Thread

1. Suggestion for Easier Cross-Database Query Handling in PostgreSQL

   Shivam Pandey <shivampandey91199@gmail.com> — 2026-05-15T19:00:52Z

   Hello PostgreSQL Team,
   
   I would like to share feedback from a developer perspective regarding
   cross-database querying in PostgreSQL.
   
   One feature that many developers appreciate in MySQL is the ability to
   directly query and join tables across multiple databases within the same
   server instance. This approach becomes very useful in real-world situations
   where applications need to access shared or distributed data quickly and
   efficiently.
   
   In PostgreSQL, achieving similar functionality often requires additional
   setup using extensions such as postgres_fdw or dblink. While these
   solutions are powerful and architecturally clean, they can feel complex for
   developers who are building applications rapidly or migrating from systems
   like MySQL.
   
   It would be valuable if PostgreSQL could provide a more developer-friendly
   and simplified native approach for cross-database querying while still
   maintaining PostgreSQL’s strong isolation and security principles.
   
   Possible improvements could include:
   
   1)Simpler syntax for cross-database joins
   2) Easier configuration for trusted local databases
   3) Built-in lightweight federation support
   4) Better onboarding documentation for multi-database use cases
   
   PostgreSQL is already one of the most powerful and respected databases in
   the industry. Enhancing developer convenience in this area could make
   adoption even smoother for many teams.
   
   Thank you for your incredible work and continuous innovation.
   
   Best Regards,
   Shivam Pandey
   

2. Re: Suggestion for Easier Cross-Database Query Handling in PostgreSQL

   Frank Heikens <frank@elevarq.com> — 2026-05-15T22:17:53Z

   Hi Shivam,
   
   Thank you for your feedback.
   
   One important difference is terminology.
   
   In MySQL, CREATE DATABASE and CREATE SCHEMA are essentially the same command, so what MySQL calls a “database” is effectively a schema (namespace).
   
   PostgreSQL also supports querying across schemas natively, so the same functionality is already available when the objects are in the same PostgreSQL database.
   
   In PostgreSQL, a database is a true isolation boundary with its own catalogs and connection context. Because of this design, direct joins across databases are not supported. When this is required, postgres_fdw is the recommended solution.
   
   So for most MySQL users, the equivalent approach in PostgreSQL is to use multiple schemas within a single database rather than multiple databases.
   
   Best regards,
   Frank Heikens
   
   
   
   > On May 15, 2026, at 3:06 PM, Shivam Pandey <shivampandey91199@gmail.com> wrote:
   > 
   > 
   > Hello PostgreSQL Team,
   > 
   > I would like to share feedback from a developer perspective regarding cross-database querying in PostgreSQL.
   > 
   > One feature that many developers appreciate in MySQL is the ability to directly query and join tables across multiple databases within the same server instance. This approach becomes very useful in real-world situations where applications need to access shared or distributed data quickly and efficiently.
   > 
   > In PostgreSQL, achieving similar functionality often requires additional setup using extensions such as postgres_fdw or dblink. While these solutions are powerful and architecturally clean, they can feel complex for developers who are building applications rapidly or migrating from systems like MySQL.
   > 
   > It would be valuable if PostgreSQL could provide a more developer-friendly and simplified native approach for cross-database querying while still maintaining PostgreSQL’s strong isolation and security principles.
   > 
   > Possible improvements could include:
   > 
   > 1)Simpler syntax for cross-database joins
   > 2) Easier configuration for trusted local databases
   > 3) Built-in lightweight federation support
   > 4) Better onboarding documentation for multi-database use cases
   > 
   > PostgreSQL is already one of the most powerful and respected databases in the industry. Enhancing developer convenience in this area could make adoption even smoother for many teams.
   > 
   > Thank you for your incredible work and continuous innovation.
   > 
   > Best Regards,
   > Shivam Pandey 
   

3. Re: Suggestion for Easier Cross-Database Query Handling in PostgreSQL

   Ron Johnson <ronljohnsonjr@gmail.com> — 2026-05-15T22:56:46Z

   Frank,
   
   Why doesn't the shared OID space make cross-database queries possible?  SQL
   Server does it, so the idea isn't that far-fetched.
   
   On Fri, May 15, 2026 at 6:18 PM Frank Heikens <frank@elevarq.com> wrote:
   
