Merge pull request #158 from mjibson/offset-rows

Add support for OFFSET without the ROWS keyword (a MySQL quirk, documented at https://dev.mysql.com/doc/refman/8.0/en/select.html)

Teach the parser to remember which variant it saw (ROWS/ROW/none).

src/ast/mod.rs

@@ -26,8 +26,8 @@ pub use self::ddl::{
 };
 pub use self::operator::{BinaryOperator, UnaryOperator};
 pub use self::query::{
-    Cte, Fetch, Join, JoinConstraint, JoinOperator, OrderByExpr, Query, Select, SelectItem,
-    SetExpr, SetOperator, TableAlias, TableFactor, TableWithJoins, Top, Values,
+    Cte, Fetch, Join, JoinConstraint, JoinOperator, Offset, OffsetRows, OrderByExpr, Query, Select,
+    SelectItem, SetExpr, SetOperator, TableAlias, TableFactor, TableWithJoins, Top, Values,
 };
 pub use self::value::{DateTimeField, Value};
 

src/ast/query.rs

@@ -24,8 +24,8 @@ pub struct Query {
     pub order_by: Vec<OrderByExpr>,
     /// `LIMIT { <N> | ALL }`
     pub limit: Option<Expr>,
-    /// `OFFSET <N> { ROW | ROWS }`
-    pub offset: Option<Expr>,
+    /// `OFFSET <N> [ { ROW | ROWS } ]`
+    pub offset: Option<Offset>,
     /// `FETCH { FIRST | NEXT } <N> [ PERCENT ] { ROW | ROWS } | { ONLY | WITH TIES }`
     pub fetch: Option<Fetch>,
 }
@@ -43,7 +43,7 @@ impl fmt::Display for Query {
             write!(f, " LIMIT {}", limit)?;
         }
         if let Some(ref offset) = self.offset {
-            write!(f, " OFFSET {} ROWS", offset)?;
+            write!(f, " {}", offset)?;
         }
         if let Some(ref fetch) = self.fetch {
             write!(f, " {}", fetch)?;
@@ -391,6 +391,35 @@ impl fmt::Display for OrderByExpr {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Offset {
+    pub value: Expr,
+    pub rows: OffsetRows,
+}
+
+impl fmt::Display for Offset {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "OFFSET {}{}", self.value, self.rows)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum OffsetRows {
+    None,
+    Row,
+    Rows,
+}
+
+impl fmt::Display for OffsetRows {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            OffsetRows::None => Ok(()),
+            OffsetRows::Row => write!(f, " ROW"),
+            OffsetRows::Rows => write!(f, " ROWS"),
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Fetch {
     pub with_ties: bool,

src/parser.rs

@@ -1970,10 +1970,16 @@ impl Parser {
     }
 
     /// Parse an OFFSET clause
-    pub fn parse_offset(&mut self) -> Result<Expr, ParserError> {
+    pub fn parse_offset(&mut self) -> Result<Offset, ParserError> {
         let value = Expr::Value(self.parse_number_value()?);
-        self.expect_one_of_keywords(&["ROW", "ROWS"])?;
-        Ok(value)
+        let rows = if self.parse_keyword("ROW") {
+            OffsetRows::Row
+        } else if self.parse_keyword("ROWS") {
+            OffsetRows::Rows
+        } else {
+            OffsetRows::None
+        };
+        Ok(Offset { value, rows })
     }
 
     /// Parse a FETCH clause