Re: pgsql: doc: add namespace column to pg_buffercache example query - Mailing list pgsql-committers

On 2020-03-31 23:16, Bruce Momjian wrote:
> doc:  add namespace column to pg_buffercache example query
> 
> Without the namespace, the table name could be ambiguous.
> 
> Reported-by: adunham@arbormetrix.com
> 
> Discussion: https://postgr.es/m/158155175140.23798.2189464781144503491@wrigleys.postgresql.org
> 
> Backpatch-through: 9.5

  <screen>
-regression=# SELECT c.relname, count(*) AS buffers
+regression=# SELECT n.nspname, c.relname, count(*) AS buffers
               FROM pg_buffercache b INNER JOIN pg_class c
               ON b.relfilenode = pg_relation_filenode(c.oid) AND
                  b.reldatabase IN (0, (SELECT oid FROM pg_database
                                        WHERE datname = current_database()))
-             GROUP BY c.relname
-             ORDER BY 2 DESC
+             JOIN pg_namespace n ON n.oid = c.relnamespace
+             GROUP BY n.nspname, c.relname
+             ORDER BY 3 DESC
               LIMIT 10;

Seems kind of confusing to use INNER JOIN once and then JOIN the other time.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services