Evaluate an expression in the context of a single row.
(expr: &Expr, row: &[VValue], table: &VTable)
| 59 | |
| 60 | /// Evaluate an expression in the context of a single row. |
| 61 | pub fn eval(expr: &Expr, row: &[VValue], table: &VTable) -> Result<VValue, EvalError> { |
| 62 | match expr { |
| 63 | Expr::Literal(v) => Ok(v.clone()), |
| 64 | Expr::Star => Ok(VValue::Null), |
| 65 | Expr::Column(name) => { |
| 66 | let idx = table |
| 67 | .column_index(name) |
| 68 | .ok_or_else(|| EvalError::UnknownColumn(name.clone()))?; |
| 69 | Ok(row[idx].clone()) |
| 70 | } |
| 71 | Expr::UnaryNot(e) => { |
| 72 | let v = eval(e, row, table)?; |
| 73 | match v { |
| 74 | VValue::Null => Ok(VValue::Null), |
| 75 | VValue::Bool(b) => Ok(VValue::Bool(!b)), |
| 76 | _ => Err(EvalError::TypeMismatch("NOT requires boolean".into())), |
| 77 | } |
| 78 | } |
| 79 | Expr::UnaryNeg(e) => { |
| 80 | let v = eval(e, row, table)?; |
| 81 | match v { |
| 82 | VValue::Null => Ok(VValue::Null), |
| 83 | VValue::Int4(i) => Ok(VValue::Int4(-i)), |
| 84 | VValue::Int8(i) => Ok(VValue::Int8(-i)), |
| 85 | _ => Err(EvalError::TypeMismatch("unary - on non-integer".into())), |
| 86 | } |
| 87 | } |
| 88 | Expr::IsNull(e, negated) => { |
| 89 | let v = eval(e, row, table)?; |
| 90 | let is_null = v.is_null(); |
| 91 | Ok(VValue::Bool(if *negated { !is_null } else { is_null })) |
| 92 | } |
| 93 | Expr::BinaryOp(l, op, r) => { |
| 94 | let lv = eval(l, row, table)?; |
| 95 | let rv = eval(r, row, table)?; |
| 96 | apply_binary(op, &lv, &rv) |
| 97 | } |
| 98 | Expr::InList(e, items, negated) => { |
| 99 | let v = eval(e, row, table)?; |
| 100 | if v.is_null() { |
| 101 | return Ok(VValue::Null); |
| 102 | } |
| 103 | let mut found = false; |
| 104 | let mut any_null = false; |
| 105 | for item in items { |
| 106 | let iv = eval(item, row, table)?; |
| 107 | if iv.is_null() { |
| 108 | any_null = true; |
| 109 | continue; |
| 110 | } |
| 111 | if let Some(std::cmp::Ordering::Equal) = v.sql_cmp(&iv) { |
| 112 | found = true; |
| 113 | break; |
| 114 | } |
| 115 | } |
| 116 | let result = if found { |
| 117 | true |
| 118 | } else if any_null { |
no test coverage detected