Support parsing multiple show variables. (apache#290)

* feat: support parsing multiple show variables.

* fix: fix fmt error

Author: francis-du

src/ast/mod.rs

@@ -637,7 +637,7 @@ pub enum Statement {
     /// SHOW <variable>
     ///
     /// Note: this is a PostgreSQL-specific statement.
-    ShowVariable { variable: Ident },
+    ShowVariable { variable: Vec<Ident> },
     /// SHOW COLUMNS
     ///
     /// Note: this is a MySQL-specific statement.
@@ -1136,7 +1136,13 @@ impl fmt::Display for Statement {
                     value = display_comma_separated(value)
                 )
             }
-            Statement::ShowVariable { variable } => write!(f, "SHOW {}", variable),
+            Statement::ShowVariable { variable } => {
+                write!(f, "SHOW")?;
+                if !variable.is_empty() {
+                    write!(f, " {}", display_separated(variable, " "))?;
+                }
+                Ok(())
+            }
             Statement::ShowColumns {
                 extended,
                 full,

src/parser.rs

@@ -2043,6 +2043,19 @@ impl<'a> Parser<'a> {
         Ok(ObjectName(idents))
     }
 
+    /// Parse identifiers
+    pub fn parse_identifiers(&mut self) -> Result<Vec<Ident>, ParserError> {
+        let mut idents = vec![];
+        loop {
+            match self.next_token() {
+                Token::Word(w) => idents.push(w.to_ident()),
+                Token::EOF => break,
+                _ => {}
+            }
+        }
+        Ok(idents)
+    }
+
     /// Parse a simple one-word identifier (possibly quoted, possibly a keyword)
     pub fn parse_identifier(&mut self) -> Result<Ident, ParserError> {
         match self.next_token() {
@@ -2439,7 +2452,7 @@ impl<'a> Parser<'a> {
             self.parse_show_columns()
         } else {
             Ok(Statement::ShowVariable {
-                variable: self.parse_identifier()?,
+                variable: self.parse_identifiers()?,
             })
         }
     }

tests/sqlparser_postgres.rs

@@ -443,19 +443,19 @@ fn parse_set() {
 
 #[test]
 fn parse_show() {
-    let stmt = pg_and_generic().verified_stmt("SHOW a");
+    let stmt = pg_and_generic().verified_stmt("SHOW a a");
     assert_eq!(
         stmt,
         Statement::ShowVariable {
-            variable: "a".into()
+            variable: vec!["a".into(), "a".into()]
         }
     );
 
-    let stmt = pg_and_generic().verified_stmt("SHOW ALL");
+    let stmt = pg_and_generic().verified_stmt("SHOW ALL ALL");
     assert_eq!(
         stmt,
         Statement::ShowVariable {
-            variable: "ALL".into()
+            variable: vec!["ALL".into(), "ALL".into()]
         }
     )
 }