Re: Don't deform column-by-column in composite_to_json

On 2019-Feb-01, Andres Freund wrote:

> diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
> index de0d0723b71..8724022df54 100644
> --- a/src/backend/utils/adt/json.c
> +++ b/src/backend/utils/adt/json.c
> @@ -1755,6 +1755,8 @@ composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
>      int            i;
>      bool        needsep = false;
>      const char *sep;
> +    Datum        values[MaxHeapAttributeNumber];
> +    bool        nulls[MaxHeapAttributeNumber];
>  
>      sep = use_line_feeds ? ",\n " : ",";

Isn't this putting much more than needed in the stack?  Seems like we
could just allocate tupdesc->natts members dynamically.  Not sure if we
care: it's about 12 kB; maybe considering palloc overhead, using the
stack is better.

Worth asking.  But if this is worth doing here, then it's worth doing in
a lot more places, isn't it?

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
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