Table: gnri_class
Columns: class
gnri_no
name
bp_serial_no
rebuilt
1958
withdrawn

Question: What is the smallest withdrawn value with a GNRI greater than 172, name of Croagh Patrick and was rebuilt before 1939?
SQL: SELECT MIN("withdrawn") FROM gnri_class WHERE "gnri_no" > 172 AND "name" = 'croagh patrick' AND "rebuilt" < 1939