Re: Non-text EXPLAIN output for partial aggregation

On Sun, Jun 26, 2016 at 4:25 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I noticed that the EXPLAIN code is set up so that in non-text output
> modes, you get output like this for partial-aggregate plans:
>
>        "Node Type": "Aggregate",                  +
>        "Strategy": "Plain",                       +
>        "Operation": "Finalize",                   +
> ...
>                "Node Type": "Aggregate",          +
>                "Strategy": "Plain",               +
>                "Operation": "Partial",            +
>
> That is, the "Operation" field type has been commandeered to indicate
> partial-aggregation cases.  This seems like a pretty bad idea to me,
> for two reasons:
>
> 1.  In other plan node types, "Operation" refers to SQL-visible semantics,
> in fact always Select/Insert/Update/Delete.  Re-using it for an
> implementation detail doesn't seem very consistent.
>
> 2.  As coded, the field is not printed at all for a non-partial aggregate
> node.  This is just wrong.  A given node type should have a fixed set of
> attributes.
>
> I think we should use some other field name, maybe "Step" or
> "PartialMode", and have "Simple" or "Plain" as the default field
> contents.  It's also arguable that this field should distinguish all the
> values of the AggSplit enum we just invented, though I'm not sure how
> important it is to report serialization options.  I'm not wedded to any
> particular ideas here, other than that omitting the field in the simple
> case is bad.
>
> Comments, naming ideas?

Simple sounds better than Plain, as between the two of them, because
Plain already means something with respect to aggregates.

-- 
Robert Haas
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