--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/PostgreSQL/Plugins/FastCountResources.sql	Tue Jan 08 14:37:41 2019 +0100
@@ -0,0 +1,33 @@
+-- https://wiki.postgresql.org/wiki/Count_estimate
+
+INSERT INTO GlobalIntegers
+SELECT 2, CAST(COALESCE(COUNT(*), 0) AS BIGINT) FROM Resources WHERE resourceType = 0;  -- Count patients
+
+INSERT INTO GlobalIntegers
+SELECT 3, CAST(COALESCE(COUNT(*), 0) AS BIGINT) FROM Resources WHERE resourceType = 1;  -- Count studies
+
+INSERT INTO GlobalIntegers
+SELECT 4, CAST(COALESCE(COUNT(*), 0) AS BIGINT) FROM Resources WHERE resourceType = 2;  -- Count series
+
+INSERT INTO GlobalIntegers
+SELECT 5, CAST(COALESCE(COUNT(*), 0) AS BIGINT) FROM Resources WHERE resourceType = 3;  -- Count instances
+
+
+CREATE OR REPLACE FUNCTION CountResourcesTrackerFunc()
+RETURNS TRIGGER AS $$
+BEGIN
+  IF TG_OP = 'INSERT' THEN
+    UPDATE GlobalIntegers SET value = value + 1 WHERE key = new.resourceType + 2;
+    RETURN new;
+  ELSIF TG_OP = 'DELETE' THEN
+    UPDATE GlobalIntegers SET value = value - 1 WHERE key = old.resourceType + 2;
+    RETURN old;
+  END IF;
+END;
+$$ LANGUAGE plpgsql;
+
+
+CREATE TRIGGER CountResourcesTracker
+AFTER INSERT OR DELETE ON Resources
+FOR EACH ROW
+EXECUTE PROCEDURE CountResourcesTrackerFunc();