Re: Does PostgreSQL check database integrity at startup?

Em 26/12/2017 20:11, rob stone escreveu:
> Hello,
>
>
> On Tue, 2017-12-26 at 18:58 -0300, Alvaro Herrera wrote:Hello,
>> David Steele wrote:
>>
>>> pgBackRest will validate all page checksums (including indexes,
>>> etc.) in the
>>> cluster during backup.  Full backups check everything,
>>> incr/differential
>>> backups check only the files that have changed.
>> If a table or index file is of zero length when backed up, as in the
>> described case, nothing will be checked, right?  I mean, there is
>> nothing externally indicating that the file ought to be of a
>> different
>> size.  Am I wrong?  So Edson's situation here would not raise any red
>> flags.
>>
>
> Could the following occur:-
> 1) Your app. issues a BEGIN followed by an INSERT.
> 2) Postgres decides to open a new file in order to store the new row.
> 3) Your app. then does a ROLLBACK.
>
> Wouldn't that leave you with a zero length file on disk?
>
> There's no reason for Postgres to delete the file just because a
> rollback was issued. All it has to do is clear the buffer in memory.
>
> My 2 cents.
>
> Rob
>
>

You are right, in several databases I've looked there are many files 
with 0 byte size in ./base folder.
This is not a good quest.

Regards,

Edson