feat: impl select (grpc) (#138)

* SelectExpr: change to oneof expr

* Convert between Vec<u8> and SelectResult

* Chore: use encode_to_vec and decode, instead of encode_length_delimited_to_vec and decode_length_delimited

* Chore: move bitset into separate file

* Grpc select impl

src/client/examples/insert.rs

@@ -1,15 +1,19 @@
-use api::v1::*;
+use api::v1::{codec::InsertBatch, *};
 use client::{Client, Database};
 
-#[tokio::main]
-async fn main() {
-    let url = "http://127.0.0.1:3001";
-    let db_name = "db";
-    let table_name = "demo";
+fn main() {
+    tracing::subscriber::set_global_default(tracing_subscriber::FmtSubscriber::builder().finish())
+        .unwrap();
 
-    let client = Client::connect(url).await.unwrap();
-    let db = Database::new(db_name, client);
-    db.insert(table_name, insert_batches()).await.unwrap();
+    run();
+}
+
+#[tokio::main]
+async fn run() {
+    let client = Client::connect("http://127.0.0.1:3001").await.unwrap();
+    let db = Database::new("greptime", client);
+
+    db.insert("demo", insert_batches()).await.unwrap();
 }
 
 fn insert_batches() -> Vec<Vec<u8>> {

src/client/examples/select.rs

@@ -0,0 +1,23 @@
+use api::v1::{select_expr, SelectExpr};
+use client::{Client, Database};
+use tracing::{event, Level};
+
+fn main() {
+    tracing::subscriber::set_global_default(tracing_subscriber::FmtSubscriber::builder().finish())
+        .unwrap();
+
+    run();
+}
+
+#[tokio::main]
+async fn run() {
+    let client = Client::connect("http://127.0.0.1:3001").await.unwrap();
+    let db = Database::new("greptime", client);
+
+    let select_expr = SelectExpr {
+        expr: Some(select_expr::Expr::Sql("select * from demo".to_string())),
+    };
+    let result = db.select(select_expr).await.unwrap();
+
+    event!(Level::INFO, "result: {:#?}", result);
+}