Re: Should PG backend know how to represent metadata?

At 02:43 17/07/00 -0400, Tom Lane wrote:
>That is a
>substantial advantage, but you only get it if you make sure the backend
>display capability is defined in a way that lets all these apps use it.
>That might take some careful thought. For example, does the definition
>of a table include associated constraints and indexes?

You need to separate the API from what is displayed (eg. in psql).

Suggestion:

I would envisage the API consisting of a custom dump routine for each
object type. In the case of the table dumper API, it would return a table
definition with no indexes or constraints and a list of related entities
consisting of (object-type, object-oid) pairs suitable for passing back to
the dumper API. psql could display as little or as much as it desired,
pg_dump could ferret the extra items away for later use etc. For those
items that can not be separated out, then they obviously have to go into
the main definition.

>Also, psql's \d command
>doesn't display the schema of a table in the form of a CREATE command
>to recreate it, and I don't think it should.

I agree. \D is not to replace \d or \df etc.

>Certainly you don't want
>to condemn every app that wants to know "what are the columns of this
>table"

This is where we need to decide what the dumper code is for. I don't know
much about the other things you have mentioned, so perhaps you could
expand. But, in my original plan, this suggestion was intended for human
readable dumps from pg_dump and psql. It would be great if it could be made
to work elsewhere.

> to have to include a full SQL parser to make sense of the
>answer. So I think some thought is needed to figure out what a
>general-purpose representation would be like.

And where it would go...

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