Horton

Re: explain analyze rows=%.0f

Simon Riggs <simon@2ndquadrant.com>

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From: Simon Riggs <simon@2ndQuadrant.com>
To: Ron Mayer <rm_pg@cheapcomplexdevices.com>
Cc: Euler Taveira de Oliveira <euler@timbira.com>, Robert Haas <robertmhaas@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2009-06-02T13:41:00Z
Lists: pgsql-hackers 
On Mon, 2009-06-01 at 20:30 -0700, Ron Mayer wrote:

> What I'd find strange about "6.67 rows" in your example is more that on
> the estimated rows side, it seems to imply an unrealistically precise estimate
> in the same way that "667 rows" would seem unrealistically precise to me.
> Maybe rounding to 2 significant digits would reduce confusion?

You're right that the number of significant digits already exceeds the
true accuracy of the computation. I think what Robert wants to see is
the exact value used in the calc, so the estimates can be checked more
thoroughly than is currently possible.

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support

Commits

  1. EXPLAIN: Always use two fractional digits for row counts.

  2. Adjust EXPLAIN test case to filter out "Actual Rows" values.

  3. Allow EXPLAIN to indicate fractional rows.

  4. Fix pgbench performance issue induced by commit af35fe501.