Guard optimizer hints parsing by an explicit dialect method

Author: xitep

src/dialect/generic.rs

@@ -271,4 +271,8 @@ impl Dialect for GenericDialect {
     fn supports_select_format(&self) -> bool {
         true
     }
+
+    fn supports_comment_optimizer_hint(&self) -> bool {
+        true
+    }
 }

src/dialect/mod.rs

@@ -1322,6 +1322,16 @@ pub trait Dialect: Debug + Any {
         false
     }
 
+    /// Returns `true` if the dialect supports query optimizer hints in the
+    /// format of single and multi line comments immediately following a
+    /// `SELECT`, `INSERT`, `REPLACE`, `DELETE`, or `MERGE` keyword.
+    ///
+    /// [MySQL](https://dev.mysql.com/doc/refman/8.4/en/optimizer-hints.html)
+    /// [Oracle](https://docs.oracle.com/en/database/oracle/oracle-database/19/sqlrf/Comments.html#SQLRF-GUID-D316D545-89E2-4D54-977F-FC97815CD62E)
+    fn supports_comment_optimizer_hint(&self) -> bool {
+        false
+    }
+
     /// Returns true if the dialect considers the `&&` operator as a boolean AND operator.
     fn supports_double_ampersand_operator(&self) -> bool {
         false

src/dialect/mysql.rs

@@ -182,6 +182,10 @@ impl Dialect for MySqlDialect {
     fn supports_binary_kw_as_cast(&self) -> bool {
         true
     }
+
+    fn supports_comment_optimizer_hint(&self) -> bool {
+        true
+    }
 }
 
 /// `LOCK TABLES`

src/dialect/oracle.rs

@@ -99,4 +99,8 @@ impl Dialect for OracleDialect {
     fn supports_quote_delimited_string(&self) -> bool {
         true
     }
+
+    fn supports_comment_optimizer_hint(&self) -> bool {
+        true
+    }
 }

src/parser/mod.rs

@@ -14061,39 +14061,32 @@ impl<'a> Parser<'a> {
     /// [MySQL](https://dev.mysql.com/doc/refman/8.4/en/optimizer-hints.html#optimizer-hints-overview)
     /// [Oracle](https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/Comments.html#GUID-D316D545-89E2-4D54-977F-FC97815CD62E)
     fn maybe_parse_optimizer_hint(&mut self) -> Result<Option<OptimizerHint>, ParserError> {
-        let supports_multiline = dialect_of!(self is MySqlDialect | OracleDialect | GenericDialect);
-        let supports_singleline = dialect_of!(self is OracleDialect | GenericDialect);
-        if !supports_multiline && !supports_singleline {
+        let supports_hints = self.dialect.supports_comment_optimizer_hint();
+        if !supports_hints {
             return Ok(None);
         }
         loop {
             let t = self.peek_nth_token_no_skip_ref(0);
             match &t.token {
                 Token::Whitespace(ws) => {
                     match ws {
-                        Whitespace::SingleLineComment { comment, prefix } => {
-                            return Ok(if supports_singleline && comment.starts_with("+") {
-                                let text = comment.split_at(1).1.into();
-                                let prefix = prefix.clone();
-                                self.next_token_no_skip(); // Consume the comment token
-                                Some(OptimizerHint {
-                                    text,
-                                    style: OptimizerHintStyle::SingleLine { prefix },
-                                })
-                            } else {
-                                None
-                            });
-                        }
-                        Whitespace::MultiLineComment(comment) => {
-                            return Ok(if supports_multiline && comment.starts_with("+") {
-                                let text = comment.split_at(1).1.into();
-                                self.next_token_no_skip(); // Consume the comment token
-                                Some(OptimizerHint {
-                                    text,
-                                    style: OptimizerHintStyle::MultiLine,
-                                })
-                            } else {
-                                None
+                        Whitespace::SingleLineComment { comment, .. }
+                        | Whitespace::MultiLineComment(comment) => {
+                            return Ok(match comment.strip_prefix("+") {
+                                None => None,
+                                Some(text) => {
+                                    let hint = OptimizerHint {
+                                        text: text.into(),
+                                        style: if let Whitespace::SingleLineComment { prefix, .. } = ws {
+                                            OptimizerHintStyle::SingleLine { prefix: prefix.clone() }
+                                        } else {
+                                            OptimizerHintStyle::MultiLine
+                                        }
+                                    };
+                                    // Consume the comment token
+                                    self.next_token_no_skip();
+                                    Some(hint)
+                                }
                             });
                         }
                         Whitespace::Space | Whitespace::Tab | Whitespace::Newline => {