Re: Why Postgres doesn't use TID scan?

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От	Vladimir Ryabtsev
Тема	Re: Why Postgres doesn't use TID scan?
Дата	19 декабря 2018 г. 23:22:03
Msg-id	CAMqTPq=Pu=gS6bg2BqvZU5D=Vj4Ef1qC8wvNDEbmoMUQ7T_m6A@mail.gmail.com обсуждение исходный текст
Ответ на	Re: Why Postgres doesn't use TID scan? (Andrew Gierth <andrew@tao11.riddles.org.uk>)
Ответы	Re: Why Postgres doesn't use TID scan?
Список	pgsql-performance

> The workaround is to do it like this instead:

Strange, I tried to do like this, but the first thing came into my mind was array_agg() not array():

delete from log

where ctid = any(

select array_agg(ctid) from (

select ctid from log

where timestamp < now() at time zone 'pst' - interval '2 month'

limit 10

) v);

This query complained like this:

ERROR: operator does not exist: tid = tid[]

LINE 2: where ctid = any(

HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.

Which is strange because both array(select ...) and select array_agg() ... return the same datatype ctid[].

> But of course that's still an ugly hack.

Come on... Due to declarative nature of SQL developers sometimes need to write much dirtier and uglier hacks.

This one is just a fluffy hacky.

Vlad

В списке pgsql-performance по дате отправления:

От: Andrew Gierth
Дата: 19 декабря 2018 г., 14:41:27
Сообщение: Re: Why Postgres doesn't use TID scan?

От: Andrew Gierth
Дата: 20 декабря 2018 г., 01:23:15
Сообщение: Re: Why Postgres doesn't use TID scan?