Re: Add sub-transaction overflow status in pg_stat_activity

> + <entry role="catalog_table_entry"><para role="column_definition">
> + <structfield>subxact_count</structfield> <type>xid</type>
> + </para>
> + <para>
> + The current backend's active subtransactions count.

subtransaction (no s)

> + Set to true if current backend's subtransaction cache is overflowed.

Say "has overflowed"

> + if (local_beentry->subxact_count > 0)
> + {
> + values[30] = local_beentry->subxact_count;
> + values[31] = local_beentry->subxact_overflowed;
> + }
> + else
> + {
> + nulls[30] = true;
> + nulls[31] = true;
> + }

Why is the subxact count set to NULL instead of zero ?

You added this to pg_stat_activity, which already has a lot of fields.
We talked a few months ago about not adding more fields that weren't commonly
used.
https://www.postgresql.org/message-id/flat/20210426191811.sp3o77doinphyjhu%40alap3.anarazel.de#d96d0a116f0344301eead2676ea65b2e

Since I think this field is usually not interesting to most users of
pg_stat_activity, maybe this should instead be implemented as a function like
pg_backend_get_subxact_status(pid).

People who want to could use it like:
SELECT * FROM pg_stat_activity psa, pg_backend_get_subxact_status(pid) sub;

--
Justin