Best way to calculate row size with pg_getline?

I'm trying to determine the best value to use with pg_getline for the
"size" value. The docs say:

"The second argument is the size of the variable: this should be greater
than the expected size of the row. "

I have a table with many columns including several "text" fields. I'm
not sure how to calculate a row size that would be good to use here.
Suggestions?

I'm hoping there might be an "auto" option, which would just calculate
the length of the row as it passes through, and raise the value if needed.

I'm used to the land of Perl, where it generally doesn't care how big my
content is before I stuff into a variable.

   Mark