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/frontend/src/instance.rs

@@ -554,6 +554,7 @@ pub fn check_permission(
         Statement::ShowIndex(stmt) => {
             validate_db_permission!(stmt, query_ctx);
         }
+        Statement::ShowStatus(_stmt) => {}
         Statement::DescribeTable(stmt) => {
             validate_param(stmt.name(), query_ctx)?;
         }

src/operator/src/statement.rs

@@ -263,6 +263,7 @@ impl StatementExecutor {
                 self.show_columns(show_columns, query_ctx).await
             }
             Statement::ShowIndex(show_index) => self.show_index(show_index, query_ctx).await,
+            Statement::ShowStatus(_) => self.show_status(query_ctx).await,
         }
     }
 

src/operator/src/statement/show.rs

@@ -117,6 +117,13 @@ impl StatementExecutor {
             .await
             .context(error::ExecuteStatementSnafu)
     }
+
+    #[tracing::instrument(skip_all)]
+    pub async fn show_status(&self, query_ctx: QueryContextRef) -> Result<Output> {
+        query::sql::show_status(query_ctx)
+            .await
+            .context(error::ExecuteStatementSnafu)
+    }
 }
 
 pub(crate) fn create_partitions_stmt(partitions: Vec<PartitionInfo>) -> Result<Option<Partitions>> {

src/query/src/sql.rs

@@ -564,6 +564,22 @@ pub fn show_variable(stmt: ShowVariables, query_ctx: QueryContextRef) -> Result<
     Ok(Output::new_with_record_batches(records))
 }
 
+pub async fn show_status(_query_ctx: QueryContextRef) -> Result<Output> {
+    let schema = Arc::new(Schema::new(vec![
+        ColumnSchema::new("Variable_name", ConcreteDataType::string_datatype(), false),
+        ColumnSchema::new("Value", ConcreteDataType::string_datatype(), true),
+    ]));
+    let records = RecordBatches::try_from_columns(
+        schema,
+        vec![
+            Arc::new(StringVector::from(Vec::<&str>::new())) as _,
+            Arc::new(StringVector::from(Vec::<&str>::new())) as _,
+        ],
+    )
+    .context(error::CreateRecordBatchSnafu)?;
+    Ok(Output::new_with_record_batches(records))
+}
+
 pub fn show_create_table(
     table: TableRef,
     partitions: Option<Partitions>,

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),