feat: add the system.queries table (influxdata#24992)

The system.queries table is now accessible, when queries are initiated
in debug mode, which is not currently enabled via the HTTP API, therefore
this is not yet accessible unless via the gRPC interface.

The system.queries table lists all queries in the QueryLog on the
QueryExecutorImpl.

influxdb3/src/commands/serve.rs

@@ -156,6 +156,17 @@ pub struct Config {
         action
     )]
     pub segment_duration: SegmentDuration,
+
+    // TODO - tune this default:
+    /// The size of the query log. Up to this many queries will remain in the log before
+    /// old queries are evicted to make room for new ones.
+    #[clap(
+        long = "query-log-size",
+        env = "INFLUXDB3_QUERY_LOG_SIZE",
+        default_value = "1000",
+        action
+    )]
+    pub query_log_size: usize,
 }
 
 /// If `p` does not exist, try to create it as a directory.
@@ -275,6 +286,7 @@ pub async fn command(config: Config) -> Result<()> {
         Arc::clone(&metrics),
         Arc::new(config.datafusion_config),
         10,
+        config.query_log_size,
     ));
 
     let builder = ServerBuilder::new(common_state)

influxdb3/tests/server/main.rs

@@ -17,6 +17,7 @@ mod flight;
 mod limits;
 mod ping;
 mod query;
+mod system_tables;
 mod write;
 
 /// Configuration for a [`TestServer`]
@@ -115,14 +116,24 @@ impl TestServer {
 
     /// Get a [`FlightSqlClient`] for making requests to the running service over gRPC
     pub async fn flight_sql_client(&self, database: &str) -> FlightSqlClient {
+        self.flight_sql_client_debug_mode(database, false).await
+    }
+
+    pub async fn flight_sql_client_debug_mode(
+        &self,
+        database: &str,
+        debug_mode: bool,
+    ) -> FlightSqlClient {
         let channel = tonic::transport::Channel::from_shared(self.client_addr())
             .expect("create tonic channel")
             .connect()
             .await
             .expect("connect to gRPC client");
         let mut client = FlightSqlClient::new(channel);
         client.add_header("database", database).unwrap();
-        client.add_header("iox-debug", "true").unwrap();
+        if debug_mode {
+            client.add_header("iox-debug", "true").unwrap();
+        }
         client
     }