Re: pgsql: doc: add namespace column to pg_buffercache example query

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(at)arbormetrix(dot)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