Re: WIP: explain analyze with 'rows' but not timing

2011/12/22 Tomas Vondra <tv(at)fuzzy(dot)cz>:
> The gettimeofday() calls are not exactly cheap in some cases, so why to
> pay that price when all you need is the number of rows?

Fair point.

> The patch attached does this:
>
> 1) adds INSTRUMENT_ROWS, a new InstrumentOption
>
>   - counts rows without timing (no gettimeofday() callse)
>   - if you want timing info, use INSTRUMENT_TIMER
>
> 2) adds new option "TIMING" to EXPLAIN, i.e.
>
>    EXPLAIN (ANALYZE ON, TIMING ON) SELECT ...
>
> 3) adds auto_explain.log_rows_only (false by default)
>
>   - if you set this to 'true', then the instrumentation will just
>     count rows, without calling gettimeofday()

This seems like an unnecessarily confusing interface, because you've
named the auto_explain option differently from the EXPLAIN option and
given it (almost) the opposite sense: timing=off means the same thing
as log_rows_only=on.

I think the EXPLAIN (TIMING) option is good the way you have it, but
then just have auto_explain.log_timing, with a default value of on.

--
Robert Haas
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