feat: frontend instance (#238)

* feat: frontend instance

* no need to carry column length in `Column` proto

* add more tests

* rebase develop

* create a new variant with already provisioned RecordBatches in Output

* resolve code review comments

* new frontend instance does not connect datanode grpc

* add more tests

* add more tests

* rebase develop

Co-authored-by: luofucong <luofucong@greptime.com>

src/servers/src/error.rs

@@ -65,6 +65,12 @@ pub enum Error {
 
     #[snafu(display("Not supported: {}", feat))]
     NotSupported { feat: String },
+
+    #[snafu(display("Invalid query: {}", reason))]
+    InvalidQuery {
+        reason: String,
+        backtrace: Backtrace,
+    },
 }
 
 pub type Result<T> = std::result::Result<T, Error>;
@@ -86,7 +92,7 @@ impl ErrorExt for Error {
             | ExecuteScript { source, .. }
             | ExecuteQuery { source, .. } => source.status_code(),
 
-            NotSupported { .. } => StatusCode::InvalidArguments,
+            NotSupported { .. } | InvalidQuery { .. } => StatusCode::InvalidArguments,
         }
     }
 

src/servers/src/http.rs

@@ -81,10 +81,13 @@ impl JsonResponse {
             Ok(Output::AffectedRows(rows)) => {
                 Self::with_output(Some(JsonOutput::AffectedRows(rows)))
             }
-            Ok(Output::RecordBatch(stream)) => match util::collect(stream).await {
+            Ok(Output::Stream(stream)) => match util::collect(stream).await {
                 Ok(rows) => Self::with_output(Some(JsonOutput::Rows(rows))),
                 Err(e) => Self::with_error(Some(format!("Recordbatch error: {}", e))),
             },
+            Ok(Output::RecordBatches(recordbatches)) => {
+                Self::with_output(Some(JsonOutput::Rows(recordbatches.to_vec())))
+            }
             Err(e) => Self::with_error(Some(format!("Query engine output error: {}", e))),
         }
     }

src/servers/src/mysql/writer.rs

@@ -34,7 +34,7 @@ impl<'a, W: io::Write> MysqlResultWriter<'a, W> {
         })?;
         match output {
             Ok(output) => match output {
-                Output::RecordBatch(stream) => {
+                Output::Stream(stream) => {
                     let schema = stream.schema().clone();
                     let recordbatches = util::collect(stream)
                         .await
@@ -45,6 +45,13 @@ impl<'a, W: io::Write> MysqlResultWriter<'a, W> {
                     };
                     Self::write_query_result(query_result, writer)?
                 }
+                Output::RecordBatches(recordbatches) => {
+                    let query_result = QueryResult {
+                        schema: recordbatches.schema(),
+                        recordbatches: recordbatches.to_vec(),
+                    };
+                    Self::write_query_result(query_result, writer)?
+                }
                 Output::AffectedRows(rows) => Self::write_affected_rows(writer, rows)?,
             },
             Err(error) => Self::write_query_error(error, writer)?,