From a9f3c4b17c4a1c52a76b451e727dc9f317351f90 Mon Sep 17 00:00:00 2001
From: evenyag <realevenyag@gmail.com>
Date: Mon, 4 Nov 2024 20:08:56 +0800
Subject: [PATCH] chore: page reader metrics

---
 src/mito2/src/metrics.rs               | 1 +
 src/mito2/src/sst/parquet/row_group.rs | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/mito2/src/metrics.rs b/src/mito2/src/metrics.rs
index c50bbbdc78..62a6fe8012 100644
--- a/src/mito2/src/metrics.rs
+++ b/src/mito2/src/metrics.rs
@@ -134,6 +134,7 @@ lazy_static! {
     )
     .unwrap();
     pub static ref READ_STAGE_FETCH_PAGES: Histogram = READ_STAGE_ELAPSED.with_label_values(&["fetch_pages"]);
+    pub static ref READ_STAGE_BUILD_PAGE_READER: Histogram = READ_STAGE_ELAPSED.with_label_values(&["build_page_reader"]);
     /// Counter of rows read from different source.
     pub static ref READ_ROWS_TOTAL: IntCounterVec =
         register_int_counter_vec!("greptime_mito_read_rows_total", "mito read rows total", &[TYPE_LABEL]).unwrap();
diff --git a/src/mito2/src/sst/parquet/row_group.rs b/src/mito2/src/sst/parquet/row_group.rs
index 73382c06d9..d0e95c5c1b 100644
--- a/src/mito2/src/sst/parquet/row_group.rs
+++ b/src/mito2/src/sst/parquet/row_group.rs
@@ -33,7 +33,7 @@ use tokio::task::yield_now;
 
 use crate::cache::file_cache::{FileType, IndexKey};
 use crate::cache::{CacheManagerRef, PageKey, PageValue};
-use crate::metrics::{READ_STAGE_ELAPSED, READ_STAGE_FETCH_PAGES};
+use crate::metrics::{READ_STAGE_BUILD_PAGE_READER, READ_STAGE_ELAPSED, READ_STAGE_FETCH_PAGES};
 use crate::sst::file::FileId;
 use crate::sst::parquet::helper::fetch_byte_ranges;
 use crate::sst::parquet::page_reader::RowGroupCachedReader;
@@ -308,6 +308,7 @@ impl<'a> InMemoryRowGroup<'a> {
 
     /// Creates a page reader to read column at `i`.
     fn column_page_reader(&self, i: usize) -> Result<Box<dyn PageReader>> {
+        let _timer = READ_STAGE_BUILD_PAGE_READER.start_timer();
         if let Some(cached_pages) = &self.column_uncompressed_pages[i] {
             debug_assert!(!cached_pages.row_group.is_empty());
             // Hits the row group level page cache.