Re: Legacy app not working with newer PG, is there a quick fix?

On Fri, Feb 8, 2019, 11:40 PM Lars Gustafsson <gumse(at)me(dot)com> wrote:

> I have a legacy client java application that I try to run against a new
> Postgres server.
> All data migrates as expected. Everything seems to work ok, except for one
> thing.
>
> ERROR: function to_date(timestamp without time zone, unknown) does not
> exist at character 9
> HINT: No function matches the given name and argument types. You might
> need to add explicit type casts.
>
> The application was written with and works with PG 8.2.3
>
> I understand that from PG 8.3 explicit typecasting is necessary, like:
> to_date(cast(createddate as TEXT),'YYYY-MM-DD’)
>

You could write a function say my_schema.to_date which essentially calls
and returns output of pg_catalog.to_date(cast($1 as TEXT),'YYYY-MM-DD’)

In your config change the search path to give priority to the overridding
function :

search_path=my_schema,pg_catalog

But remember that it is a bad hack and any expression index you have might
not give you a benefit or might need to be rebuilt after these changes.

> But I do not have access to the source code. Is there a way to go around
> this, by creating a macro & function to provide the type cast on the server
> side.
> Without having to change anything in the client application?
>

Yes, as said above. But there would be a cost for it on performance side.

>
> /Lars
>
>
>
> --

--

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