Support snowflake double dot notation for object name (apache#1540)

src/dialect/mod.rs

@@ -365,6 +365,16 @@ pub trait Dialect: Debug + Any {
         self.supports_trailing_commas()
     }
 
+    /// Returns true if the dialect supports double dot notation for object names
+    ///
+    /// Example
+    /// ```sql
+    /// SELECT * FROM db_name..table_name
+    /// ```
+    fn supports_object_name_double_dot_notation(&self) -> bool {
+        false
+    }
+
     /// Dialect-specific infix parser override
     ///
     /// This method is called to parse the next infix expression.

src/dialect/snowflake.rs

@@ -54,6 +54,14 @@ impl Dialect for SnowflakeDialect {
         true
     }
 
+    // Snowflake supports double-dot notation when the schema name is not specified
+    // In this case the default PUBLIC schema is used
+    //
+    // see https://docs.snowflake.com/en/sql-reference/name-resolution#resolution-when-schema-omitted-double-dot-notation
+    fn supports_object_name_double_dot_notation(&self) -> bool {
+        true
+    }
+
     fn is_identifier_part(&self, ch: char) -> bool {
         ch.is_ascii_lowercase()
             || ch.is_ascii_uppercase()

src/parser/mod.rs

@@ -8457,6 +8457,13 @@ impl<'a> Parser<'a> {
     pub fn parse_object_name(&mut self, in_table_clause: bool) -> Result<ObjectName, ParserError> {
         let mut idents = vec![];
         loop {
+            if self.dialect.supports_object_name_double_dot_notation()
+                && idents.len() == 1
+                && self.consume_token(&Token::Period)
+            {
+                // Empty string here means default schema
+                idents.push(Ident::new(""));
+            }
             idents.push(self.parse_identifier(in_table_clause)?);
             if !self.consume_token(&Token::Period) {
                 break;

tests/sqlparser_snowflake.rs

@@ -2866,3 +2866,35 @@ fn test_projection_with_nested_trailing_commas() {
     let sql = "SELECT a, b, FROM c, (SELECT d, e, FROM f, LATERAL FLATTEN(input => events))";
     let _ = snowflake().parse_sql_statements(sql).unwrap();
 }
+
+#[test]
+fn test_sf_double_dot_notation() {
+    snowflake().verified_stmt("SELECT * FROM db_name..table_name");
+    snowflake().verified_stmt("SELECT * FROM x, y..z JOIN a..b AS b ON x.id = b.id");
+
+    assert_eq!(
+        snowflake()
+            .parse_sql_statements("SELECT * FROM X.Y..")
+            .unwrap_err()
+            .to_string(),
+        "sql parser error: Expected: identifier, found: ."
+    );
+    assert_eq!(
+        snowflake()
+            .parse_sql_statements("SELECT * FROM X..Y..Z")
+            .unwrap_err()
+            .to_string(),
+        "sql parser error: Expected: identifier, found: ."
+    );
+    assert_eq!(
+        // Ensure we don't parse leading token
+        snowflake()
+            .parse_sql_statements("SELECT * FROM .X.Y")
+            .unwrap_err()
+            .to_string(),
+        "sql parser error: Expected: identifier, found: ."
+    );
+}
+
+#[test]
+fn test_parse_double_dot_notation_wrong_position() {}