From d8acb0e7ad1e86dcc350793a33b218143a228718 Mon Sep 17 00:00:00 2001
From: Igor Nikonov <igor@clickhouse.com>
Date: Tue, 13 Sep 2022 12:06:56 +0000
Subject: [PATCH] Tiny improvements along the code

- less allocations (potentially)
---
 src/Core/Block.cpp                 | 1 +
 src/Interpreters/TreeOptimizer.cpp | 6 +++---
 src/Storages/SelectQueryInfo.h     | 6 +++---
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/Core/Block.cpp b/src/Core/Block.cpp
index 3b7595eb886..33691e83d27 100644
--- a/src/Core/Block.cpp
+++ b/src/Core/Block.cpp
@@ -623,6 +623,7 @@ NamesAndTypesList Block::getNamesAndTypesList() const
 NamesAndTypes Block::getNamesAndTypes() const
 {
     NamesAndTypes res;
+    res.reserve(columns());
 
     for (const auto & elem : data)
         res.emplace_back(elem.name, elem.type);
diff --git a/src/Interpreters/TreeOptimizer.cpp b/src/Interpreters/TreeOptimizer.cpp
index 3f7e141db3e..74f084df40b 100644
--- a/src/Interpreters/TreeOptimizer.cpp
+++ b/src/Interpreters/TreeOptimizer.cpp
@@ -418,7 +418,7 @@ void optimizeDuplicateDistinct(ASTSelectQuery & select)
         return;
 
     std::unordered_set<String> distinct_names = getDistinctNames(*subselect);
-    std::unordered_set<String> selected_names;
+    std::unordered_set<std::string_view> selected_names;
 
     /// Check source column names from select list (ignore aliases and table names)
     for (const auto & id : select.select()->children)
@@ -427,11 +427,11 @@ void optimizeDuplicateDistinct(ASTSelectQuery & select)
         if (!identifier)
             return;
 
-        String name = identifier->shortName();
+        const String & name = identifier->shortName();
         if (!distinct_names.contains(name))
             return; /// Not a distinct column, keep DISTINCT for it.
 
-        selected_names.insert(name);
+        selected_names.emplace(name);
     }
 
     /// select columns list != distinct columns list
diff --git a/src/Storages/SelectQueryInfo.h b/src/Storages/SelectQueryInfo.h
index c41b422199d..f2835ab4dbf 100644
--- a/src/Storages/SelectQueryInfo.h
+++ b/src/Storages/SelectQueryInfo.h
@@ -117,10 +117,10 @@ struct InputOrderInfo
      * sort_description_for_merging will be equal to (c, d) and
      * used_prefix_of_sorting_key_size will be equal to 4.
      */
-    size_t used_prefix_of_sorting_key_size;
+    const size_t used_prefix_of_sorting_key_size;
 
-    int direction;
-    UInt64 limit;
+    const int direction;
+    const UInt64 limit;
 
     InputOrderInfo(
         const SortDescription & sort_description_for_merging_,