feat: cache logical region's metadata

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>

src/metric-engine/src/engine/alter.rs

@@ -64,15 +64,19 @@ impl MetricEngineInner {
     /// Return the physical region id behind this logical region
     async fn alter_logical_region(
         &self,
-        region_id: RegionId,
+        logical_region_id: RegionId,
         request: RegionAlterRequest,
     ) -> Result<RegionId> {
         let physical_region_id = {
             let state = &self.state.read().unwrap();
-            state.get_physical_region_id(region_id).with_context(|| {
-                error!("Trying to alter an nonexistent region {region_id}");
-                LogicalRegionNotFoundSnafu { region_id }
-            })?
+            state
+                .get_physical_region_id(logical_region_id)
+                .with_context(|| {
+                    error!("Trying to alter an nonexistent region {logical_region_id}");
+                    LogicalRegionNotFoundSnafu {
+                        region_id: logical_region_id,
+                    }
+                })?
         };
 
         // only handle adding column
@@ -87,7 +91,7 @@ impl MetricEngineInner {
                 .metadata_region
                 .column_semantic_type(
                     metadata_region_id,
-                    region_id,
+                    logical_region_id,
                     &col.column_metadata.column_schema.name,
                 )
                 .await?
@@ -102,18 +106,24 @@ impl MetricEngineInner {
         self.add_columns_to_physical_data_region(
             data_region_id,
             metadata_region_id,
-            region_id,
+            logical_region_id,
             columns_to_add,
         )
         .await?;
 
         // register columns to logical region
         for col in columns {
             self.metadata_region
-                .add_column(metadata_region_id, region_id, &col.column_metadata)
+                .add_column(metadata_region_id, logical_region_id, &col.column_metadata)
                 .await?;
         }
 
+        // invalid logical column cache
+        self.state
+            .write()
+            .unwrap()
+            .invalid_logical_column_cache(logical_region_id);
+
         Ok(physical_region_id)
     }
 

src/metric-engine/src/engine/read.rs

@@ -169,11 +169,11 @@ impl MetricEngineInner {
     ) -> Result<Vec<usize>> {
         // project on logical columns
         let all_logical_columns = self
-            .load_logical_columns(physical_region_id, logical_region_id)
+            .load_logical_column_names(physical_region_id, logical_region_id)
             .await?;
         let projected_logical_names = origin_projection
             .iter()
-            .map(|i| all_logical_columns[*i].column_schema.name.clone())
+            .map(|i| all_logical_columns[*i].clone())
             .collect::<Vec<_>>();
 
         // generate physical projection
@@ -200,10 +200,8 @@ impl MetricEngineInner {
         logical_region_id: RegionId,
     ) -> Result<Vec<usize>> {
         let logical_columns = self
-            .load_logical_columns(physical_region_id, logical_region_id)
-            .await?
-            .into_iter()
-            .map(|col| col.column_schema.name);
+            .load_logical_column_names(physical_region_id, logical_region_id)
+            .await?;
         let mut projection = Vec::with_capacity(logical_columns.len());
         let data_region_id = utils::to_data_region_id(physical_region_id);
         let physical_metadata = self

src/metric-engine/src/engine/region_metadata.rs

@@ -23,25 +23,74 @@ use crate::error::Result;
 impl MetricEngineInner {
     /// Load column metadata of a logical region.
     ///
-    /// The return value is ordered on [ColumnId].
+    /// The return value is ordered on column name.
     pub async fn load_logical_columns(
         &self,
         physical_region_id: RegionId,
         logical_region_id: RegionId,
     ) -> Result<Vec<ColumnMetadata>> {
-        // load logical and physical columns, and intersect them to get logical column metadata
+        // First try to load from state cache
+        if let Some(columns) = self
+            .state
+            .read()
+            .unwrap()
+            .logical_columns()
+            .get(&logical_region_id)
+        {
+            return Ok(columns.clone());
+        }
+
+        // Else load from metadata region and update the cache.
+        // Load logical and physical columns, and intersect them to get logical column metadata.
         let mut logical_column_metadata = self
             .metadata_region
             .logical_columns(physical_region_id, logical_region_id)
             .await?
             .into_iter()
             .map(|(_, column_metadata)| column_metadata)
             .collect::<Vec<_>>();
-
-        // sort columns on column id to ensure the order
+        // Sort columns on column name to ensure the order
         logical_column_metadata
             .sort_unstable_by(|c1, c2| c1.column_schema.name.cmp(&c2.column_schema.name));
+        // Update cache
+        self.state
+            .write()
+            .unwrap()
+            .add_logical_columns(logical_region_id, logical_column_metadata.clone());
 
