From ead608817b4d4c47993cc7241e45285fe6723587 Mon Sep 17 00:00:00 2001
From: Sergey Dudoladov <sergey.dudoladov@gmail.com>
Date: Thu, 19 Oct 2023 17:42:42 +0200
Subject: [PATCH 1/3] add function to monitor sequences

---
 postgres-appliance/scripts/metric_helpers.sql | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/postgres-appliance/scripts/metric_helpers.sql b/postgres-appliance/scripts/metric_helpers.sql
index 89abd09c4..9df9512bd 100644
--- a/postgres-appliance/scripts/metric_helpers.sql
+++ b/postgres-appliance/scripts/metric_helpers.sql
@@ -193,6 +193,41 @@ $$ LANGUAGE sql IMMUTABLE SECURITY DEFINER STRICT;
 
 CREATE OR REPLACE VIEW pg_stat_statements AS SELECT * FROM pg_stat_statements(true);
 
+CREATE OR REPLACE FUNCTION get_nearly_exhausted_sequences(
+    IN  threshold float,
+    OUT schemaname name,
+    OUT sequencename name,
+    OUT max_value int8,
+    OUT increment_by int8,
+    OUT last_value int8,
+    OUT percent_used numeric
+ ) RETURNS SETOF record AS
+$_$
+WITH t AS (
+    SELECT
+      schemaname,
+      sequencename,
+      max_value,
+      increment_by,
+      last_value,
+      abs(last_value - start_value / increment_by)::numeric as used_sequence,
+      (max_value - min_value) / abs(increment_by)::numeric as sequence_capacity
+    FROM pg_sequences 
+    WHERE last_value IS NOT NULL
+) SELECT 
+    schemaname,
+    sequencename,
+    max_value,
+    increment_by,
+    last_value,
+    round(used_sequence / sequence_capacity * 100, 2) as percent_used
+  FROM t 
+  WHERE used_sequence / sequence_capacity > threshold
+$_$
+LANGUAGE sql SECURITY DEFINER STRICT SET search_path to 'pg_catalog';
+
+CREATE OR REPLACE VIEW nearly_exhausted_sequences AS SELECT * FROM get_nearly_exhausted_sequences(0.8);
+
 REVOKE ALL ON ALL TABLES IN SCHEMA metric_helpers FROM public;
 GRANT SELECT ON ALL TABLES IN SCHEMA metric_helpers TO admin, robot_zmon;
 

From 6c43272c2f29e159e9a28e45e5213829ba3557c2 Mon Sep 17 00:00:00 2001
From: Sergey Dudoladov <sergey.dudoladov@gmail.com>
Date: Fri, 3 Nov 2023 10:23:02 +0100
Subject: [PATCH 2/3] add a new query that covers many more cases

---
 postgres-appliance/scripts/metric_helpers.sql | 34 +++++++------------
 1 file changed, 12 insertions(+), 22 deletions(-)

diff --git a/postgres-appliance/scripts/metric_helpers.sql b/postgres-appliance/scripts/metric_helpers.sql
index 9df9512bd..a15e458fe 100644
--- a/postgres-appliance/scripts/metric_helpers.sql
+++ b/postgres-appliance/scripts/metric_helpers.sql
@@ -197,32 +197,22 @@ CREATE OR REPLACE FUNCTION get_nearly_exhausted_sequences(
     IN  threshold float,
     OUT schemaname name,
     OUT sequencename name,
-    OUT max_value int8,
-    OUT increment_by int8,
-    OUT last_value int8,
-    OUT percent_used numeric
+    OUT seq_percent_used numeric
  ) RETURNS SETOF record AS
 $_$
-WITH t AS (
-    SELECT
-      schemaname,
-      sequencename,
-      max_value,
-      increment_by,
-      last_value,
-      abs(last_value - start_value / increment_by)::numeric as used_sequence,
-      (max_value - min_value) / abs(increment_by)::numeric as sequence_capacity
-    FROM pg_sequences 
-    WHERE last_value IS NOT NULL
-) SELECT 
+SELECT *
+FROM (
+  SELECT
     schemaname,
     sequencename,
-    max_value,
-    increment_by,
-    last_value,
-    round(used_sequence / sequence_capacity * 100, 2) as percent_used
-  FROM t 
-  WHERE used_sequence / sequence_capacity > threshold
+    round(
+      (abs(last_value::numeric - start_value) + 1) / 
+      (CASE WHEN increment_by > 0 THEN (max_value::numeric - start_value) ELSE (start_value::numeric - min_value) END + 1) * 100,
+    2) as seq_percent_used
+  FROM pg_sequences
+  WHERE NOT CYCLE AND last_value IS NOT NULL
+  ) AS s
+WHERE seq_percent_used >= threshold;
 $_$
 LANGUAGE sql SECURITY DEFINER STRICT SET search_path to 'pg_catalog';
 

From c82430a32ca6da87783df265192a50c6a481c7c4 Mon Sep 17 00:00:00 2001
From: Sergey Dudoladov <sergey.dudoladov@gmail.com>
Date: Tue, 9 Jan 2024 09:20:59 +0100
Subject: [PATCH 3/3] update query based on review

---
 postgres-appliance/scripts/metric_helpers.sql | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/postgres-appliance/scripts/metric_helpers.sql b/postgres-appliance/scripts/metric_helpers.sql
index a15e458fe..5aa939993 100644
--- a/postgres-appliance/scripts/metric_helpers.sql
+++ b/postgres-appliance/scripts/metric_helpers.sql
@@ -202,16 +202,21 @@ CREATE OR REPLACE FUNCTION get_nearly_exhausted_sequences(
 $_$
 SELECT *
 FROM (
-  SELECT
+  SELECT 
     schemaname,
     sequencename,
-    round(
-      (abs(last_value::numeric - start_value) + 1) / 
-      (CASE WHEN increment_by > 0 THEN (max_value::numeric - start_value) ELSE (start_value::numeric - min_value) END + 1) * 100,
-    2) as seq_percent_used
+    round(abs(
+      ceil((abs(last_value::numeric - start_value) + 1) / increment_by) / 
+        floor((CASE WHEN increment_by > 0
+                    THEN (max_value::numeric - start_value)
+                    ELSE (start_value::numeric - min_value)
+                    END + 1) / increment_by
+              ) * 100 
+      ), 
+    2) AS seq_percent_used
   FROM pg_sequences
   WHERE NOT CYCLE AND last_value IS NOT NULL
-  ) AS s
+) AS s
 WHERE seq_percent_used >= threshold;
 $_$
 LANGUAGE sql SECURITY DEFINER STRICT SET search_path to 'pg_catalog';