add set time zone sometimezone as a exception while parsing keyword::set (#727)

* add set time zone sometimezone as a exception while parsing keyword::set

* remove redundant parentheses

* add Statement::SetTimeZone

* delete useless comments

src/ast/mod.rs

@@ -1271,6 +1271,11 @@ pub enum Statement {
         variable: ObjectName,
         value: Vec<Expr>,
     },
+    /// SET TIME ZONE <value>
+    ///
+    /// Note: this is a PostgreSQL-specific statements
+    /// SET TIME ZONE <value> is an alias for SET timezone TO <value> in PostgreSQL
+    SetTimeZone { local: bool, value: Expr },
     /// SET NAMES 'charset_name' [COLLATE 'collation_name']
     ///
     /// Note: this is a MySQL-specific statement.
@@ -2228,6 +2233,13 @@ impl fmt::Display for Statement {
                     value = display_comma_separated(value)
                 )
             }
+            Statement::SetTimeZone { local, value } => {
+                f.write_str("SET ")?;
+                if *local {
+                    f.write_str("LOCAL ")?;
+                }
+                write!(f, "TIME ZONE {value}")
+            }
             Statement::SetNames {
                 charset_name,
                 collation_name,

src/parser.rs

@@ -4551,6 +4551,15 @@ impl<'a> Parser<'a> {
                     value: values,
                 });
             }
+        } else if variable.to_string().eq_ignore_ascii_case("TIMEZONE") {
+            // for some db (e.g. postgresql), SET TIME ZONE <value> is an alias for SET TIMEZONE [TO|=] <value>
+            match self.parse_expr() {
+                Ok(expr) => Ok(Statement::SetTimeZone {
+                    local: modifier == Some(Keyword::LOCAL),
+                    value: expr,
+                }),
+                _ => self.expected("timezone value", self.peek_token())?,
+            }
         } else if variable.to_string() == "CHARACTERISTICS" {
             self.expect_keywords(&[Keyword::AS, Keyword::TRANSACTION])?;
             Ok(Statement::SetTransaction {

tests/sqlparser_common.rs

@@ -4979,6 +4979,17 @@ fn parse_set_time_zone() {
     one_statement_parses_to("SET TIME ZONE TO 'UTC'", "SET TIMEZONE = 'UTC'");
 }
 
+#[test]
+fn parse_set_time_zone_alias() {
+    match verified_stmt("SET TIME ZONE 'UTC'") {
+        Statement::SetTimeZone { local, value } => {
+            assert!(!local);
+            assert_eq!(value, Expr::Value(Value::SingleQuotedString("UTC".into())));
+        }
+        _ => unreachable!(),
+    }
+}
+
 #[test]
 fn parse_commit() {
     match verified_stmt("COMMIT") {