Re: [HACKERS] Small improvement to parallel query docs

On 14 February 2017 at 09:21, Robert Haas <robertmhaas@gmail.com> wrote:
> On Sun, Feb 12, 2017 at 7:16 PM, David Rowley
> -    table. Each worker will execute the outer side of the plan in full, which
> -    is why merge joins are not supported here. The outer side of a merge join
> -    will often involve sorting the entire inner table; even if it involves an
> -    index, it is unlikely to be productive to have multiple processes each
> -    conduct a full index scan of the inner table.
> +    relation. Each worker will execute the inner side of the join in full,
> +    which is why merge joins are not supported here. The inner side of a merge
> +    join will often involve sorting the entire inner relation; even if it
> +    involves an index, it is unlikely to be productive to have multiple
> +    processes each conduct a full index scan of the inner side of the join.
>
> Why s/table/relation/?  I don't think that's useful, especially
> because the first part of that very same paragraph would still say
> "table".

Perhaps it's not correct to do that. I did mean relation is the true
relational theory sense, rather than where relkind = 'r'. I didn't
really like the way it assumed the inner side was a table. Perhaps its
better to just say "involve sorting the entire inner side of the join"



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