What is the best for index field, and space token on hard disk/RAM? Biginteger or Varchar(15) ?
I can have for example such index number:
from 10000001 to 45281229703 and higher...
BIGINT is always 8 bytes,
VARCHAR(15) is 1..16 bytes depending on value length, so
BIGINT needs less memory on large numnbers, but more memory on small numbers (shorter than 7 digits). Also, BIGINT is faster.