pg_statistic_ext
The catalog pg_statistic_ext
holds extended planner statistics.
Each row in this catalog corresponds to a statistics object
created with CREATE STATISTICS.
Table 52.51. pg_statistic_ext
Columns
Name  Type  References  Description 

stxrelid  oid 
 Table containing the columns described by this object 
stxname  name  Name of the statistics object  
stxnamespace  oid 
 The OID of the namespace that contains this statistics object 
stxowner  oid 
 Owner of the statistics object 
stxkeys  int2vector 
 An array of attribute numbers, indicating which table columns are
covered by this statistics object;
for example a value of 1 3 would
mean that the first and the third table columns are covered

stxkind  char[]  An array containing codes for the enabled statistic kinds;
valid values are:
d for ndistinct statistics,
f for functional dependency statistics
 
stxndistinct  pg_ndistinct  Ndistinct counts, serialized as pg_ndistinct type
 
stxdependencies  pg_dependencies  Functional dependency statistics, serialized
as pg_dependencies type

The stxkind
field is filled at creation of the
statistics object, indicating which statistic type(s) are desired.
The fields after it are initially NULL and are filled only when the
corresponding statistic has been computed by ANALYZE
.