On Mon, Jan 13, 2020 at 09:12:38PM +0100, Julien Rouhaud wrote:
>On Mon, Jan 13, 2020 at 05:32:53PM +0100, Tomas Vondra wrote:
>> On Mon, Jan 13, 2020 at 11:08:40AM +0300, Konstantin Knizhnik wrote:
>> >
>> >"if any code tried to access the statistics directly from the table,
>> >rather than via the caches".
>> >
>> >Currently optimizer is accessing statistic though caches. So this
>> >approach works. If somebody will rewrite optimizer or provide own
>> >custom optimizer in extension which access statistic directly
>> >then it we really be a problem. But I wonder why bypassing catalog
>> >cache may be needed.
>> >
>>
>> I don't know, but it seems extensions like hypopg do it.
>
>AFAIR, hypopg only opens pg_statistic to use its tupledesc when creating
>statistics on hypothetical partitions, but it should otherwise never reads or
>need plain pg_statistic rows.
Ah, OK! Thanks for the clarification. I knew it does something with the
catalog, didn't realize it only gets the descriptor.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
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