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

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От	Sameer Kumar
Тема	Re: Legacy app not working with newer PG, is there a quick fix?
Дата	8 февраля 2019 г. 18:46:37
Msg-id	CADp-Sm6LoNQTFe1RMFLS4atErPbW3j9LPHfuoLN2Sndy-n-=vA@mail.gmail.com обсуждение исходный текст
Ответ на	Legacy app not working with newer PG, is there a quick fix? (Lars Gustafsson <gumse@me.com>)
Список	pgsql-novice

Дерево обсуждения

On Fri, Feb 8, 2019, 11:40 PM Lars Gustafsson <gumse@me.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.