Eval implements the sql.Expression interface.
(ctx *sql.Context, row sql.Row)
| 67 | |
| 68 | // Eval implements the sql.Expression interface. |
| 69 | func (s Subscript) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) { |
| 70 | childVal, err := s.Child.Eval(ctx, row) |
| 71 | if err != nil { |
| 72 | return nil, err |
| 73 | } |
| 74 | if childVal == nil { |
| 75 | return nil, nil |
| 76 | } |
| 77 | |
| 78 | indexVal, err := s.Index.Eval(ctx, row) |
| 79 | if err != nil { |
| 80 | return nil, err |
| 81 | } |
| 82 | if indexVal == nil { |
| 83 | return nil, nil |
| 84 | } |
| 85 | |
| 86 | switch child := childVal.(type) { |
| 87 | case []interface{}: |
| 88 | index, ok := indexVal.(int32) |
| 89 | if !ok { |
| 90 | converted, _, err := types.Int32.Convert(ctx, indexVal) |
| 91 | if err != nil { |
| 92 | return nil, err |
| 93 | } |
| 94 | index = converted.(int32) |
| 95 | } |
| 96 | |
| 97 | // subscripts are 1-based |
| 98 | if index < 1 || int(index) > len(child) { |
| 99 | return nil, nil |
| 100 | } |
| 101 | return child[index-1], nil |
| 102 | default: |
| 103 | return nil, fmt.Errorf("unsupported type %T for subscript", child) |
| 104 | } |
| 105 | } |
| 106 | |
| 107 | // Children implements the sql.Expression interface. |
| 108 | func (s Subscript) Children() []sql.Expression { |