fix(0.3/2014-09-28--collection_slug.xml): don't prefix a column with table alias in SET clause on PostgreSQL.

The failure was:
liquibase.exception.DatabaseException: ERROR: column "c" of relation "collections" does not exist
Position: 29 [Failed SQL: UPDATE collections c SET c.slug = ( SELECT LOWER(REPLACE(u.login, ' ', '-')) FROM users u WHERE u.id = c.user_id) ]

See also: https://stackoverflow.com/questions/11369757/postgres-wont-accept-table-alias-before-column-name

Addressed to #1034

Author: php-coder

src/main/resources/liquibase/version/0.3/2014-09-28--collection_slug.xml

@@ -18,7 +18,7 @@
 		<comment>Sets value of slug field to transformed collection's owner's name</comment>
 
 		<!-- Unfortunately, H2 doesn't support UPDATE with JOIN -->
-		<sql>
+		<sql dbms="mysql,h2">
 			UPDATE collections c
 			SET c.slug = (
 				SELECT LOWER(REPLACE(u.login, ' ', '-'))
@@ -27,6 +27,16 @@
 			);
 		</sql>
 
+		<!-- In PostgreSQL it is illegal to prefix columns with table alias in the SET clause -->
+		<sql dbms="postgresql">
+			UPDATE collections c
+			SET slug = (
+				SELECT LOWER(REPLACE(u.login, ' ', '-'))
+				FROM users u
+				WHERE u.id = c.user_id
+			);
+		</sql>
+		
 	</changeSet>
 
 	<changeSet id="make-slug-field-not-nullable" author="php-coder" context="scheme">