From 38d9f0f110a025d693bf5d804d9aec5a4b5868c1 Mon Sep 17 00:00:00 2001
From: Andrea Canciani <ranma42@gmail.com>
Date: Sun, 16 Jun 2024 11:32:09 +0200
Subject: [PATCH] Simplify `COALESCE`

Drop all of the arguments after the first non-nullable sub-expressions.
Simplify unary `COALESCE` to its argument.
---
 .../Query/SqlNullabilityProcessor.cs            | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/EFCore.Relational/Query/SqlNullabilityProcessor.cs b/src/EFCore.Relational/Query/SqlNullabilityProcessor.cs
index 4b2b44773c1..11cef72197c 100644
--- a/src/EFCore.Relational/Query/SqlNullabilityProcessor.cs
+++ b/src/EFCore.Relational/Query/SqlNullabilityProcessor.cs
@@ -1422,12 +1422,25 @@ protected virtual SqlExpression VisitSqlFunction(
             foreach (var argument in sqlFunctionExpression.Arguments)
             {
                 coalesceArguments.Add(Visit(argument, out var argumentNullable));
-                coalesceNullable = coalesceNullable && argumentNullable;
+                if (!argumentNullable)
+                {
+                    coalesceNullable = false;
+                    break;
+                }
             }
 
             nullable = coalesceNullable;
 
-            return sqlFunctionExpression.Update(sqlFunctionExpression.Instance, coalesceArguments);
+            return coalesceArguments switch
+            {
+                [var singleArgument] => singleArgument,
+
+                _ => sqlFunctionExpression.Update(
+                    sqlFunctionExpression.Instance,
+                    coalesceArguments,
+                    argumentsPropagateNullability: coalesceArguments.Select(_ => false).ToArray()
+                ),
+            };
         }
 
         var useNullabilityPropagation = sqlFunctionExpression is { InstancePropagatesNullability: true };