Обсуждение: select view definition from pg_views feature request

Michael Shapiro <mshapiro51@gmail.com> writes:
> It seems that the definition of a view from pg_catalog.pg_views does not
> qualify the tables used in the view if the tables are in the current search
> path.

> Is it possible to either have the definition always qualify all tables
> independent of the search_path (or else provide a new column that does
> that)?

Why don't you just change the search path to empty before selecting?

            regards, tom lane

On Sun, 03 Nov 2019 16:15:23 -0500, Tom Lane <tgl@sss.pgh.pa.us>
wrote:

>Michael Shapiro <mshapiro51@gmail.com> writes:
>> It seems that the definition of a view from pg_catalog.pg_views does not
>> qualify the tables used in the view if the tables are in the current search
>> path.
>
>> Is it possible to either have the definition always qualify all tables
>> independent of the search_path (or else provide a new column that does
>> that)?
>
>Why don't you just change the search path to empty before selecting?
>
>            regards, tom lane


I'm guessing this is fine inside a transaction, but what if you're
using a client that commits by statement?  In that case, wouldn't the
change to the path affect the other backends?

George

On Tue, 5 Nov 2019 at 11:05, George Neuner <gneuner2@comcast.net> wrote:
>
> On Sun, 03 Nov 2019 16:15:23 -0500, Tom Lane <tgl@sss.pgh.pa.us>
> >Why don't you just change the search path to empty before selecting?
>
>
> I'm guessing this is fine inside a transaction, but what if you're
> using a client that commits by statement?  In that case, wouldn't the
> change to the path affect the other backends?

See https://www.postgresql.org/docs/current/sql-set.html

"SET only affects the value used by the current session."

Also:

"The effects of SET LOCAL last only till the end of the current transaction"

Neither affects other sessions.

-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

On 11/5/19 6:43 AM, Michael Shapiro wrote:
> Can I set search_path='' (ie to a string that does not match any 
> existing schema)? Would that be the proper way to guarantee that the 
> definition for any view will always be fully-qualified?

test=# show search_path;
                            search_path
------------------------------------------------------------------
  public,accounting,history,main,utility,timeclock,table_templates

test=# select * from pg_views where viewname = 'up_view';;
  schemaname | viewname | viewowner |          definition
------------+----------+-----------+-------------------------------
  public     | up_view  | aklaver   |  SELECT up_test.id AS up_id, +
             |          |           |     up_test.col1 AS bool_col,+
             |          |           |     up_test.col_2 AS col2    +
             |          |           |    FROM up_test;
(1 row)


test=# set search_path = '';
SET
test=# show search_path;
  search_path
-------------
  ""
(1 row)

test=# select * from pg_views where viewname = 'up_view';;
  schemaname | viewname | viewowner |          definition
------------+----------+-----------+-------------------------------
  public     | up_view  | aklaver   |  SELECT up_test.id AS up_id, +
             |          |           |     up_test.col1 AS bool_col,+
             |          |           |     up_test.col_2 AS col2    +
             |          |           |    FROM public.up_test;
(1 row)

> 
> On Sun, Nov 3, 2019 at 3:15 PM Tom Lane <tgl@sss.pgh.pa.us 
> <mailto:tgl@sss.pgh.pa.us>> wrote:
> 
>     Michael Shapiro <mshapiro51@gmail.com <mailto:mshapiro51@gmail.com>>
>     writes:
>      > It seems that the definition of a view from pg_catalog.pg_views
>     does not
>      > qualify the tables used in the view if the tables are in the
>     current search
>      > path.
> 
>      > Is it possible to either have the definition always qualify all
>     tables
>      > independent of the search_path (or else provide a new column that
>     does
>      > that)?
> 
>     Why don't you just change the search path to empty before selecting?
> 
>                              regards, tom lane
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com

Adrian Klaver <adrian.klaver@aklaver.com> writes:
> On 11/5/19 6:43 AM, Michael Shapiro wrote:
>> Can I set search_path='' (ie to a string that does not match any 
>> existing schema)? Would that be the proper way to guarantee that the 
>> definition for any view will always be fully-qualified?

> [ example ]

If you read the documentation about search_path, you'll find out that
setting it to empty means that only the pg_catalog schema is present
in the effective search path (and maybe your pg_temp schema, if you
have created any temp tables).  So system catalog references,
references to built-in functions and operators, and temp table names
will not be qualified.  Everything else will be.

            regards, tom lane

On Tue, 5 Nov 2019 14:29:00 +1300, David Rowley
<david.rowley@2ndquadrant.com> wrote:


>See https://www.postgresql.org/docs/current/sql-set.html
>
>"SET only affects the value used by the current session."
>
>Also:
>
>"The effects of SET LOCAL last only till the end of the current transaction"
>
>Neither affects other sessions.


Ok, so you need to "ALTER DATABASE ..." for the change to affect
everyone.  Thanks for the clarification.

George