Adjust tuplestore stats API
1eff8279d added an API to tuplestore.c to allow callers to obtain
storage telemetry data. That API wasn't quite good enough for callers
that perform tuplestore_clear() as the telemetry functions only
accounted for the current state of the tuplestore, not the maximums
before tuplestore_clear() was called.
There's a pending patch that would like to add tuplestore telemetry
output to EXPLAIN ANALYZE for WindowAgg. That node type uses
tuplestore_clear() before moving to the next window partition and we
want to show the maximum space used, not the space used for the final
partition.
Reviewed-by: Tatsuo Ishii, Ashutosh Bapat
Discussion: https://postgres/m/CAApHDvoY8cibGcicLV0fNh=9JVx9PANcWvhkdjBnDCc9Quqytg@mail.gmail.com