Specifying attribute slot for storing/reading statistics

In MobilityDB temporal types are types derived from PostgreSQL/PostGIS types to which a time dimension is added. MobilityDB provides the following temporal types: tbool (temporal boolean), tint (temporal int), tfloat (temporal float), text (temporal text), tgeompoint (temporal geometric points) and tgeogpoint (temporal geographic points). For example, we can define a tfloat and a tgeompoint as follows

SELECT tfloat '[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03]';
SELECT tgeompoint '[Point(0 0)@2000-01-01 08:00, Point(1 0)@2000-01-02 08:05, Point(1 1)@2000-01-03 08:10]';

We are developing the analyze/selectivity functions for those types. Our approach is to use the standard PostgreSQL/PostGIS functions for the value and the time dimensions where the slots starting from 0 will be used for the value dimension, and the slots starting from 2 will be used for the time dimension. For example, for tfloat we use range_typanalyze and related functions for

* collecting in slots 0 and 1, STATISTIC_KIND_BOUNDS_HISTOGRAM and STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM for the float ranges of the value dimension

*  collecting in slots 2 and 3, STATISTIC_KIND_BOUNDS_HISTOGRAM and STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM for the periods (similar to tstzranges) of the time dimension

However, we end up copying several PostgreSQL functions to which we only add an additional parameter stating the slot number from which the specific statistic kind should be found (either 0 or 2)