Hash indexes can contain both pages which are all-zeroes (i.e.
PageIsNew()) and pages which have been initialized but currently
aren't used. The latter category can happen either when a page
has been reserved but not yet used or when it is used for a time
and then freed. pgstattuple was only prepared to deal with the
pages that are actually-zeroes, which it called zero_pages.
Rename the column to unused_pages (extension version 1.5 is
as-yet-unreleased) and make it count both kinds of unused pages.
Along the way, slightly tidy up the way we test for pages of
various types.
Robert Haas and Ashutosh Sharma, reviewed by Amit Kapila
Discussion: http://postgr.es/m/CAE9k0PkTtKFB3YndOyQMjwuHx+-FtUP1ynK8E-nHtetoow3NtQ@mail.gmail.com
Three nologin roles with non-overlapping privs are created by default
* pg_read_all_settings - read all GUCs.
* pg_read_all_stats - pg_stat_*, pg_database_size(), pg_tablespace_size()
* pg_stat_scan_tables - may lock/scan tables
Top level role - pg_monitor includes all of the above by default, plus others
Author: Dave Page
Reviewed-by: Stephen Frost, Robert Haas, Peter Eisentraut, Simon Riggs
Since pgstattuple v1.5 hasn't been released yet, no need for a new
extension version. The new function exposes statistics about hash
indexes similar to what other pgstatindex functions return for other
index types.
Ashutosh Sharma, reviewed by Kuntal Ghosh. Substantial further
revisions by me.
Now that we track initial privileges on extension objects and changes to
those permissions, we can drop the superuser() checks from the various
functions which are part of the pgstattuple extension and rely on the
GRANT system to control access to those functions.
Since a pg_upgrade will preserve the version of the extension which
existed prior to the upgrade, we can't simply modify the existing
functions but instead need to create new functions which remove the
checks and update the SQL-level functions to use the new functions
(and to REVOKE EXECUTE rights on those functions from PUBLIC).
Thanks to Tom and Andres for adding support for extensions to follow
update paths (see: 40b449a), allowing this patch to be much smaller
since no new base version script needed to be included.
Approach suggested by Noah.
Reviewed by Michael Paquier.
