feat: add region_statistics table (#4771)

* refactor: introduce `region_statistic`

* refactor: move DatanodeStat related structs to common_meta

* chore: add comments

* feat: implement `list_region_stats` for `ClusterInfo` trait

* feat: add `region_statistics` table

* feat: add table_id and region_number fields

* chore: rename unused snafu

* chore: udpate sqlness results

* chore: avoid to print source in error msg

* chore: move `procedure_info` under `greptime` catalog

* chore: apply suggestions from CR

* Update src/common/meta/src/datanode.rs

Co-authored-by: jeremyhi <jiachun_feng@proton.me>

---------

Co-authored-by: jeremyhi <jiachun_feng@proton.me>

src/store-api/src/region_engine.rs

@@ -242,6 +242,42 @@ pub type RegionScannerRef = Box<dyn RegionScanner>;
 
 pub type BatchResponses = Vec<(RegionId, Result<RegionResponse, BoxedError>)>;
 
+/// Represents the statistics of a region.
+#[derive(Debug, Deserialize, Serialize, Default)]
+pub struct RegionStatistic {
+    /// The size of memtable in bytes.
+    pub memtable_size: u64,
+    /// The size of WAL in bytes.
+    pub wal_size: u64,
+    /// The size of manifest in bytes.
+    pub manifest_size: u64,
+    /// The size of SST files in bytes.
+    pub sst_size: u64,
+}
+
+impl RegionStatistic {
+    /// Deserializes the region statistic to a byte array.
+    ///
+    /// Returns None if the deserialization fails.
+    pub fn deserialize_from_slice(value: &[u8]) -> Option<RegionStatistic> {
+        serde_json::from_slice(value).ok()
+    }
+
+    /// Serializes the region statistic to a byte array.
+    ///
+    /// Returns None if the serialization fails.
+    pub fn serialize_to_vec(&self) -> Option<Vec<u8>> {
+        serde_json::to_vec(self).ok()
+    }
+}
+
+impl RegionStatistic {
+    /// Returns the estimated disk size of the region.
+    pub fn estimated_disk_size(&self) -> u64 {
+        self.wal_size + self.sst_size + self.manifest_size
+    }
+}
+
 #[async_trait]
 pub trait RegionEngine: Send + Sync {
     /// Name of this engine
@@ -289,8 +325,8 @@ pub trait RegionEngine: Send + Sync {
     /// Retrieves region's metadata.
     async fn get_metadata(&self, region_id: RegionId) -> Result<RegionMetadataRef, BoxedError>;
 
-    /// Retrieves region's disk usage.
-    fn region_disk_usage(&self, region_id: RegionId) -> Option<i64>;
+    /// Retrieves region's statistic.
+    fn region_statistic(&self, region_id: RegionId) -> Option<RegionStatistic>;
 
     /// Stops the engine
     async fn stop(&self) -> Result<(), BoxedError>;