Tom Lane wrote:
> No, it probably means that neither one has been written at all yet.
> Typically, when a WAL segment is deemed no longer needed, the file isn't
> physically removed but is merely renamed into place as a future segment.
> The idea is to reduce unnecessary filesystem work as we create and delete
> WAL segments. You could check this out if you have pg_xlogdump at hand,
> by seeing whether the WAL file's first page header claims to belong to the
> segment indicated by the file name, or to some much-older segment.
This may be a good time to point out that pg_xlogdump fails completely
when a file's contents does not match the file name, with no indication
about what a better file name would be. In other words, if a file has
been recycled and not written to yet under the new name, it doesn't tell
you anything useful. This is pretty annoying.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services