Re: query_id: jumble names of temp tables for better pg_stat_statement UX

> So your idea to use the relation name in eref while skipping the
> column list looks kind of promising.  Per se the attached.  Thoughts?

I feel really uneasy about this behavior becoming the default.
I can bet there are some users which run common queries across
different schemas ( e.g. multi-tenancy ) will consider this behavior a
regression
in pg_stat_statements as now all their common queries have been merged
into a single entry.

For example, I have seen users add comments to SQLs to differentiate
similar SQLs coming from different tenants. This patch makes this no longer a
somewhat decent workaround  to overcome the fact that pg_stat_statements
does not track schemas or search path.

```
select pg_stat_statements_reset();

set search_path = s1;
select /*+ user s1 */ * from foo;

set search_path = s2;
select /*+ user s2 */  * from foo;

reset search_path;
select userid, queryid, query, calls from public.pg_stat_statements;

test=# select userid, queryid, query, calls from public.pg_stat_statements;
 userid |       queryid        |               query               | calls
--------+----------------------+-----------------------------------+-------
     10 |  1788423388555345932 | select /*+ user s1 */ * from foo  |     2
     10 | -8935568138104064674 | select pg_stat_statements_reset() |     1
     10 | -8663970364987885379 | set search_path = $1              |     2
     10 | -6563543739552933350 | reset search_path                 |     1
(4 rows)
```

--
Sami Imseih
Amazon Web Services (AWS)