From 07debd98a70deb626aa82a4ca635baa01e646e69 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Wed, 14 Jan 2026 18:59:48 -0600
Subject: [PATCH] Optimize equipment assignment breakdown N+1 query

Replaced application-level logic with single SQL query using CASE statement
to determine assignment source directly in the database.

Before: Loaded all equipment, called get_effective_agent_token_with_source
for each (500 equipment = 500+ queries)

After: Single query with CASE statement to classify assignment source

Performance improvement: Reduces from O(n) queries to 1 query regardless
of equipment count.
---
 lib/towerops/agents/stats.ex | 49 ++++++++++++++++++++++++------------
 1 file changed, 33 insertions(+), 16 deletions(-)

diff --git a/lib/towerops/agents/stats.ex b/lib/towerops/agents/stats.ex
index 47bc86b3..7e012dc5 100644
--- a/lib/towerops/agents/stats.ex
+++ b/lib/towerops/agents/stats.ex
@@ -91,25 +91,42 @@ defmodule Towerops.Agents.Stats do
       }
   """
   def get_equipment_assignment_breakdown(organization_id) do
-    # Get all equipment for organization
-    equipment_query =
-      from(e in Equipment,
-        join: s in assoc(e, :site),
-        where: s.organization_id == ^organization_id and e.snmp_enabled == true,
-        preload: [:site, site: :organization]
+    # Use a single SQL query with CASE to determine assignment source
+    # This avoids loading all equipment into memory and calling get_effective_agent_token_with_source
+    results =
+      Repo.all(
+        from(e in Equipment,
+          join: s in assoc(e, :site),
+          join: o in assoc(s, :organization),
+          left_join: aa in AgentAssignment,
+          on: aa.equipment_id == e.id and aa.enabled == true,
+          where: s.organization_id == ^organization_id and e.snmp_enabled == true,
+          select: %{
+            source:
+              fragment(
+                """
+                CASE
+                  WHEN ? IS NOT NULL THEN 'equipment'
+                  WHEN ? IS NOT NULL THEN 'site'
+                  WHEN ? IS NOT NULL THEN 'organization'
+                  ELSE 'cloud'
+                END
+                """,
+                aa.agent_token_id,
+                s.agent_token_id,
+                o.default_agent_token_id
+              )
+          }
+        )
       )
 
-    equipment_list = Repo.all(equipment_query)
-
-    # Count by assignment type
-    Enum.reduce(equipment_list, %{direct: 0, site: 0, organization: 0, cloud: 0}, fn eq, acc ->
-      {_agent_id, source} = Towerops.Agents.get_effective_agent_token_with_source(eq)
-
+    # Count by assignment source
+    Enum.reduce(results, %{direct: 0, site: 0, organization: 0, cloud: 0}, fn %{source: source}, acc ->
       case source do
-        :equipment -> %{acc | direct: acc.direct + 1}
-        :site -> %{acc | site: acc.site + 1}
-        :organization -> %{acc | organization: acc.organization + 1}
-        :none -> %{acc | cloud: acc.cloud + 1}
+        "equipment" -> %{acc | direct: acc.direct + 1}
+        "site" -> %{acc | site: acc.site + 1}
+        "organization" -> %{acc | organization: acc.organization + 1}
+        "cloud" -> %{acc | cloud: acc.cloud + 1}
       end
     end)
   end