Re: JDBC patch for DatabaseMetaData - Mailing list pgsql-jdbc

> You stated that "I prefer to have a working JDBC driver now than a
> compliance driver in the future."  I agree with this statement, but I
> don't view making scheam = user as working.  That IMHO is introducing a
> bug and does not result in a "working" set of functionality.  Also it
> has the problem that when schema support is added in the future then
> there will need to be a non-backwardly compatible change in the behavior
> of the driver.
>

I agree with that. For MSSQL 7.0 server, schema is not the user. In some of
the replies to this thread, Peter Eisentraut <peter_e@gmx.net> message
contains a statement "Entry Level SQL92, schema names *must* be equal to the
name of the user that creates/owns it" that I was not able to find in the
SQL92 specification. And I have no intention to create a bug that is no
backwardly compatible.

> The jdbc spec was written taking into account that different databases
> have different functionality.  That is why the DatabaseMetaData class
> exists, to tell a client what functionality is supported by the server.
>   The postgres jdbc driver correctly states in the metadata class that
> it does not support schemas.  Therefore any jdbc compliant client should
> not expect schema support.
>

I also concur on the fact that if the jdbc driver correctly states that in
the DatabaseMetadata class, schema is not support, the driver should not use
anything related to schema.

But I have a delima here. I need to use DatabaseMetaData.getTables(...) to
return me all tables that I have access to. Currently, like psql, the jdbc
driver returns the entire list of tables exists in the database whether or
not I have access to them.

Unfortunately, the jdbc driver does not have any other methods for me to
determine if I have access to the tables/views causes my classes to throw an
exception because it is returned in the ResultSet from calling
DatabaseMetaData.getTables() and I do not have select privilege to those
tables/views. The only way out for me (or at least I think) is to:

    a) do what I did assuming username is equivalent to schema (which I
agree is bad),
    b) re-state the sql query for DatabaseMetaData.getTables() to return me
only tables/views that I have access to.

I can see your point that I should not pick option "a" so I'm seriously
considering option "b".

May be you can help me with this, the problem I have is that the column
'pg_class.relacl' is an array. I simply don't know how to extract out the
array elements such as "=r" (public select) and "username=arwR" (hack, I
don't even know the exact format of this column relacl!) and perform a
comparison to the username so that the getTables() returns only tables/views
that I have access to.

So any input is appreciated!

> Your original patch has some good fixes in it, but I won't apply it as
> is because of the concerns I have raised about the schema stuff.  Can
> you resubmit the patch without the schema changes?
>
> thanks,
> --Barry
>
>

Thanks, I'll resubmit the patch once I got a chance.

>
> Ed Yu wrote:
>
> > You are right on that user != schema. But I would rather have a
functional
> > driver now than an compliance driver way down in the future.
> >
> > As I can recall, the only database I've worked with that supports schema
is
> > UDB (DB2). Schema is a label that groups database objects together. It
is
> > functionally equivalent to a user except that login is not permitted for
a
> > schema (in the context of security/permission granting).
> >
> > Since Postgresql has the concept of a database, it would be equalvalent
to
> > the concept of catalog and user would be functionally equalvalent to
schema.
> >
> > Again, I prefer to have a working JDBC driver now than a compliance
driver
> > in the future.
> >
> > What do you think guys?
> >
> > ----- Original Message -----
> > From: "Barry Lind" <barry@xythos.com>
> > To: "Ed Yu" <ekyu@sc.rr.com>
> > Cc: "pgsql-jdbc" <pgsql-jdbc@postgresql.org>
> > Sent: Monday, January 07, 2002 12:44 PM
> > Subject: Re: JDBC patch for DatabaseMetaData
> >
> >
> >
> >>It appears that this patch is trying to add schema support for the
> >>getTables method.  But since postgres doesn't yet support schemas
> >>(perhaps in 7.3), I don't see how this is going to be possible.  I
> >>certainly don't agree with the approach here that user = schema.  That
> >>may be how Oracle does it, but certainly isn't how the ANSI standard
> >>defines schemas.
> >>
> >>thanks,
> >>--Barry
> >>
> >>Ed Yu wrote:
> >>
> >>
> >>>The following patches up the DatabaseMetaData.getTables() method:
> >>>
> >>>1638c1638,1641
> >>><     if(tableNamePattern==null)
> >>>---
> >>>
> >>>
> >>>>   if((schemaPattern==null) || (schemaPattern.length()==0))
> >>>>     schemaPattern="%";
> >>>>
> >>>>   if((tableNamePattern==null) || (tableNamePattern.length()==0))
> >>>>
> >>>>
> >>>1653c1656,1657
> >>><     StringBuffer sql = new StringBuffer("select relname,oid,relkind
> >>>
> > from
> >
> >>>pg_class where (");
> >>>---
> >>>
> >>>
> >>>>   StringBuffer sql = new StringBuffer(
> >>>>       "select relname,pg_class.oid,relkind from pg_class, pg_user
> >>>>
> > where
> >
> >>>(");
> >>>1665a1670
> >>>
> >>>
> >>>>   // Modified by Ed Yu <ekyu@asgnet.psc.sc.edu>
> >>>>
> >>>1667,1669c1672,1678
> >>><     sql.append(") and relname like '");
> >>><     sql.append(tableNamePattern.toLowerCase());
> >>><     sql.append("'");
> >>>---
> >>>
> >>>
> >>>>   sql.append(") and relname");
> >>>>   if ((tableNamePattern.indexOf("%") >= 0) ||
> >>>>           (tableNamePattern.indexOf("_") >= 0))
> >>>>       sql.append(" like ");
> >>>>   else
> >>>>       sql.append(" = ");
> >>>>   sql.append("'" + tableNamePattern.toLowerCase() + "'");
> >>>>
> >>>>
> >>>1670a1680,1690
> >>>
> >>>
> >>>>   // Added by Ed Yu <ekyu@asgnet.psc.sc.edu>
> >>>>   // Now take the schemaPattern into account
> >>>>   sql.append(" and pg_class.relowner = pg_user.usesysid");
> >>>>   sql.append(" and pg_user.usename");
> >>>>   if ((schemaPattern.indexOf("%") >= 0) ||
> >>>>           (schemaPattern.indexOf("_") >= 0))
> >>>>       sql.append(" like ");
> >>>>   else
> >>>>       sql.append(" = ");
> >>>>   sql.append("'" + schemaPattern + "'");
> >>>>
> >>>>
> >>>>
> >>>1688a1709,1710
> >>>
> >>>
> >>>>// JDBC definition for TABLE_TYPE - "TABLE", "VIEW", "SYSTEM TABLE",
> >>>>// "GLOBAL TEMPORARY", "LOCAL TEMPORARY", "ALIAS", "SYNONYM".
> >>>>
> >>>>
> >>>1699a1722,1724
> >>>
> >>>
> >>>>case 'v':
> >>>>           relKind = "VIEW";
> >>>>           break;
> >>>>
> >>>>
> >>>1707c1732,1740
> >>><  tuple[3] = relKind.getBytes(); // Table type
> >>>---
> >>>
> >>>
> >>>>       // Added by Ed Yu <ekyu@asgnet.psc.sc.edu>
> >>>>// Fix NullPointerException if return type is not handled in the
> >>>>// above switch statement.
> >>>>if (relKind==null)
> >>>> tuple[3] = null;
> >>>>else
> >>>> tuple[3] = relKind.getBytes(); // Table type
> >>>>
> >>>>
> >>>>
> >>>
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> >>
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>
>
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