On 16/02/16 20:01, Tatsuo Ishii wrote:
>>> Tatsuo Ishii <ishii@postgresql.org> writes:
>>>> While reading planstats.sgml, I encounted a sentence which I don't
>>>> understand.
>>>
>>>> These numbers are current as of the last <command>VACUUM</> or
>>>> <command>ANALYZE</> on the table. The planner then fetches the
>>>> actual current number of pages in the table (this is a cheap operation,
>>>> not requiring a table scan). If that is different from
>>>> <structfield>relpages</structfield> then
>>>> <structfield>reltuples</structfield> is scaled accordingly to
>>>> arrive at a current number-of-rows estimate. In this case the value of
>>>> <structfield>relpages</structfield> is up-to-date so the rows estimate is
>>>> the same as <structfield>reltuples</structfield>.
>>>
>>>> I don't understand the last sentence (In this case...). For me it
>>>> seems it is talking about the case when replages is not different from
>>>> what the planner fetches from the table. If so, why "In this case"?
>>>
>>> I think what it meant is "In the example above, ...". Feel free to
>>> change it if you think that is clearer.
>>
>> Oh, I see. I'm going to change "In this case" to "In the example above".
>
> Done.
>
Yeah, that is clearer.