Made LOAD DATA handle NULL values and defaults correctly

enginetest/queries/load_queries.go

@@ -22,6 +22,20 @@ import (
 )
 
 var LoadDataScripts = []ScriptTest{
+	{
+		Name: "LOAD DATA applies column defaults when \\N provided",
+		SetUpScript: []string{
+			"create table t (pk int primary key, c1 int default 1, c2 int)",
+			// Explicitly use Windows-style line endings to be robust on Windows CI
+			"LOAD DATA INFILE './testdata/load_defaults_null.csv' INTO TABLE t FIELDS TERMINATED BY ',' LINES TERMINATED BY '\r\n'",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Query:    "select * from t",
+				Expected: []sql.Row{{1, 1, 1}},
+			},
+		},
+	},
 	{
 		Name: "Basic load data with enclosed values.",
 		SetUpScript: []string{

enginetest/testdata/load_defaults_null.csv

@@ -0,0 +1 @@
+1,\N,1

sql/rowexec/ddl_iters.go

@@ -207,7 +207,19 @@ func (l *loadDataIter) parseFields(ctx *sql.Context, line string) ([]sql.Express
 				}
 			}
 		case "NULL":
-			exprs[exprIdx] = expression.NewLiteral(nil, types.Null)
+			// For MySQL LOAD DATA semantics, \N (mapped to NULL here) should use the column default
+			// if one exists; otherwise insert NULL.
+			destIdx := l.fieldToColMap[fieldIdx]
+			if destIdx >= 0 {
+				destCol := l.destSch[destIdx]
+				if destCol.Default != nil {
+					exprs[exprIdx] = destCol.Default
+				} else {
+					exprs[exprIdx] = expression.NewLiteral(nil, types.Null)
+				}
+			} else {
+				exprs[exprIdx] = expression.NewLiteral(nil, types.Null)
+			}
 		default:
 			exprs[exprIdx] = expression.NewLiteral(field, types.LongText)
 		}