Re: GIN pageinspect functions

On Tue, Oct 7, 2014 at 10:33 PM, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
wrote:
>
> Some time ago, when debugging a GIN bug, I wrote these pageinspect
functions to inspect GIN indexes. They were very useful; we should add them.
>

I think these functions will be quite useful for debugging purpose
and we already have similar function's for other index (btree).

Few suggestions for patch:

1. Documentation seems to be missing, other API's exposed
via pageinspect are documented at:
http://www.postgresql.org/docs/devel/static/pageinspect.html

2.
+CREATE FUNCTION gin_metapage(IN page bytea,
+ OUT pending_head bigint,
+ OUT pending_tail bigint,
+
OUT tail_free_size int4,
+ OUT n_pending_pages bigint,
+ OUT n_pending_tuples bigint,
+ OUT
n_total_pages bigint,
+ OUT n_entry_pages bigint,
+ OUT n_data_pages bigint,
+ OUT n_entries bigint,
+
OUT version int4)
+AS 'MODULE_PATHNAME', 'gin_metapage'
+LANGUAGE C STRICT;

a. Isn't it better to name the function as gin_metap(..) similar to
existing function bt_metap(..)?
b. Can this function have a similar signature as bt_metap() which means
it should take input as relname?

3. Can gin_dataleafpage() API have similar name and signature as
API bt_page_items() exposed for btree?

4. Can we have any better name for gin_pageopaq (other API name's
in this module are self explanatory)?

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com