amend test placement and decimal validation

Author: elianddb

enginetest/queries/script_queries.go

@@ -10529,7 +10529,10 @@ where
 					{types.NewOkResult(3)},
 				},
 			},
-
+			{
+				Query:       "insert into child_dec_4_2 values (99.99);",
+				ExpectedErr: sql.ErrForeignKeyChildViolation,
+			},
 			{
 				Query: "create table child_dec_4_1 (d decimal(4,1), foreign key (d) references parent (d));",
 				Expected: []sql.Row{
@@ -10540,7 +10543,10 @@ where
 				Query:       "insert into child_dec_4_1 values (78.9);",
 				ExpectedErr: sql.ErrForeignKeyChildViolation,
 			},
-
+			{
+				Query:       "insert into child_dec_4_1 values (99.9);",
+				ExpectedErr: sql.ErrForeignKeyChildViolation,
+			},
 			{
 				Query: "create table child_dec_3_2 (d decimal(3,2), foreign key (d) references parent (d));",
 				Expected: []sql.Row{
@@ -10563,14 +10569,6 @@ where
 				Query:       "insert into child_dec_65_30 values (1.23);",
 				ExpectedErr: sql.ErrForeignKeyChildViolation,
 			},
-			{
-				Query:       "insert into child_dec_4_2 values (99.99);",
-				ExpectedErr: sql.ErrForeignKeyChildViolation,
-			},
-			{
-				Query:       "insert into child_dec_4_1 values (99.9);",
-				ExpectedErr: sql.ErrForeignKeyChildViolation,
-			},
 			{
 				Query: "create table child_multi_4_2_3_1 (d1 decimal(4,2), d2 decimal(3,1), foreign key (d1, d2) references parent_multi (d1, d2));",
 				Expected: []sql.Row{

sql/plan/foreign_key_editor.go

@@ -548,28 +548,31 @@ func (reference *ForeignKeyReferenceHandler) validateDecimalConstraints(row sql.
 	if reference.RowMapper.Index == nil {
 		return nil
 	}
-
 	indexColumnTypes := reference.RowMapper.Index.ColumnExpressionTypes()
-	for i := range reference.ForeignKey.Columns {
-		if i >= len(indexColumnTypes) {
-			continue
+	for parentIdx, parentCol := range indexColumnTypes {
+		if parentIdx >= len(reference.RowMapper.IndexPositions) {
+			break
 		}
-
-		childColIdx := reference.RowMapper.IndexPositions[i]
+		parentType := parentCol.Type
+		childColIdx := reference.RowMapper.IndexPositions[parentIdx]
 		childType := reference.RowMapper.SourceSch[childColIdx].Type
-		parentType := indexColumnTypes[i].Type
-
-		// For decimal types, check scale compatibility (following existing pattern for type-specific validation)
-		if childDecimal, ok := childType.(sql.DecimalType); ok {
-			if parentDecimal, ok := parentType.(sql.DecimalType); ok {
-				if childDecimal.Scale() != parentDecimal.Scale() {
-					return sql.ErrForeignKeyChildViolation.New(reference.ForeignKey.Name, reference.ForeignKey.Table,
-						reference.ForeignKey.ParentTable, reference.RowMapper.GetKeyString(row))
-				}
-			}
+		childDecimal, ok := childType.(sql.DecimalType)
+		if !ok {
+			continue
+		}
+		parentDecimal, ok := parentType.(sql.DecimalType)
+		if !ok {
+			continue
+		}
+		if childDecimal.Scale() != parentDecimal.Scale() {
+			return sql.ErrForeignKeyChildViolation.New(
+				reference.ForeignKey.Name,
+				reference.ForeignKey.Table,
+				reference.ForeignKey.ParentTable,
+				reference.RowMapper.GetKeyString(row),
+			)
 		}
 	}
-
 	return nil
 }