what DBC table(s) does the partition infomation come from when I do a show table? ex:
PRIMARY INDEX NUPI_mytable_15 ( col1,col2,START_DT)
PARTITION BY ( RANGE_N(START_DT BETWEEN DATE - 15 AND DATE + 140 EACH INTERVAL '1' DAY ),
RANGE_N(START_H BETWEEN 0 AND 23 EACH 1 ) );
SHOW TABLE doesn't read the system tables (some info like DATABLOCKSIZE is not stored in there), but the partitioning information is found in dbc.IndexConstraintsV or dbc.PartitioningConstraintsV (in TD14).
It gets the information from internal data structures and in particular , for partitioning, it gets it from the table headers.