Implementation of external data management #1158

[paradox1307]

Link to RFC - Distributed queries (Management of External Data) proposal

[paradox1307]

This is a draft implementation of external data management (SQL:MED). It will be improved after the metacache #7954 is merged.

[sim1984]

Are there any restrictions for users/roles on using foreign servers? I think there should be. That is, we should have something like:

GRANT USAGE ON SERVER <server_name>
TO <grantee_list> [WITH GRANT OPTION]
[{GRANTED BY | AS} [USER] <grantor>];

REVOKE [GRANT OPTION FOR]
USAGE ON SERVER <server_name>
FROM <grantee_list>
[{GRANTED BY | AS} [USER] <grantor>];

This is important, especially if the foreign server stores authentication data. Not every authenticated user should be able to use it in an EXECUTE STATEMENT.

[sim1984]

May be RDB$FOREIGN_OPTION_TYPE ?

[paradox1307]

Yes, corrected.

[sim1984]

Why is there a semicolon ; here? I would have expected an equals symbol =.

[paradox1307]

The idea was that option names and option values follow each other and there is no sense in adding a special character to separate them, i.e. option_1_name;option_1_value;option_2_name;option_2_value;.... If this is confusing, it can be changed to something else.

[sim1984]

In principle, this approach will work, provided that each option requires a value. In this case, we eliminate the possibility of passing only the option name as a flag.

[paradox1307]

Are there any restrictions for users/roles on using foreign servers? I think there should be.

Yes, there should be restrictions on using foreign servers. The MED standard requires GRANT/REVOKE USAGE ON FOREIGN SERVER. Implemented in df133b1 . Please note that when creating foreign tables and user mappings, USAGE checks have also been added, as required by the standard.

[sim1984]

This description confuses people because it's unclear what's required and what's optional. A better explanation would be:

ALTER SERVER <foreign server name>
        [[DROP] {FOREIGN DATA WRAPPER | USING PLUGIN} <provider(plugin)>] 
        [OPTIONS (<option> [, <option> ...] )]

<option> ::= {
          <option name> = 'value'
        | <option name> [{FILE | ENV}] 'value' 
        | DROP <option name>
}

[sim1984]

Are there any restrictions for users/roles on using foreign servers? I think there should be.

Yes, there should be restrictions on using foreign servers. The MED standard requires GRANT/REVOKE USAGE ON FOREIGN SERVER. Implemented in df133b1 . Please note that when creating foreign tables and user mappings, USAGE checks have also been added, as required by the standard.

This should be described in the README.MED.md documentation.