Fix RecordsAffected incorrectly accumulating counts from DDL statements (#37397)

Author: Copilot

src/Microsoft.Data.Sqlite.Core/SqliteDataReader.cs

@@ -154,6 +154,9 @@ public override bool NextResult()
             {
                 stmt = _stmtEnumerator.Current;
 
+                var connectionHandle = _command.Connection!.Handle;
+                var totalChangesBefore = sqlite3_total_changes(connectionHandle);
+
                 var timer = SharedStopwatch.StartNew();
 
                 while (IsBusy(rc = sqlite3_step(stmt)))
@@ -172,7 +175,7 @@ public override bool NextResult()
 
                 _totalElapsedTime += timer.Elapsed;
 
-                SqliteException.ThrowExceptionForRC(rc, _command.Connection!.Handle);
+                SqliteException.ThrowExceptionForRC(rc, connectionHandle);
 
                 // It's a SELECT statement
                 if (sqlite3_column_count(stmt) != 0)
@@ -185,13 +188,26 @@ public override bool NextResult()
                 while (rc != SQLITE_DONE)
                 {
                     rc = sqlite3_step(stmt);
-                    SqliteException.ThrowExceptionForRC(rc, _command.Connection.Handle);
+                    SqliteException.ThrowExceptionForRC(rc, connectionHandle);
                 }
 
                 sqlite3_reset(stmt);
 
-                var changes = sqlite3_changes(_command.Connection.Handle);
-                AddChanges(changes);
+                // sqlite3_changes() returns the row count from the most recent INSERT, UPDATE, or DELETE
+                // and incorrectly persists across DDL statements. Use sqlite3_total_changes() before and after
+                // to calculate the actual delta for this statement, ensuring DDL statements don't add stale counts.
+                var totalChangesAfter = sqlite3_total_changes(connectionHandle);
+                var changes = totalChangesAfter - totalChangesBefore;
+                // sqlite3_total_changes, unfortunately, counts also changes from triggers, etc. which is not what we want.
+                // So we use it only to detect changes and if so, use sqlite3_changes.
+                if (changes > 0)
+                {
+                    AddChanges(sqlite3_changes(connectionHandle));
+                }
+                else
+                {
+                    AddChanges(0);
+                }
             }
             catch
             {

test/Microsoft.Data.Sqlite.Tests/SqliteConnectionTest.cs

@@ -812,7 +812,7 @@ public void CreateFunction_deterministic_param_works()
         connection.ExecuteNonQuery("CREATE TABLE Data (Value); INSERT INTO Data VALUES (0);");
         connection.CreateFunction("test", (double x) => x, true);
 
-        Assert.Equal(1, connection.ExecuteNonQuery("CREATE INDEX InvalidIndex ON Data (Value) WHERE test(Value) = 0;"));
+        Assert.Equal(0, connection.ExecuteNonQuery("CREATE INDEX InvalidIndex ON Data (Value) WHERE test(Value) = 0;"));
     }
 
     [Fact]

test/Microsoft.Data.Sqlite.Tests/SqliteDataReaderTest.cs

@@ -1970,6 +1970,45 @@ public void RecordsAffected_works_with_returning_multiple()
         }
     }
 
+    [Fact]
+    public void RecordsAffected_not_affected_by_DDL_statements()
+    {
+        using (var connection = new SqliteConnection("Data Source=:memory:"))
+        {
+            connection.Open();
+
+            using (var reader = connection.ExecuteReader(
+                @"CREATE TABLE foo(bar TEXT NOT NULL);
+                  CREATE TABLE xyz(aaa TEXT NOT NULL);
+                  INSERT INTO foo(bar) VALUES('baz');
+                  INSERT INTO foo(bar) VALUES('baz2');
+                  DROP TABLE xyz;"))
+            {
+                Assert.Equal(2, reader.RecordsAffected);
+            }
+        }
+    }
+
+    [Fact]
+    public void RecordsAffected_not_affected_by_DDL_statements_with_drop_and_create()
+    {
+        using (var connection = new SqliteConnection("Data Source=:memory:"))
+        {
+            connection.Open();
+
+            using (var reader = connection.ExecuteReader(
+                @"CREATE TABLE foo(bar TEXT NOT NULL);
+                  CREATE TABLE xyz(aaa TEXT NOT NULL);
+                  INSERT INTO foo(bar) VALUES('baz');
+                  INSERT INTO foo(bar) VALUES('baz2');
+                  DROP TABLE xyz;
+                  CREATE TABLE xyz(aaa TEXT NOT NULL);"))
+            {
+                Assert.Equal(2, reader.RecordsAffected);
+            }
+        }
+    }
+
     [Fact]
     public void GetSchemaTable_works()
     {