Re: cursor with hold must be save to disk?

the Postgresql version is 13.6
and the DECLARE COMMAND IS

declare sdx_3a6c_8 no scroll binary cursor without hold for select
"roalkL"."smid","roalkL"."smgeometry" from "public"."roalkL" where
"roalkL"."smgeometry" &&
st_makeenvelope(321673.3153346270555630,3375950.6560412631370127,367212.1915803211741149,3402758.1912380573339760,32649)

the data might be 1GB,and we need get all in about 10 seconds.

Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> 于2023年4月14日周五 23:11写道：

> On 4/14/23 04:04, 黄宁 wrote:
> > i want to use cursor with hold ,but when I declare a curosr , it takes a
> > long time to save the result set to disk. can i save the query state in
> > memory? and fetch forward the next result.
> >
>
> From the docs:
>
> https://www.postgresql.org/docs/current/sql-declare.html
>
> A cursor created with WITH HOLD is closed when an explicit CLOSE command
> is issued on it, or the session ends. In the current implementation, the
> rows represented by a held cursor are copied into a temporary file or
> memory area so that they remain available for subsequent transactions.
>
> So I am going to guess the cursor query is holding a large amount of data.
>
> To get a more specific answer you will need to provide:
>
> 1) Postgres version.
>
> 2) The complete DECLARE command being used.
>
> 3) An indication of the amount of data being retrieved.
>
> 4) The actual time for a 'long time'.
>
> --
> Adrian Klaver
> adrian(dot)klaver(at)aklaver(dot)com
>
>