Re: Add pgstathashindex() to get hash index table statistics.

On Wed, Feb 1, 2017 at 10:13 PM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
> On Tue, Jan 24, 2017 at 8:36 PM, Kuntal Ghosh
> <kuntalghosh(dot)2007(at)gmail(dot)com> wrote:
>> Nothing else to add from my side. I'm marking this 'Ready for commiter'.
>
> Moved to CF 2017-03 with the same status.

OK, I took a look at this.

- The handling of the extension stuff wasn't correct. You can't go
back and modify version 1.4; that's already been released. But
version 1.5 hasn't been released yet, so we can (and should) add more
stuff to that version instead of creating a new version. We don't
need the pushups that you did with superuser checks, because there's
no version out there in the wild that has those checks, so users with
installed binaries can't be relying on them. I cleaned all that stuff
up, which made this significantly simpler.

- I removed several of the columns being returned from the metapage.
The pageinspect code that I committed yesterday can be used to look at
those values; there doesn't seem to be a need to also return them
here. What this is really useful for is getting the "real" values by
scanning through the whole index and tallying things up.

- I adjusted some of the data types, both in the SQL and in the C
code, so that they all match and that they're wide enough to return
the values they might contain without overflowing (but not wider). I
also made the free_percent float8 rather than float4, consistent with
other things in this module. One thing I cheated on slightly: I left
the version as int4 rather than int8 even though the underlying field
is uint32, for consistency with everything else in this module.
That's not entirely intellectually satisfying, but I guess it's better
to be consistent for the moment.

- I fixed a number of cosmetic issues, like the fact that the
documentation for this didn't use \x format, unlike all of the other
pgstattuple documentation, and the fact that table_len isn't a very
good name for a variable representing the total amount of space for
tuples, and the fact that the documentation referred to a hash index
as a "hash table", and the fact that the wording for the columns
wasn't consistent with other functions in pgstattuple with similar
columns.

Committed with those changes.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company