Add IsEmpty then FindSet patern vs only FindSet

content/docs/BestPractices/if-isempty-then-findset/index.md

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+---
+title: "if not IsEmpty then FindSet"
+tags: ["AL","Performance"]
+categories: ["Best Practice"]
+---
+
+_Created by SosicStefan, Described by SosicStefan_
+
+## Introduction
+
+When retrieving records in Business Central, a common pattern is using `IsEmpty` before calling `FindSet` to check whether data exists. However, this approach is redundant and can lead to unnecessary database queries. Business Central’s runtime already optimizes `FindSet` to avoid unnecessary retrieval operations.
+
+## Why Not Use 'If Not IsEmpty Then FindSet'?
+
+The following pattern:
+
+```al
+if not Customer.IsEmpty() then
+    Customer.FindSet();
+```
+
+This introduces inefficiencies due to:
+- Redundant checks: Business Central internally wraps FindSet in an IF EXISTS query when repeated on platform level itself.
+- Extra queries: Calling IsEmpty separately can lead to duplicate execution of SELECT TOP 1 NULL, slowing down performance.
+
+## How Business Central Optimizes FindSet
+
+Consider the following loop:
+
+```al
+internal procedure IsEmptyAndFindSet()
+var
+    Customer: Record Customer;
+    i: Integer;
+begin
+    for i := 1 to 10 do begin
+        Customer.SetRange("Country/Region Code", 'RS');
+        if not Customer.IsEmpty() then
+            Customer.FindSet();
+    end;
+end;
+```
+
+With this code being executed, Business Central will run two queries on SQL:
+- One for checking `IsEmpty`
+- Second for getting dataset with `FindSet`
+
+![image](isempty-then-findset-query.png)
+
+
+## Best Practice: Use FindSet Directly
+
+Instead of checking `IsEmpty` first, simply use only `FindSet`:
+```al
+internal procedure FindSetWithoutIsEmpty()
+var
+    Customer: Record Customer;
+    i: Integer;
+begin
+    for i := 1 to 10 do begin
+        Customer.SetRange("Country/Region Code", 'RS');
+        if Customer.FindSet() then;
+    end;
+end;
+```
+
+Initially, Business Central runs a normal `SELECT` query to retrieve the data.
+
+![image](findset-only-firstrun-query.png)
+
+However, after running this query for three times, on fourth time the system switches to an optimized query:
+
+![image](findset-only-after-optimization-query.png)
+
+After optimized query, the platform already applies the `IF EXISTS` logic dynamically. Means that explicitly calling `IsEmpty` before `FindSet` is unnecessary.
+
+Full query execution looks like this:
+
+![image](findset-only-full-flow-query.png)
+
+## Summary
+Avoid using if not `IsEmpty` then `FindSet`, as Business Central optimizes `FindSet` at the runtime level. This approach eliminates redundant queries, improves performance, and ensures cleaner code.