feat: Add first/last write time on DbChunk

To eventually be used in collect_rub

server/src/db/chunk.rs

@@ -1,6 +1,7 @@
 use super::{
     catalog::chunk::ChunkMetadata, pred::to_read_buffer_predicate, streams::ReadFilterResultsStream,
 };
+use chrono::{DateTime, Utc};
 use data_types::partition_metadata;
 use datafusion::physical_plan::SendableRecordBatchStream;
 use datafusion_util::MemoryStream;
@@ -201,6 +202,20 @@ impl DbChunk {
     pub fn table_name(&self) -> Arc<str> {
         Arc::clone(&self.table_name)
     }
+
+    pub fn time_of_first_write(&self) -> DateTime<Utc> {
+        match &self.state {
+            State::MutableBuffer { chunk } => chunk.table_summary().time_of_first_write,
+            _ => unimplemented!(),
+        }
+    }
+
+    pub fn time_of_last_write(&self) -> DateTime<Utc> {
+        match &self.state {
+            State::MutableBuffer { chunk } => chunk.table_summary().time_of_last_write,
+            _ => unimplemented!(),
+        }
+    }
 }
 
 impl QueryChunk for DbChunk {