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Contents
module MigrationConstraintHelpers
# Creates a foreign key from +table+.+field+ against referenced_table.referenced_field
#
# table: The tablename
# field: A field of the table
# referenced_table: The table which contains the field referenced
# referenced_field: The field (which should be part of the primary key) of the referenced table
# cascade: delete & update on cascade?
def foreign_key(table, field, referenced_table, referenced_field = :id, cascade = true)
execute "ALTER TABLE #{table} ADD CONSTRAINT #{constraint_name(table, field)}
FOREIGN KEY #{constraint_name(table, field)} (#{field_list(field)})
REFERENCES #{referenced_table}(#{field_list(referenced_field)})
#{(cascade ? 'ON DELETE CASCADE ON UPDATE CASCADE' : '')}"
end
# Drops a foreign key from +table+.+field+ that has been created before with
# foreign_key method
#
# table: The table name
# field: A field (or array of fields) of the table
def drop_foreign_key(table, field)
execute "ALTER TABLE #{table} DROP FOREIGN KEY #{constraint_name(table, field)}"
end
# Creates a primary key for +table+, which right now HAS NOT primary key defined
#
# table: The table name
# field: A field (or array of fields) of the table that will be part of the primary key
def primary_key(table, field)
execute "ALTER TABLE #{table} ADD PRIMARY KEY(#{field_list(field)})"
end
private
# Creates a constraint name for table and field given as parameters
#
# table: The table name
# field: A field of the table
def constraint_name(table, field)
"fk_#{table}_#{field_list_name(field)}"
end
def field_list(fields)
fields.is_a?(Array) ? fields.join(',') : fields
end
def field_list_name(fields)
fields.is_a?(Array) ? fields.join('_') : fields
end
end
Version data entries
106 entries across 103 versions & 9 rubygems