 etc. This should let you recover a great deal
>of your data if only one disk-block is damaged.
>
>From what you say, you should be able to recover your table's data. Then, I'd
>recreate the database from your dumps.
>
>> But I found that pg_dump sometimes does not work on that very table, and
>> sometimes work with a long long time then error.
>
>This sounds like either a disk or memory error. I'd guess disk.
>
>--
> Richard Huxton
> Archonet Ltd
>
>

= = = = = = = = = = = = = = = = = = = =

致
礼！

Wind Wood
windwood(at)jingxian(dot)xmu(dot)edu(dot)cn
2003-12-05