Change Word::keyword to a enum (#193)

This improves performance and paves the way to future API enhancements as discussed in the PR https://github.com/andygrove/sqlparser-rs/pull/193

src/ast/mod.rs

@@ -388,22 +388,6 @@ impl fmt::Display for WindowFrameUnits {
     }
 }
 
-impl FromStr for WindowFrameUnits {
-    type Err = ParserError;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        match s {
-            "ROWS" => Ok(WindowFrameUnits::Rows),
-            "RANGE" => Ok(WindowFrameUnits::Range),
-            "GROUPS" => Ok(WindowFrameUnits::Groups),
-            _ => Err(ParserError::ParserError(format!(
-                "Expected ROWS, RANGE, or GROUPS, found: {}",
-                s
-            ))),
-        }
-    }
-}
-
 /// Specifies [WindowFrame]'s `start_bound` and `end_bound`
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]

src/dialect/keywords.rs

@@ -41,12 +41,24 @@ macro_rules! define_keywords {
     ($(
         $ident:ident $(= $string_keyword:expr)?
     ),*) => {
-        $(kw_def!($ident $(= $string_keyword)?);)*
+        #[derive(Debug, Clone, Copy, PartialEq, PartialOrd, Eq, Ord)]
+        #[allow(non_camel_case_types)]
+        pub enum Keyword {
+            NoKeyword,
+            $($ident),*
+        }
 
+        pub const ALL_KEYWORDS_INDEX: &[Keyword] = &[
+            $(Keyword::$ident),*
+        ];
+
+        $(kw_def!($ident $(= $string_keyword)?);)*
         pub const ALL_KEYWORDS: &[&str] = &[
             $($ident),*
         ];
-    }
+
+    };
+
 }
 
 // The following keywords should be sorted to be able to match using binary search
@@ -434,20 +446,52 @@ define_keywords!(
 
 /// These keywords can't be used as a table alias, so that `FROM table_name alias`
 /// can be parsed unambiguously without looking ahead.
-pub const RESERVED_FOR_TABLE_ALIAS: &[&str] = &[
+pub const RESERVED_FOR_TABLE_ALIAS: &[Keyword] = &[
     // Reserved as both a table and a column alias:
-    WITH, SELECT, WHERE, GROUP, HAVING, ORDER, TOP, LIMIT, OFFSET, FETCH, UNION, EXCEPT, INTERSECT,
+    Keyword::WITH,
+    Keyword::SELECT,
+    Keyword::WHERE,
+    Keyword::GROUP,
+    Keyword::HAVING,
+    Keyword::ORDER,
+    Keyword::TOP,
+    Keyword::LIMIT,
+    Keyword::OFFSET,
+    Keyword::FETCH,
+    Keyword::UNION,
+    Keyword::EXCEPT,
+    Keyword::INTERSECT,
     // Reserved only as a table alias in the `FROM`/`JOIN` clauses:
-    ON, JOIN, INNER, CROSS, FULL, LEFT, RIGHT, NATURAL, USING,
+    Keyword::ON,
+    Keyword::JOIN,
+    Keyword::INNER,
+    Keyword::CROSS,
+    Keyword::FULL,
+    Keyword::LEFT,
+    Keyword::RIGHT,
+    Keyword::NATURAL,
+    Keyword::USING,
     // for MSSQL-specific OUTER APPLY (seems reserved in most dialects)
-    OUTER,
+    Keyword::OUTER,
 ];
 
 /// Can't be used as a column alias, so that `SELECT <expr> alias`
 /// can be parsed unambiguously without looking ahead.
-pub const RESERVED_FOR_COLUMN_ALIAS: &[&str] = &[
+pub const RESERVED_FOR_COLUMN_ALIAS: &[Keyword] = &[
     // Reserved as both a table and a column alias:
-    WITH, SELECT, WHERE, GROUP, HAVING, ORDER, LIMIT, OFFSET, FETCH, UNION, EXCEPT, INTERSECT,
-    // Reserved only as a column alias in the `SELECT` clause:
-    FROM,
+    Keyword::WITH,
+    Keyword::SELECT,
+    Keyword::WHERE,
+    Keyword::GROUP,
+    Keyword::HAVING,
+    Keyword::ORDER,
+    Keyword::TOP,
+    Keyword::LIMIT,
+    Keyword::OFFSET,
+    Keyword::FETCH,
+    Keyword::UNION,
+    Keyword::EXCEPT,
+    Keyword::INTERSECT,
+    // Reserved only as a column alias in the `SELECT` clause
+    Keyword::FROM,
 ];

src/tokenizer.rs

@@ -19,7 +19,7 @@
 use std::iter::Peekable;
 use std::str::Chars;
 
-use super::dialect::keywords::ALL_KEYWORDS;
+use super::dialect::keywords::{Keyword, ALL_KEYWORDS, ALL_KEYWORDS_INDEX};
 use super::dialect::Dialect;
 use std::fmt;
 
@@ -146,15 +146,14 @@ impl Token {
     }
     pub fn make_word(word: &str, quote_style: Option<char>) -> Self {
         let word_uppercase = word.to_uppercase();
-        let is_keyword =
-            quote_style == None && ALL_KEYWORDS.binary_search(&word_uppercase.as_str()).is_ok();
         Token::Word(Word {
             value: word.to_string(),
             quote_style,
-            keyword: if is_keyword {
-                word_uppercase
+            keyword: if quote_style == None {
+                let keyword = ALL_KEYWORDS.binary_search(&word_uppercase.as_str());
+                keyword.map_or(Keyword::NoKeyword, |x| ALL_KEYWORDS_INDEX[x])
             } else {
-                "".to_string()
+                Keyword::NoKeyword
             },
         })
     }
@@ -172,7 +171,7 @@ pub struct Word {
     pub quote_style: Option<char>,
     /// If the word was not quoted and it matched one of the known keywords,
     /// this will have one of the values from dialect::keywords, otherwise empty
-    pub keyword: String,
+    pub keyword: Keyword,
 }
 
 impl fmt::Display for Word {

tests/sqlparser_common.rs

@@ -22,7 +22,7 @@ use matches::assert_matches;
 
 use sqlparser::ast::*;
 use sqlparser::dialect::keywords::ALL_KEYWORDS;
-use sqlparser::parser::*;
+use sqlparser::parser::{Parser, ParserError};
 use sqlparser::test_utils::{all_dialects, expr_from_projection, number, only};
 
 #[test]
@@ -1354,10 +1354,12 @@ fn parse_window_functions() {
                avg(bar) OVER (ORDER BY a \
                RANGE BETWEEN 1 PRECEDING AND 1 FOLLOWING), \
                max(baz) OVER (ORDER BY a \
-               ROWS UNBOUNDED PRECEDING) \
+               ROWS UNBOUNDED PRECEDING), \
+               sum(qux) OVER (ORDER BY a \
+               GROUPS BETWEEN 1 PRECEDING AND 1 FOLLOWING) \
                FROM foo";
     let select = verified_only_select(sql);
-    assert_eq!(4, select.projection.len());
+    assert_eq!(5, select.projection.len());
     assert_eq!(
         &Expr::Function(Function {
             name: ObjectName(vec![Ident::new("row_number")]),
@@ -2872,7 +2874,7 @@ fn parse_drop_index() {
 }
 
 #[test]
-fn keywords_sorted() {
+fn all_keywords_sorted() {
     // assert!(ALL_KEYWORDS.is_sorted())
     let mut copy = Vec::from(ALL_KEYWORDS);
     copy.sort();