Re: pgstattuple extension for indexes

Hi folks,

As I said on -PATCHES, I've been working on an utility to get
a b-tree index information. I'm happy to introduce
my new functions to you.

pgstattuple module provides a `pgstatindex()`, and other small
functions, which allow you to get b-tree internal information.
I believe this module will be helpful to know b-tree index deeply.

So please try it, send comment to me, and have fun.

Thanks,
--
NAGAYASU Satoshi <nagayasus(at)nttdata(dot)co(dot)jp>

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pgbench=# \x
Expanded display is on.
pgbench=# SELECT * FROM pgstatindex('accounts_pkey');
-[ RECORD 1 ]------+--------
version | 2
tree_level | 1
index_size | 3588096
root_block_no | 3
internal_pages | 0
leaf_pages | 437
empty_pages | 0
deleted_pages | 0
avg_leaf_density | 59.5
leaf_fragmentation | 49.89
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