change_column fails to fully respect provided fk and index names

[wrkrb33]

I am iteratively developing a script to add foreign key constraints throughout a postgres database. In some cases the usual concatenation of table and column names to construct constraint and index names produces names that exceed the permitted length, so in those cases I am providing my own names. E.g.,

change_column("staffing_plan_category_item_pairings", "staffing_plan_category_id", :integer, {:foreign_key=>{:name=>"fk_spcip_sp_category_id"}, :index=>{:name=>"fk__spcip_sp_category_id"}})

This works fine the first time through. However, if I re-run the migration, schema_plus wants to first make an attempt to drop the constraint if, but it does that without reference to the name I've provided, resulting in an error:

NOTICE:  identifier "fk_staffing_plan_category_item_pairings_staffing_plan_category_id" will be truncated to "fk_staffing_plan_category_item_pairings_staffing_plan_category_"
rake aborted!
PG::UndefinedObject: ERROR:  constraint "fk_staffing_plan_category_item_pairings_staffing_plan_category_" of relation "staffing_plan_category_item_pairings" does not exist
: ALTER TABLE "staffing_plan_category_item_pairings" DROP CONSTRAINT fk_staffing_plan_category_item_pairings_staffing_plan_category_id

I am able to work around the problem by manually deleting the constraints and indexes in question.