Re: High table creation rate results in “File exists” error

On Tue, Jan 21, 2020 at 02:04:24PM +0100, Radek Slupik wrote:
>Hi,
>
>We occasionally run into an internal error when creating tables. The error
>message is «could not create file "base/17006/2851173576": File exists»
>with SQLSTATE 58P02. The attachment is included with this email contains
>the PostgreSQL logs. Note that some identifiers are renamed in the logs
>because they contain sensitive information, but identifier names are
>unlikely the source of the error.
>
>An old mailing list thread [1] suggests a problem related to OID
>wraparound. Our use case involves creating and dropping thousands of tables
>every day. The CREATE TABLE statements for these tables are similar to the
>one in the attached logs, but with different table names and columns.
>Nonetheless, the error is difficult to reproduce as it happens only
>sporadically. Retrying the CREATE TABLE statement fixes the problem
>temporarily.
>
>Some more information about our PostgreSQL instance and usage:
>
>   - PostgreSQL version: PostgreSQL 10.6 (Ubuntu 10.6-1.pgdg16.04+1) on
>   x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.10) 5.4.0
>   20160609, 64-bit.
>   - The DBMS did not crash or abruptly shut down recently.
>   - The file base/17006/2851173576 was actually in use by an index, as
>   indicated by pg_class.relfilenode.
>   - Autovacuum is disabled for these tables. Logging is disabled for these
>   tables upon creation, but enabled after filling them with data.
>   - The query “SELECT max(oid) FROM pg_class” reports 4,294,603,797, which
>   is close to 2³² - 1.
>

So what was the actual rate of table creation? How long did it take to
get to this state?

What kernel/filesystem was used? What did lsof say?


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services