         Ok(logical_column_metadata)
     }
+
+    /// Load logical column names of a logical region.
+    ///
+    /// The return value is ordered on column name alphabetically.
+    pub async fn load_logical_column_names(
+        &self,
+        physical_region_id: RegionId,
+        logical_region_id: RegionId,
+    ) -> Result<Vec<String>> {
+        // First try to load from state cache
+        if let Some(columns) = self
+            .state
+            .read()
+            .unwrap()
+            .logical_columns()
+            .get(&logical_region_id)
+        {
+            return Ok(columns
+                .iter()
+                .map(|c| c.column_schema.name.clone())
+                .collect());
+        }
+
+        // Else load from metadata region
+        let columns = self
+            .load_logical_columns(physical_region_id, logical_region_id)
+            .await?
+            .into_iter()
+            .map(|c| c.column_schema.name)
+            .collect::<Vec<_>>();
+
+        Ok(columns)
+    }
 }

src/metric-engine/src/engine/state.rs

@@ -17,6 +17,7 @@
 use std::collections::{HashMap, HashSet};
 
 use snafu::OptionExt;
+use store_api::metadata::ColumnMetadata;
 use store_api::storage::RegionId;
 
 use crate::error::{PhysicalRegionNotFoundSnafu, Result};
@@ -35,6 +36,10 @@ pub(crate) struct MetricEngineState {
     /// Cache for the columns of physical regions.
     /// The region id in key is the data region id.
     physical_columns: HashMap<RegionId, HashSet<String>>,
+    /// Cache for the column metadata of logical regions.
+    /// The column order is the same with the order in the metadata, which is
+    /// alphabetically ordered on column name.
+    logical_columns: HashMap<RegionId, Vec<ColumnMetadata>>,
 }
 
 impl MetricEngineState {
@@ -80,6 +85,21 @@ impl MetricEngineState {
             .insert(logical_region_id, physical_region_id);
     }
 
+    /// Add and reorder logical columns.
+    ///
+    /// Caller should make sure:
+    /// 1. there is no duplicate columns
+    /// 2. the column order is the same with the order in the metadata, which is
+    ///    alphabetically ordered on column name.
+    pub fn add_logical_columns(
+        &mut self,
+        logical_region_id: RegionId,
+        new_columns: impl IntoIterator<Item = ColumnMetadata>,
+    ) {
+        let columns = self.logical_columns.entry(logical_region_id).or_default();
+        columns.extend(new_columns);
+    }
+
     pub fn get_physical_region_id(&self, logical_region_id: RegionId) -> Option<RegionId> {
         self.logical_regions.get(&logical_region_id).copied()
     }
@@ -88,6 +108,10 @@ impl MetricEngineState {
         &self.physical_columns
     }
 
+    pub fn logical_columns(&self) -> &HashMap<RegionId, Vec<ColumnMetadata>> {
+        &self.logical_columns
+    }
+
     pub fn physical_regions(&self) -> &HashMap<RegionId, HashSet<RegionId>> {
         &self.physical_regions
     }
@@ -129,9 +153,15 @@ impl MetricEngineState {
             .unwrap() // Safety: physical_region_id is got from physical_regions
             .remove(&logical_region_id);
 
+        self.logical_columns.remove(&logical_region_id);
+
         Ok(())
     }
 
+    pub fn invalid_logical_column_cache(&mut self, logical_region_id: RegionId) {
+        self.logical_columns.remove(&logical_region_id);
+    }
+
     pub fn is_logical_region_exist(&self, logical_region_id: RegionId) -> bool {
         self.logical_regions().contains_key(&logical_region_id)
     }