Re: explain and PARAM_EXEC

The patch I sent earlier is flaud with respect to subplan parameter 
numbering, I counted from zero where the parParam list had to be used.

Yeb Havinga wrote: 
> See patch below against HEAD.
>
> Example of query against catalog:
>
> postgres=# explain verbose select oid::int + 1,(select oid from 
> pg_class a where a.oid = b.relfilenode and a.relnamespace = 
> b.relnamespace) from pg_class b;
>                                               QUERY 
> PLAN                                              
> -------------------------------------------------------------------------------------------------------- 
>
> Seq Scan on pg_catalog.pg_class b  (cost=0.00..2459.64 rows=296 width=12)
>   Output: ((b.oid)::integer + 1), SubPlan 1 ($0 := b.relfilenode, $1 
> := b.relnamespace)
>   SubPlan 1
>     ->  Index Scan using pg_class_oid_index on pg_catalog.pg_class a  
> (cost=0.00..8.27 rows=1 width=4)
>           Output: a.oid
>           Index Cond: (a.oid = $0)
>           Filter: (a.relnamespace = $1)
> (7 rows)
>
> Explain of alternative subplan (query comes from aggregates.sql in 
> regression).
>
> regression=# explain verbose select ten, sum(distinct four) from onek a
> group by ten
> having exists (select 1 from onek b where sum(distinct a.four) = b.four);
>                                      QUERY 
> PLAN                                     
> -------------------------------------------------------------------------------------- 
>
> GroupAggregate  (cost=197.83..216.52 rows=10 width=8)
>   Output: a.ten, sum(DISTINCT a.four)
>   Filter: (alternatives: SubPlan 1 ($0 := sum(DISTINCT a.four)) or 
> hashed SubPlan 2)
>   ->  Sort  (cost=197.83..200.33 rows=1000 width=8)
>         Output: a.ten, a.four
>         Sort Key: a.ten
>         ->  Seq Scan on public.onek a  (cost=0.00..148.00 rows=1000 
> width=8)
>               Output: a.ten, a.four
>   SubPlan 1
>     ->  Seq Scan on public.onek b  (cost=0.00..150.50 rows=250 width=0)
>           Filter: ($0 = b.four)
>   SubPlan 2
>     ->  Seq Scan on public.onek b  (cost=0.00..148.00 rows=1000 width=4)
>           Output: b.four
> (14 rows)
>
> Would the explain above be better if the filter with subplans 
> arguments showed the EXISTS keyword? Much code from get_sublink_expr 
> could be reused to show additional info depending on the sublink type 
> and testexpr.
>
> Other info: there are now only appends to the context->buf. The 
> problems with OUTER var I mentioned earlier are gone now arguments are 
> deparsed using get_rule_expr instead of deparse_expression.
>
> regards,
> Yeb Havinga
>