Remove ClusterHelper in planner

Signed-off-by: Xuanwo <github@xuanwo.io>

Author: Xuanwo

src/query/catalog/src/cluster_info.rs

@@ -20,3 +20,17 @@ pub struct Cluster {
     pub local_id: String,
     pub nodes: Vec<Arc<NodeInfo>>,
 }
+
+impl Cluster {
+    /// If this cluster is empty?
+    ///
+    /// # TODO
+    ///
+    /// From @Xuanwo
+    ///
+    /// Ideally, we should implement a cluster trait to replace `ClusterHelper`
+    /// defined in `databend-query`.
+    pub fn is_empty(&self) -> bool {
+        self.nodes.is_empty()
+    }
+}

src/query/service/src/interpreters/interpreter_select.rs

@@ -19,7 +19,6 @@ use common_exception::Result;
 use common_legacy_planners::PlanNode;
 use common_legacy_planners::SelectPlan;
 
-use crate::clusters::ClusterHelper;
 use crate::interpreters::plan_schedulers;
 use crate::interpreters::Interpreter;
 use crate::optimizers::Optimizers;

src/query/service/src/interpreters/interpreter_select_v2.rs

@@ -18,7 +18,6 @@ use common_datavalues::DataSchemaRef;
 use common_exception::Result;
 
 use super::plan_schedulers::schedule_query_v2;
-use crate::clusters::ClusterHelper;
 use crate::interpreters::Interpreter;
 use crate::pipelines::PipelineBuildResult;
 use crate::sessions::QueryContext;

src/query/service/src/optimizers/optimizer_scatters.rs

@@ -34,7 +34,6 @@ use common_legacy_planners::StagePlan;
 use common_legacy_planners::WindowFuncPlan;
 use enum_extract::let_extract;
 
-use crate::clusters::ClusterHelper;
 use crate::optimizers::Optimizer;
 use crate::sessions::QueryContext;
 use crate::sessions::TableContext;

src/query/service/src/sql/planner/binder/insert.rs

@@ -21,7 +21,6 @@ use common_datavalues::DataSchemaRefExt;
 use common_exception::Result;
 use tracing::debug;
 
-use crate::clusters::ClusterHelper;
 use crate::sql::binder::Binder;
 use crate::sql::normalize_identifier;
 use crate::sql::optimizer::optimize;

src/query/service/src/sql/planner/mod.rs

@@ -23,7 +23,6 @@ use common_exception::Result;
 use parking_lot::RwLock;
 pub use plans::ScalarExpr;
 
-use crate::clusters::ClusterHelper;
 use crate::sql::optimizer::optimize;
 pub use crate::sql::planner::binder::BindContext;