Re: Buffer usage in EXPLAIN and pg_stat_statements (review)

Here is an update version of buffer usage patch.
  * All buffers_* and bufs_* are renamed to blks_*.
  * 'disc' => 'disk' in documentation
  * Replace debug-log to Assert().
  * Fix a bug in ResetLocalBufferUsage(). log_xxx_stats had not worked.

Robert Haas <robertmhaas@gmail.com> wrote:

> > ?* Can I use "temp" instead of "Temp Read" to shorten the name?
> I can't tell what that means without reading the source code.  I think
> clarity should take precedence over brevity.

I used temp_blks_read because we have idx_blks_read in pg_statio_xxx.


=# \d pg_stat_statements
       View "public.pg_stat_statements"
     Column     |       Type       | Modifiers
----------------+------------------+-----------
 userid         | oid              |
 dbid           | oid              |
 query          | text             |
 calls          | bigint           |
 total_time     | double precision |
 rows           | bigint           |
 blks_hit       | bigint           |
 blks_read      | bigint           |
 temp_blks_read | bigint           |

=# SET work_mem = '1MB';
=# EXPLAIN (ANALYZE, BUFFERS) SELECT * FROM pgbench_accounts ORDER BY bid;
                                                          QUERY PLAN

-------------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=21913.32..22163.33 rows=100005 width=97) (actual time=81.345..99.054 rows=100000 loops=1)
   Sort Key: bid
   Sort Method:  external sort  Disk: 10472kB
   Blocks Hit: 0  Read: 0  Temp Read: 1309
   ->  Seq Scan on pgbench_accounts  (cost=0.00..2667.05 rows=100005 width=97) (actual time=0.018..23.129 rows=100000
loops=1)
         Blocks Hit: 74  Read: 1694  Temp Read: 0
 Total runtime: 105.238 ms
(7 rows)

=# SET work_mem = '18MB';
=# EXPLAIN (ANALYZE, BUFFERS) SELECT * FROM pgbench_accounts ORDER BY bid;
                                                          QUERY PLAN

-------------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=10972.32..11222.33 rows=100005 width=97) (actual time=35.437..43.069 rows=100000 loops=1)
   Sort Key: bid
   Sort Method:  quicksort  Memory: 17916kB
   Blocks Hit: 0  Read: 0  Temp Read: 0
   ->  Seq Scan on pgbench_accounts  (cost=0.00..2667.05 rows=100005 width=97) (actual time=0.028..15.030 rows=100000
loops=1)
         Blocks Hit: 32  Read: 1635  Temp Read: 0
 Total runtime: 52.026 ms
(7 rows)


Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center