From: Takahiro Itagaki <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
To: Greg Smith <greg(at)2ndquadrant(dot)com>
Cc: Euler Taveira de Oliveira <euler(at)timbira(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org>
Date: 2009-12-09 05:36:51
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Greg Smith <greg(at)2ndquadrant(dot)com> wrote:

> I just executed that. Note that there are two bits of subjective
> tweaking possible to do with this one when it's committed: slimming
> down the width of the display, and Euler's suggestion's for rewording.
> I linked to both of those messages in the CF app, labeled as notes the
> committer might want to consider, but that the patch hasn't been updated
> to include yet.

Sure, I should have merge all of the comments. Patch attached.

- Updated documentation as Euler's suggestion, but I replaced
the "It" of the second last sentence to "This parameter".
- Updated the output format as follows. I think this format is the most
similar to existing lines. ("actual" by ANALYZE and "Filter:").

Note that the patch also removes buffer counters from log_statement_stats,
but we only have brief descriptions about the options. Our documentation
say nothing about buffer counters, so I didn't modify those lines in sgml.
IMHO, we could remove those options completely because we can use
EXPLAIN BUFFERS and DTrace probes instead of them.

FROM pgbench_accounts a, pgbench_branches b
WHERE = AND abalance > 0 ORDER BY abalance;
Sort (cost=2891.03..2891.04 rows=1 width=461) (actual time=22.494..22.494 rows=0 loops=1)
Sort Key: a.abalance
Sort Method: quicksort Memory: 25kB
Blocks: (shared hit=96 read=1544 written=0) (local hit=0 read=0 written=0) (temp read=0 written=0)
-> Nested Loop (cost=0.00..2891.02 rows=1 width=461) (actual time=22.488..22.488 rows=0 loops=1)
Join Filter: ( =
Blocks: (shared hit=96 read=1544 written=0) (local hit=0 read=0 written=0) (temp read=0 written=0)
-> Seq Scan on pgbench_accounts a (cost=0.00..2890.00 rows=1 width=97) (actual time=22.486..22.486 rows=0 loops=1)
Filter: (abalance > 0)
Blocks: (shared hit=96 read=1544 written=0) (local hit=0 read=0 written=0) (temp read=0 written=0)
-> Seq Scan on pgbench_branches b (cost=0.00..1.01 rows=1 width=364) (never executed)
Blocks: (shared hit=0 read=0 written=0) (local hit=0 read=0 written=0) (temp read=0 written=0)
Total runtime: 22.546 ms
(13 rows)

Takahiro Itagaki
NTT Open Source Software Center

Attachment Content-Type Size
explain_buffers_20091209.patch application/octet-stream 20.7 KB

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