Re: optimize pg_tables query ( text vs varchar ) ...why ?

On 2017-08-16 14:41, gmb wrote:
> Hi
> For DDL purposes we make significant use of pg_catalog tables/views.
> Were investigating performance issues in a typical function:
>
> CREATE FUNCTION tableexists( s TEXT , t TEXT ) returns boolean as
> $$
> SELECT count(tablename) = 1 FROM pg_tables WHERE schemaname=$1 and
> tablename=$2;
> $$
> language sql
>
> When change the params of above function to VARCHAR (instead of TEXT),
> performance improved dramatically.
> We then changed params to NAME ( as per pg_tables column type ) , but
> the
> performance stayed more or less the same.
>
> Can somebody explain this to me ? Is there a better way in which to
> handle
> these ?
> (This will be implemented on most object in the catalog e.g. columns,
> sequences, functions, etc )
>
> Regards
> gmb
>
>
>
> --
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> Sent from the PostgreSQL - general mailing list archive at Nabble.com.

A wild stab in the dark: typecasting?
pg_tables returns 'name' type, not TEXT, so some sort of transformation
has to be done and that takestime.