Rename my existing store procedure in xml

I want to rename my existing store procedure in xml using postgresql first we check if procedure exist then i want to rename my procedure

i am trying to this way




<!-- Rename the procedure if it exists -->
<changeSet id="2" author="${schema_name}" dependsOn="1">
<sql>
<![CDATA[
		ALTER PROCEDURE ${procedure_name} RENAME TO ${backup_name};
	]]>
</sql>