Robert Haas <robertmhaas@gmail.com> wrote:
> On Thu, Dec 10, 2009 at 10:52 AM, Greg Smith <greg@2ndquadrant.com> wrote:
> >> I don't think IO is a terrible name for an option but I like BUFFERS
> >> better. ?I don't think the BUFFERS/BLOCKS confusion is too bad, but
> >> perhaps we could use BUFFERS in both places.
> >
> > I don't know how "blocks" got into here in the first place--this concept is
> > "buffers" just about everywhere else already, right?
>
> I think we have some places already in the system where we bounce back
> and forth between those terms. I expect that's the reason.
The "blocks" comes from pg_statio_all_tables.heap_blks_{read|hit},
but "buffers" might be easy to understand. One matter for concern
is that "buffer read" might not be clear whether it is a memory access
or a disk read.
Anyway, a revised patch according to the comments is attached.
The new text format is:
Buffers: shared hit=675 read=968, temp read=1443 written=1443
* Zero values are omitted. (Non-text formats could have zero values.)
* Rename "Blocks:" to "Buffers:".
* Remove parentheses and add a comma between shared, local and temp.
=# EXPLAIN (BUFFERS, ANALYZE) SELECT *
FROM pgbench_accounts a, pgbench_branches b
WHERE a.bid = b.bid AND abalance >= 0 ORDER BY abalance;
QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------
Sort (cost=54151.83..54401.83 rows=100000 width=461) (actual time=92.551..109.646 rows=100000 loops=1)
Sort Key: a.abalance
Sort Method: external sort Disk: 11544kB
Buffers: shared hit=675 read=968, temp read=1443 written=1443
-> Nested Loop (cost=0.00..4141.01 rows=100000 width=461) (actual time=0.048..42.190 rows=100000 loops=1)
Join Filter: (a.bid = b.bid)
Buffers: shared hit=673 read=968
-> Seq Scan on pgbench_branches b (cost=0.00..1.01 rows=1 width=364) (actual time=0.003..0.004 rows=1
loops=1)
Buffers: shared hit=1
-> Seq Scan on pgbench_accounts a (cost=0.00..2890.00 rows=100000 width=97) (actual time=0.038..22.912
rows=100000loops=1)
Filter: (a.abalance >= 0)
Buffers: shared hit=672 read=968
Total runtime: 116.058 ms
(13 rows)
Regards,
---
Takahiro Itagaki
NTT Open Source Software Center
