Re: JDBC patch for DatabaseMetaData

Hey everyone -
Go check the HACKERS archives: how schema map to PostgreSQL DB objects was
hashed out to death, more than once. As it happens, Barry's intution on
this is exactly where we ended up: a Postgresql 'database' is equivalent
to what the SQL92 standard calls a 'catalog'. Schema are essentially a
namespace within a catalog, and will be implemented as such. I know Tom
Lane hasd said that schema support is on his roadmap for early in 7.3.

How 'other' databases implement it is not controlling.

Ross Reedstrom

On Thu, Jan 10, 2002 at 03:51:06PM -0500, Paulo Merson wrote:
> I don't see a problem in the equivalence of users and schemas.
> Oracle is another database that supports schemas and the following is
> from "Oracle 9i SQL reference" manual (documentation of the "create
> schema" statement):
>
> "
> ...
> create_schema ::= CREATE SCHEMA AUTHORIZATION schema ...
> ...
> *schema*
> Specify the name of the schema. The schema name must be the same as your
> Oracle
> username.
> ...
> Note: This statement does not actually create a schema. Oracle
> automatically creates a schema when you create a user (see CREATE
> USER on page 15-29).
> ...
> "
>
>
> Paulo Merson
> Summa Technologies - www.summa-tech.com
>
> -----Original Message-----
> From: pgsql-jdbc-owner@postgresql.org
> [mailto:pgsql-jdbc-owner@postgresql.org] On Behalf Of Barry Lind
> Sent: Thursday, January 10, 2002 12:59 PM
> To: Ed Yu
> Cc: pgsql-jdbc
> Subject: Re: [JDBC] JDBC patch for DatabaseMetaData
>
>
> Ed,
>
> 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.
>
> 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.
>
> 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
>
>
>
> 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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