Re: GUC flags

On Wed, Jan 05, 2022 at 05:55:17PM -0600, Justin Pryzby wrote:
> pg_settings is currently defined with "SELECT *". Is it fine to enumerate a
> list of columns instead ?

I'd like to think that this is a better practice when it comes
documenting the columns, but I don't see an actual need for this extra
complication here.

> + initStringInfo(&ret);
> + appendStringInfoChar(&ret, '{');
> +
> + if (flags & GUC_NO_SHOW_ALL)
> + appendStringInfo(&ret, "NO_SHOW_ALL,");
> + if (flags & GUC_NO_RESET_ALL)
> + appendStringInfo(&ret, "NO_RESET_ALL,");
> + if (flags & GUC_NOT_IN_SAMPLE)
> + appendStringInfo(&ret, "NOT_IN_SAMPLE,");
> + if (flags & GUC_EXPLAIN)
> + appendStringInfo(&ret, "EXPLAIN,");
> + if (flags & GUC_RUNTIME_COMPUTED)
> + appendStringInfo(&ret, "RUNTIME_COMPUTED,");
> +
> + /* Remove trailing comma, if any */
> + if (ret.len > 1)
> + ret.data[--ret.len] = '\0';

The way of building the text array is incorrect here. See
heap_tuple_infomask_flags() in pageinspect as an example with all the
HEAP_* flags. I think that you should allocate an array of Datums,
use CStringGetTextDatum() to assign each array element, wrapping the
whole with construct_array() to build the final value for the
parameter tuple.
--
Michael