Thanks! That did the trick. For posterity, I was able to do the final conversion using: alter table mytable alter column mycolumn type float4[] using string_to_array(trim(both '[]' from textin(nbf4a_out(mycolumn))),',')::float4[]; Mike Alvaro Herrera wrote: > Mike Charnoky wrote: >> OK, forgive my ignorance here, but the maintainer of our custom data >> type code is no longer with us and this is new territory for me. We do >> have a function which takes our custom data type and returns a cstring. >> Is there a pg function which converts a cstring to text type? This >> seems to be the missing link to eventually get the data to float4[]. > > Sure, textin() does that. > ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match