Omit .* regex filter (#19470)

* Omit .* regex filter

* Changelog

* Changelog

* Stub filter

Author: sethsamuel

postgres/changelog.d/19470.fixed

@@ -0,0 +1 @@
+Omit .* regex filter to avoid unnecessary work in query

postgres/datadog_checks/postgres/relationsmanager.py

@@ -408,8 +408,11 @@ def filter_relation_query(self, query, schema_field):
             relation_filter = []
             if r.get(RELATION_NAME):
                 relation_filter.append("( relname = '{}'".format(r[RELATION_NAME]))
-            elif r.get(RELATION_REGEX):
+            elif r.get(RELATION_REGEX) and r.get(RELATION_REGEX) != ".*":
                 relation_filter.append("( relname ~ '{}'".format(r[RELATION_REGEX]))
+            else:
+                # Stub filter to allow for appending
+                relation_filter.append("( 1=1")
 
             if ALL_SCHEMAS not in r[SCHEMAS]:
                 schema_filter = ','.join("'{}'".format(s) for s in r[SCHEMAS])