resolve PR comments

src/mito2/src/metrics.rs

@@ -323,12 +323,4 @@ lazy_static! {
         "mito manifest operation elapsed",
         &["op"]
     ).unwrap();
-
-    // Parquet related metrics:
-
-    /// Elapsed time of loading parquet metadata.
-    pub static ref PARQUET_METADATA_LOAD_ELAPSED: Histogram = register_histogram!(
-        "greptime_parquet_metadata_load_elapsed",
-        "parquet metadata load elapsed",
-    ).unwrap();
 }

src/mito2/src/sst/parquet/metadata.rs

@@ -19,7 +19,6 @@ use parquet::file::FOOTER_SIZE;
 use snafu::ResultExt;
 
 use crate::error::{self, Result};
-use crate::metrics::PARQUET_METADATA_LOAD_ELAPSED;
 
 /// The estimated size of the footer and metadata need to read from the end of parquet file.
 const DEFAULT_PREFETCH_SIZE: u64 = 64 * 1024;
@@ -68,8 +67,6 @@ impl<'a> MetadataLoader<'a> {
     ///
     /// Refer to https://github.com/apache/arrow-rs/blob/093a10e46203be1a0e94ae117854701bf58d4c79/parquet/src/arrow/async_reader/metadata.rs#L55-L106
     pub async fn load(&self) -> Result<ParquetMetaData> {
-        let _t = PARQUET_METADATA_LOAD_ELAPSED.start_timer();
-
         let object_store = &self.object_store;
         let path = self.file_path;
         let file_size = self.get_file_size().await?;

src/mito2/src/sst/parquet/reader.rs

@@ -302,6 +302,10 @@ impl ParquetReaderBuilder {
         file_path: &str,
         file_size: u64,
     ) -> Result<Arc<ParquetMetaData>> {
+        let _t = READ_STAGE_ELAPSED
+            .with_label_values(&["read_parquet_metadata"])
+            .start_timer();
+
         let region_id = self.file_handle.region_id();
         let file_id = self.file_handle.file_id();
         // Tries to get from global cache.