So I assume there is no redundant information stored such as checksum to
validate the files against the stored checksums.
I don't have an active issue. Just trying to understand in detail how Postgres
behaves under index corruption.
________________________________
From: Craig Ringer <ring...@ringerc.id.au>
To: A J <s5...@yahoo.com>
Cc: PG Admin <pgsql-admin@postgresql.org>
Sent: Friday, August 19, 2011 2:40 AM
Subject: Re: [ADMIN] Question on Postgres Index internals
On 19/08/2011 5:46 AM, A J wrote:
How does Postgres detect corruption of index data files ?
If their structure doesn't make sense, they're corrupt. It doesn't actively
seek or detect corruption, because it shouldn't happen, and cannot be reliably
discovered if it has.
What is the exact mechanism by which it knows that the index is corrupt ?
Numerous different ways, depending on the nature of the damage and the type of
index. Often it won't know the index is damaged at all.
Can it happen that part of the index is corrupt but Postgres does not realize
because those specific rows are not accessed (but other rows from that table
are accessed)
>
>
Yes, that is possible. It is also possible that a damaged index could cause
issues like multiple instances of a value that's supposed to be unique, or a
foreign key reference to a non-existent tuple.
Index corruption should not happen. If you are facing index
corruption, either you have a hardware problem or you've hit a bug.
The vast majority of cases are hardware faults.
Perhaps it'd help if you'd supply a little more detail about the
background. Why you're asking this, and why you (presumably) suspect
you have index corruption.
--
Craig Ringer
