Index contains unexpected zero page at block

Victor Blomqvist <vb@viblo.se> writes:

From time to time I get this and similar errors in my Postgres log file:

< 2015-12-17 07:45:05.976 CST >ERROR: index
"user_pictures_picture_dhash_idx" contains unexpected zero page at block
123780

Hm, can't tell for sure from the error message text, but the index name
suggests that this is a hash index?

The server is a read slave, set up with streaming replication. We run
PostgreSQL 9.3.5.

Hash indexes are not WAL-logged, which means their contents do not
propagate to slave servers, which basically means you cannot use them
in replication setups.

Will it be fixed with a newer version of Postgres?

Adding WAL-logging to hash indexes has been on the to-do list for a long
time; but it's never gotten done, in part because there has never been
any clear evidence that hash indexes are better than btree indexes for
any real-world purpose. I'm curious why you chose this index type in
the first place.

regards, tom lane

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Sorry, I should have included the index definition, its a normal btree
index on a bigint column:

CREATE INDEX user_pictures_picture_dhash_idx
ON user_pictures
USING btree
(picture_dhash);

And the table itself:
CREATE TABLE user_pictures (picture_dhash bigint)
(and ~10 other columns not relevant for this I think)

/Victor

On Thu, Dec 17, 2015 at 12:22 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

On Wed, Dec 16, 2015 at 9:48 PM, Victor Blomqvist <vb@viblo.se> wrote:

From time to time I get this and similar errors in my Postgres log file:

< 2015-12-17 07:45:05.976 CST >ERROR: index
"user_pictures_picture_dhash_idx" contains unexpected zero page at block
123780
< 2015-12-17 07:45:05.976 CST >HINT: Please REINDEX it.
< 2015-12-17 07:45:05.976 CST >CONTEXT: PL/pgSQL function
select_pictures_by_dhash(bigint,integer,integer) line 3 at RETURN QUERY
< 2015-12-17 07:45:05.976 CST >STATEMENT: SELECT * FROM
select_pictures_by_dhash(8559245352688506666,100,0)

I have tried to recreate the index (create new index, drop the old one), but
it doesnt help, the error comes back anyway. Also, its not there all the
time, when I tried to rerun the statement from the logfile above a couple of
hours later it worked fine without any error.

The server is a read slave, set up with streaming replication. We run
PostgreSQL 9.3.5.

Step #1: Install 9.3.10 on both servers.

If the issue is still then reproducing, then this problem gets a lot
more interesting. Are you running with checksums on?

merlin

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