fix: support prepared query option SHOW without changing compatibility

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

src/servers/src/mysql/federated.rs

@@ -281,10 +281,10 @@ fn check_show_variables(query: &str) -> Option<Output> {
     } else if SHOW_LOWER_CASE_PATTERN.is_match(query) {
         Some(show_variables("lower_case_table_names", "0"))
     } else if let Some(matched) = SHOW_VARIABLES_LIKE_PATTERN.find(query) {
-        let remainder = &query[matched.end()..];
-        let remainder = strip_leading_comments(remainder).trim_start();
-        let remainder = remainder.strip_prefix(';').unwrap_or(remainder);
-        let remainder = strip_leading_comments(remainder);
+        let mut remainder = strip_leading_comments(&query[matched.end()..]);
+        while let Some(rest) = remainder.strip_prefix(';') {
+            remainder = strip_leading_comments(rest);
+        }
         if remainder.is_empty() {
             Some(show_variables("", ""))
         } else {
@@ -668,6 +668,7 @@ mod test {
             "SHOW VARIABLES query.parallelism;",
             "SHOW VARIABLES /* comment */ query.parallelism",
             "SHOW VARIABLES; SELECT 1",
+            "SHOW VARIABLES; /* comment */; SELECT 1",
         ] {
             assert!(
                 check(query, QueryContext::arc(), session.clone()).is_none(),
@@ -678,6 +679,8 @@ mod test {
         for query in [
             "SHOW VARIABLES",
             "SHOW VARIABLES;",
+            "SHOW VARIABLES;;",
+            "SHOW VARIABLES; /* comment */;",
             "SHOW VARIABLES /* comment */",
             "SHOW VARIABLES /* comment */;",
             "SHOW VARIABLES # comment",

src/servers/src/postgres/handler.rs

@@ -355,7 +355,7 @@ impl QueryParser for DefaultQueryParser {
         let (sql, copy_to_stdout_format) = if let Ok(mut statements) = parsed_statements {
             let first_stmt = statements.remove(0);
             let format = check_copy_to_stdout(&first_stmt);
-            (first_stmt.to_string(), format)
+            (statement_to_query(&first_stmt), format)
         } else {
             // bypass the error: it can run into error because of different
             // versions of sqlparser

src/servers/tests/postgres/mod.rs

@@ -551,6 +551,24 @@ async fn test_extended_query_regproc_response() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn test_extended_query_show_query_option() -> Result<()> {
+    let server_port = start_test_server(TlsOption::default()).await?;
+    let client = create_connection_with_given_db(server_port, DEFAULT_SCHEMA_NAME)
+        .await
+        .unwrap();
+    client
+        .batch_execute("SET query.parallelism = 2")
+        .await
+        .unwrap();
+    let statement = client.prepare("SHOW query.parallelism").await.unwrap();
+    let rows = client.query(&statement, &[]).await.unwrap();
+    assert_eq!(rows.len(), 1);
+    assert_eq!(rows[0].get::<usize, String>(0), "2");
+
+    Ok(())
+}
+
 #[tokio::test]
 async fn test_extended_query() -> Result<()> {
     let server_port = start_test_server(TlsOption::default()).await?;