Support SHOW FUNCTIONS (#620)

* support SHOW FUNCTIONS

* Update keywords.rs

* Update mod.rs

* Update sqlparser_common.rs

* Fix CI issues

Author: joocer

src/ast/mod.rs

@@ -1144,6 +1144,10 @@ pub enum Statement {
     ///
     /// Note: this is a MySQL-specific statement.
     SetNamesDefault {},
+    /// SHOW FUNCTIONS 
+    ///
+    /// Note: this is a Presto-specific statement.
+    ShowFunctions { filter: Option<ShowStatementFilter> },
     /// SHOW <variable>
     ///
     /// Note: this is a PostgreSQL-specific statement.
@@ -2033,6 +2037,13 @@ impl fmt::Display for Statement {
                 }
                 Ok(())
             }
+            Statement::ShowFunctions { filter } => {
+                write!(f, "SHOW FUNCTIONS")?;
+                if let Some(filter) = filter {
+                    write!(f, " {}", filter)?;
+                }
+                Ok(())
+            }
             Statement::Use { db_name } => {
                 write!(f, "USE {}", db_name)?;
                 Ok(())

src/keywords.rs

@@ -250,6 +250,7 @@ define_keywords!(
     FROM,
     FULL,
     FUNCTION,
+    FUNCTIONS,
     FUSION,
     GET,
     GLOBAL,

src/parser.rs

@@ -3854,6 +3854,8 @@ impl<'a> Parser<'a> {
             Ok(self.parse_show_columns(extended, full)?)
         } else if self.parse_keyword(Keyword::TABLES) {
             Ok(self.parse_show_tables(extended, full)?)
+        } else if self.parse_keyword(Keyword::FUNCTIONS) {
+            Ok(self.parse_show_functions()?)
         } else if extended || full {
             Err(ParserError::ParserError(
                 "EXTENDED/FULL are not supported with this type of SHOW query".to_string(),
@@ -3945,6 +3947,11 @@ impl<'a> Parser<'a> {
         })
     }
 
+    pub fn parse_show_functions(&mut self) -> Result<Statement, ParserError> {
+        let filter = self.parse_show_statement_filter()?;
+        Ok(Statement::ShowFunctions { filter })
+    }
+
     pub fn parse_show_collation(&mut self) -> Result<Statement, ParserError> {
         let filter = self.parse_show_statement_filter()?;
         Ok(Statement::ShowCollation { filter })

tests/sqlparser_common.rs

@@ -5569,3 +5569,13 @@ fn parse_cursor() {
         _ => unreachable!(),
     }
 }
+
+#[test]
+fn parse_show_functions() {
+    assert_eq!(
+        verified_stmt("SHOW FUNCTIONS LIKE 'pattern'"),
+        Statement::ShowFunctions {
+            filter: Some(ShowStatementFilter::Like("pattern".into())),
+        }
+    );
+}