Avoid nested loop in query planner execution (dbt-labs#612)

* Adjust not equals application order

  - Move relation name not equals from outer SELECT `where` clause
    to dependency CTE
      - Seems to more reliably push query planner to avoid a nested
        loop
      - Should preserve original intent, i.e. to exclude
        self-references from final result
      - Execution plan suggests this reduces the row estimate for
        the outer SELECT
      - Real-world testing on internal company cluster under
        conditions where nested loop is used for original, shows
	that the new approach continues to perform and behave as
	expected (no nested loop)

* Add changie entry

.changes/unreleased/Fixes-20230923-091155.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: avoid nested loop in query planner execution of redshift__get_relations
+time: 2023-09-23T09:11:55.2152725-04:00
+custom:
+  Author: slin30
+  Issue: "609"

dbt/include/redshift/macros/relations.sql

@@ -24,6 +24,7 @@ with
         from pg_depend
         left join pg_rewrite
           on pg_depend.objid = pg_rewrite.oid
+        where coalesce(pg_rewrite.ev_class, pg_depend.objid) != pg_depend.refobjid
     )
 
 select distinct
@@ -36,7 +37,6 @@ join relation ref
     on dependency.ref_relation_id = ref.relation_id
 join relation dep
     on dependency.dep_relation_id = dep.relation_id
-where ref.relation_name != dep.relation_name
 
 {%- endcall -%}