feat: Implement SHOW STATUS (#4050)

* show status returning empty contents

* return an empty set instead of affected rows

* chore: Update src/query/src/sql.rs

---------

Co-authored-by: Yingwen <realevenyag@gmail.com>

src/sql/src/parsers/show_parser.rs

@@ -19,7 +19,8 @@ use sqlparser::tokenizer::Token;
 use crate::error::{self, InvalidDatabaseNameSnafu, InvalidTableNameSnafu, Result};
 use crate::parser::ParserContext;
 use crate::statements::show::{
-    ShowColumns, ShowCreateTable, ShowDatabases, ShowIndex, ShowKind, ShowTables, ShowVariables,
+    ShowColumns, ShowCreateTable, ShowDatabases, ShowIndex, ShowKind, ShowStatus, ShowTables,
+    ShowVariables,
 };
 use crate::statements::statement::Statement;
 
@@ -82,6 +83,8 @@ impl<'a> ParserContext<'a> {
                     actual: self.peek_token_as_string(),
                 })?;
             Ok(Statement::ShowVariables(ShowVariables { variable }))
+        } else if self.consume_token("STATUS") {
+            Ok(Statement::ShowStatus(ShowStatus {}))
         } else {
             self.unsupported(self.peek_token_as_string())
         }

src/sql/src/statements/show.rs

@@ -145,6 +145,16 @@ impl Display for ShowVariables {
     }
 }
 
+/// SQL structure for "SHOW STATUS"
+#[derive(Debug, Clone, PartialEq, Eq, Visit, VisitMut)]
+pub struct ShowStatus {}
+
+impl Display for ShowStatus {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "SHOW STATUS")
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use std::assert_matches::assert_matches;

src/sql/src/statements/statement.rs

@@ -31,7 +31,8 @@ use crate::statements::insert::Insert;
 use crate::statements::query::Query;
 use crate::statements::set_variables::SetVariables;
 use crate::statements::show::{
-    ShowColumns, ShowCreateTable, ShowDatabases, ShowIndex, ShowKind, ShowTables, ShowVariables,
+    ShowColumns, ShowCreateTable, ShowDatabases, ShowIndex, ShowKind, ShowStatus, ShowTables,
+    ShowVariables,
 };
 use crate::statements::tql::Tql;
 use crate::statements::truncate::TruncateTable;
@@ -80,6 +81,8 @@ pub enum Statement {
     ShowIndex(ShowIndex),
     // SHOW CREATE TABLE
     ShowCreateTable(ShowCreateTable),
+    // SHOW STATUS
+    ShowStatus(ShowStatus),
     // DESCRIBE TABLE
     DescribeTable(DescribeTable),
     // EXPLAIN QUERY
@@ -115,6 +118,7 @@ impl Display for Statement {
             Statement::ShowColumns(s) => s.fmt(f),
             Statement::ShowIndex(s) => s.fmt(f),
             Statement::ShowCreateTable(s) => s.fmt(f),
+            Statement::ShowStatus(s) => s.fmt(f),
             Statement::DescribeTable(s) => s.fmt(f),
             Statement::Explain(s) => s.fmt(f),
             Statement::Copy(s) => s.fmt(f),