   >
   > Hi Shivam,
   >
   > Thank you for your feedback.
   >
   > One important difference is terminology.
   >
   > In MySQL, CREATE DATABASE and CREATE SCHEMA are essentially the same
   > command, so what MySQL calls a “database” is effectively a schema
   > (namespace).
   >
   > PostgreSQL also supports querying across schemas natively, so the same
   > functionality is already available when the objects are in the same
   > PostgreSQL database.
   >
   > In PostgreSQL, a database is a true isolation boundary with its own
   > catalogs and connection context. Because of this design, direct joins
   > across databases are not supported. When this is required, postgres_fdw is
   > the recommended solution.
   >
   > So for most MySQL users, the equivalent approach in PostgreSQL is to use
   > multiple schemas within a single database rather than multiple databases.
   >
   > Best regards,
   > Frank Heikens
   >
   >
   >
   > > On May 15, 2026, at 3:06 PM, Shivam Pandey <shivampandey91199@gmail.com>
   > wrote:
   > >
   > > 
   > > Hello PostgreSQL Team,
   > >
   > > I would like to share feedback from a developer perspective regarding
   > cross-database querying in PostgreSQL.
   > >
   > > One feature that many developers appreciate in MySQL is the ability to
   > directly query and join tables across multiple databases within the same
   > server instance. This approach becomes very useful in real-world situations
   > where applications need to access shared or distributed data quickly and
   > efficiently.
   > >
   > > In PostgreSQL, achieving similar functionality often requires additional
   > setup using extensions such as postgres_fdw or dblink. While these
   > solutions are powerful and architecturally clean, they can feel complex for
   > developers who are building applications rapidly or migrating from systems
   > like MySQL.
   > >
   > > It would be valuable if PostgreSQL could provide a more
   > developer-friendly and simplified native approach for cross-database
   > querying while still maintaining PostgreSQL’s strong isolation and security
   > principles.
   > >
   > > Possible improvements could include:
   > >
   > > 1)Simpler syntax for cross-database joins
   > > 2) Easier configuration for trusted local databases
   > > 3) Built-in lightweight federation support
   > > 4) Better onboarding documentation for multi-database use cases
   > >
   > > PostgreSQL is already one of the most powerful and respected databases
   > in the industry. Enhancing developer convenience in this area could make
   > adoption even smoother for many teams.
   > >
   > > Thank you for your incredible work and continuous innovation.
   > >
   > > Best Regards,
   > > Shivam Pandey
   >
   
   
   -- 
   Death to <Redacted>, and butter sauce.
   Don't boil me, I'm still alive.
   <Redacted> lobster!
   

4. Re: Suggestion for Easier Cross-Database Query Handling in PostgreSQL

   Tom Lane <tgl@sss.pgh.pa.us> — 2026-05-15T23:22:58Z

   Ron Johnson <ronljohnsonjr@gmail.com> writes:
   > Why doesn't the shared OID space make cross-database queries possible?
   
   OIDs are not guaranteed unique across databases.  To make this work
   transparently, we'd have to change all internal APIs to use database
   OID + object OID, not just object OID, as object identifiers.  That
   would be horrendously invasive, not to mention probably costly in
   performance (by doubling the width of cache keys, for instance).
   
   But totally independently of implementation considerations, it's not
   apparent to me that this would be a good idea.  As Frank mentioned,
   Postgres has always treated databases as isolation boundaries.
   Changing that would probably break a lot of peoples' installation
   designs.
   
   			regards, tom lane
   
   
   
   

5. Re: Suggestion for Easier Cross-Database Query Handling in PostgreSQL

   Ron Johnson <ronljohnsonjr@gmail.com> — 2026-05-15T23:57:45Z

   On Fri, May 15, 2026 at 7:22 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
   
   > Ron Johnson <ronljohnsonjr@gmail.com> writes:
   > > Why doesn't the shared OID space make cross-database queries possible?
   >
   > OIDs are not guaranteed unique across databases.
   
   
   Ah.
   
   
   > But totally independently of implementation considerations, it's not
   > apparent to me that this would be a good idea.  As Frank mentioned,
   > Postgres has always treated databases as isolation boundaries.
   > Changing that would probably break a lot of peoples' installation
   > designs.
   >
   
   Even now, roles need privilege to access databases.
   
   -- 
   Death to <Redacted>, and butter sauce.
   Don't boil me, I'm still alive.
   <Redacted> lobster!
   

6. Re: Suggestion for Easier Cross-Database Query Handling in PostgreSQL

   Isaac Morland <isaac.morland@gmail.com> — 2026-05-16T02:15:25Z

   On Fri, 15 May 2026 at 18:06, Shivam Pandey <shivampandey91199@gmail.com>
   wrote:
   
   > Hello PostgreSQL Team,
   >
   > I would like to share feedback from a developer perspective regarding
   > cross-database querying in PostgreSQL.
   >
   > One feature that many developers appreciate in MySQL is the ability to
   > directly query and join tables across multiple databases within the same
   > server instance. This approach becomes very useful in real-world situations
   > where applications need to access shared or distributed data quickly and
   > efficiently.
   >
   
   What MySQL calls databases PostgreSQL calls schemas, and PostgreSQL
   certainly has the ability to query and join tables across schemas.
   
   What MySQL might call an instance (a collection of MySQL databases)
   PostgreSQL calls a database (a collection of PostgreSQL schemas). A single
   PostgreSQL instance has the ability to host multiple databases (albeit
   sharing a single set of roles and role relationships). Can MySQL query and
   join across multiple instances?