From 811f019e471f7fc08ce8fa7b341f0040fbe9a570 Mon Sep 17 00:00:00 2001
From: shee <13843187+qzsee@users.noreply.github.com>
Date: Fri, 6 May 2022 17:43:14 -0700
Subject: [PATCH] [performance][query]improve the performance of DISTINCT
 aggregation by using flat hash set replace unordered set (#9401)

Co-authored-by: shizhiqiang03 <shizhiqiang03@meituan.com>
---
 be/src/exprs/aggregate_functions.cpp | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/be/src/exprs/aggregate_functions.cpp b/be/src/exprs/aggregate_functions.cpp
index 590e07838a..257aca4a38 100644
--- a/be/src/exprs/aggregate_functions.cpp
+++ b/be/src/exprs/aggregate_functions.cpp
@@ -1346,7 +1346,8 @@ private:
         }
     };
 
-    std::unordered_set<T, NumericHashHelper> _set;
+    phmap::flat_hash_set<T, NumericHashHelper> _set;
+
     // Because Anyval does not provide the hash function, in order
     // to adopt the type different from the template, the pointer is used
     // HybridSetBase* _set;
@@ -1503,7 +1504,8 @@ public:
 private:
     const int DECIMAL_BYTE_SIZE = 16;
 
-    std::unordered_set<DecimalV2Value> _set;
+    phmap::flat_hash_set<DecimalV2Value> _set;
+
     FunctionContext::Type _type;
 };
 
@@ -1588,7 +1590,8 @@ private:
     const int DATETIME_PACKED_TIME_BYTE_SIZE = 8;
     const int DATETIME_TYPE_BYTE_SIZE = 4;
 
-    std::unordered_set<DateTimeVal, DateTimeHashHelper> _set;
+    phmap::flat_hash_set<DateTimeVal, DateTimeHashHelper> _set;
+
     FunctionContext::Type _type;
 };