ARGCONST

The ARGCONST global variable indicates which arguments are constants instead of being variables that come from a calculation or a table.

For example, in the following SQL statement:

The first argument is from a table, so ARGCONST[1] would be false.
The second and third arguments for the substr function are constants, so both ARGCONST[2] and ARGCONST[3] would be true.

select substr(str, 1, 4) from strings