From 9e1208a79389172ee95523a02722d0791860589a Mon Sep 17 00:00:00 2001
From: HarryLeeIBM <hleeatwork@outlook.com>
Date: Mon, 2 Oct 2023 15:20:35 -0700
Subject: [PATCH] Speed up inverted index building using flat_hash_map

---
 src/Common/FST.h                       | 6 +++---
 src/Storages/MergeTree/GinIndexStore.h | 3 ++-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/Common/FST.h b/src/Common/FST.h
index 64c3c8853f6..7e51b807303 100644
--- a/src/Common/FST.h
+++ b/src/Common/FST.h
@@ -3,13 +3,13 @@
 #include <map>
 #include <memory>
 #include <string>
-#include <unordered_map>
 #include <unordered_set>
 #include <vector>
 #include <Core/Types.h>
 #include <IO/ReadHelpers.h>
 #include <IO/WriteBuffer.h>
 #include <base/types.h>
+#include <absl/container/flat_hash_map.h>
 
 namespace DB
 {
@@ -107,7 +107,7 @@ public:
     UInt64 state_index = 0;
 
     /// Arcs which are started from state, the 'char' is the label on the arc
-    std::unordered_map<char, Arc> arcs;
+    absl::flat_hash_map<char, Arc> arcs;
 
 private:
     struct FlagValues
@@ -146,7 +146,7 @@ private:
     StatePtr initial_state;
 
     /// map of (state_hash, StatePtr)
-    std::unordered_map<UInt64, StatePtr> minimized_states;
+    absl::flat_hash_map<UInt64, StatePtr> minimized_states;
 
     /// Next available ID of state
     UInt64 next_id = 1;
diff --git a/src/Storages/MergeTree/GinIndexStore.h b/src/Storages/MergeTree/GinIndexStore.h
index cf6ce2e8625..b86de546ecb 100644
--- a/src/Storages/MergeTree/GinIndexStore.h
+++ b/src/Storages/MergeTree/GinIndexStore.h
@@ -11,6 +11,7 @@
 #include <mutex>
 #include <unordered_map>
 #include <vector>
+#include <absl/container/flat_hash_map.h>
 
 /// GinIndexStore manages the generalized inverted index ("gin") for a data part, and it is made up of one or more immutable
 /// index segments.
@@ -124,7 +125,7 @@ class GinIndexStore
 {
 public:
     /// Container for all term's Gin Index Postings List Builder
-    using GinIndexPostingsBuilderContainer = std::unordered_map<std::string, GinIndexPostingsBuilderPtr>;
+    using GinIndexPostingsBuilderContainer = absl::flat_hash_map<std::string, GinIndexPostingsBuilderPtr>;
 
     GinIndexStore(const String & name_, DataPartStoragePtr storage_);
     GinIndexStore(const String & name_, DataPartStoragePtr storage_, MutableDataPartStoragePtr data_part_storage_builder_, UInt64 max_digestion_size_);