From 2f36c9e965b01ca68a795499bfbdbec020c47609 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@clickhouse.com>
Date: Fri, 16 Feb 2024 00:56:24 +0100
Subject: [PATCH 1/2] Maybe less memory usage for primary keys in memory

---
 src/Storages/MergeTree/IMergeTreeDataPart.cpp | 1 +
 src/Storages/MergeTree/IMergeTreeDataPart.h   | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Storages/MergeTree/IMergeTreeDataPart.cpp b/src/Storages/MergeTree/IMergeTreeDataPart.cpp
index 0f82e00edff3..9e264cba3f86 100644
--- a/src/Storages/MergeTree/IMergeTreeDataPart.cpp
+++ b/src/Storages/MergeTree/IMergeTreeDataPart.cpp
@@ -842,6 +842,7 @@ void IMergeTreeDataPart::loadIndex()
 
         for (size_t i = 0; i < key_size; ++i)
         {
+            loaded_index[i]->shrinkToFit();
             loaded_index[i]->protect();
             if (loaded_index[i]->size() != marks_count)
                 throw Exception(ErrorCodes::CANNOT_READ_ALL_DATA, "Cannot read all data from index file {}(expected size: "
diff --git a/src/Storages/MergeTree/IMergeTreeDataPart.h b/src/Storages/MergeTree/IMergeTreeDataPart.h
index fcf9d5bd17da..8da9298b2908 100644
--- a/src/Storages/MergeTree/IMergeTreeDataPart.h
+++ b/src/Storages/MergeTree/IMergeTreeDataPart.h
@@ -660,7 +660,7 @@ class IMergeTreeDataPart : public std::enable_shared_from_this<IMergeTreeDataPar
 
     virtual void appendFilesOfIndexGranularity(Strings & files) const;
 
-    /// Loads index file.
+    /// Loads the index file.
     void loadIndex();
 
     void appendFilesOfIndex(Strings & files) const;

From 20b9e519ffd30108e66a4457240a59696bca0181 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@clickhouse.com>
Date: Sat, 17 Feb 2024 04:59:32 +0100
Subject: [PATCH 2/2] Add a test

---
 .../1_stateful/00098_primary_key_memory_allocated.reference      | 1 +
 tests/queries/1_stateful/00098_primary_key_memory_allocated.sql  | 1 +
 2 files changed, 2 insertions(+)
 create mode 100644 tests/queries/1_stateful/00098_primary_key_memory_allocated.reference
 create mode 100644 tests/queries/1_stateful/00098_primary_key_memory_allocated.sql

diff --git a/tests/queries/1_stateful/00098_primary_key_memory_allocated.reference b/tests/queries/1_stateful/00098_primary_key_memory_allocated.reference
new file mode 100644
index 000000000000..72749c905a31
--- /dev/null
+++ b/tests/queries/1_stateful/00098_primary_key_memory_allocated.reference
@@ -0,0 +1 @@
+1	1	1
diff --git a/tests/queries/1_stateful/00098_primary_key_memory_allocated.sql b/tests/queries/1_stateful/00098_primary_key_memory_allocated.sql
new file mode 100644
index 000000000000..7371678a0f6f
--- /dev/null
+++ b/tests/queries/1_stateful/00098_primary_key_memory_allocated.sql
@@ -0,0 +1 @@
+SELECT primary_key_bytes_in_memory < 16000, primary_key_bytes_in_memory_allocated < 16000, primary_key_bytes_in_memory_allocated / primary_key_bytes_in_memory < 1.1 FROM system.parts WHERE database = 'test' AND table = 'hits';