Re: SUBSTRING performance for large BYTEA

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Tom Lane wrote:
> "Vance Maverick" <vmaverick@pgp.com> writes:
>> My question is about performance in the postgres server.  When I execute
>> "SELECT SUBSTRING (my_bytea FROM ? FOR ?) FROM my_table WHERE id =3D ?",
>> does it fetch the whole BYTEA into memory?  Or does it access only the
>> pages that contain the requested substring?
>
> Recent releases will do what you want if the column has been marked
> SET STORAGE EXTERNAL (before storing anything in it...)  See the
> ALTER TABLE reference page.

Should we consider setting storage external by default for the type?

Joshua D. Drake

>
>             regards, tom lane
>
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