Re: Btree Index on PostgreSQL and Wiredtiger (MongoDB3.2)

After examining the benchmark design - I see we are probably not being helped by the repeated insertion of keys all of form 'userxxxxxxx' leading to some page splitting.

However your index rebuild gets you from 5 to 3 GB - does that really help performance significantly?

regards

Mark

On 11/08/16 16:08, Kisung Kim wrote:

Thank you for your information.
Here is the result:

After insertions:

ycsb=# select * from pgstatindex('usertable_pkey');
 version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation
---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
       2 |          3 | 5488721920 |         44337 |     4464 |     665545 |           0 |             0 |       52 |                 11
(1 row)

After rebuild:


ycsb=# select * from pgstatindex('usertable_pkey');
 version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation
---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
       2 |          3 | 3154296832 |         41827 |         1899 |     383146 |           0 |             0 |            90.08 |                  0


It seems like that rebuild has an effect to reduce the number of internal and leaf_pages and make more dense leaf pages.