Allow SELECT statements to START AT 0

Closes #1516

lib/src/sql/number.rs

@@ -235,6 +235,30 @@ impl Number {
 		}
 	}
 
+	pub fn is_negative(&self) -> bool {
+		match self {
+			Number::Int(v) => v < &0,
+			Number::Float(v) => v < &0.0,
+			Number::Decimal(v) => v < &BigDecimal::from(0),
+		}
+	}
+
+	pub fn is_zero_or_positive(&self) -> bool {
+		match self {
+			Number::Int(v) => v >= &0,
+			Number::Float(v) => v >= &0.0,
+			Number::Decimal(v) => v >= &BigDecimal::from(0),
+		}
+	}
+
+	pub fn is_zero_or_negative(&self) -> bool {
+		match self {
+			Number::Int(v) => v <= &0,
+			Number::Float(v) => v <= &0.0,
+			Number::Decimal(v) => v <= &BigDecimal::from(0),
+		}
+	}
+
 	// -----------------------------------
 	// Simple conversion of number
 	// -----------------------------------

lib/src/sql/start.rs

@@ -23,7 +23,7 @@ impl Start {
 		doc: Option<&Value>,
 	) -> Result<usize, Error> {
 		match self.0.compute(ctx, opt, txn, doc).await {
-			Ok(v) if v.is_integer() && v.is_positive() => Ok(v.as_usize()),
+			Ok(v) if v.is_integer() && v.is_zero_or_positive() => Ok(v.as_usize()),
 			Ok(v) => Err(Error::InvalidStart {
 				value: v.as_string(),
 			}),

lib/src/sql/value/value.rs

@@ -698,6 +698,18 @@ impl Value {
 		matches!(self, Value::Number(v) if v.is_positive())
 	}
 
+	pub fn is_negative(&self) -> bool {
+		matches!(self, Value::Number(v) if v.is_negative())
+	}
+
+	pub fn is_zero_or_positive(&self) -> bool {
+		matches!(self, Value::Number(v) if v.is_zero_or_positive())
+	}
+
+	pub fn is_zero_or_negative(&self) -> bool {
+		matches!(self, Value::Number(v) if v.is_zero_or_negative())
+	}
+
 	pub fn is_datetime(&self) -> bool {
 		matches!(self, Value::Datetime(_))
 	}