From 6f26e99cef4b6f20be8ef5cf7fee4b4755baaaec Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Fri, 5 Apr 2019 14:45:05 +0200
Subject: Improve == and hash methods on various schema cache structs to be
 allocation free.

The previous implementation would allocate 2 arrays per comparisons.

I tried relying on Struct, but they do allocate one Hash inside `Struct#hash`.
---
 .../lib/active_record/connection_adapters/column.rb | 21 +++++++++++++--------
 .../connection_adapters/mysql/type_metadata.rb      | 13 +++++--------
 .../connection_adapters/postgresql/type_metadata.rb | 17 +++++++++--------
 .../connection_adapters/sql_type_metadata.rb        | 19 +++++++++++--------
 4 files changed, 38 insertions(+), 32 deletions(-)

(limited to 'activerecord')

diff --git a/activerecord/lib/active_record/connection_adapters/column.rb b/activerecord/lib/active_record/connection_adapters/column.rb
index 8c294ccf5a..21c5e43ea0 100644
--- a/activerecord/lib/active_record/connection_adapters/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/column.rb
@@ -63,19 +63,24 @@ module ActiveRecord
 
       def ==(other)
         other.is_a?(Column) &&
-          attributes_for_hash == other.attributes_for_hash
+          name == other.name &&
+          default == other.default &&
+          sql_type_metadata == other.sql_type_metadata &&
+          null == other.null &&
+          default_function == other.default_function &&
+          collation == other.collation
       end
       alias :eql? :==
 
       def hash
-        attributes_for_hash.hash
+        Column.hash ^
+          name.hash ^
+          default.hash ^
+          sql_type_metadata.hash ^
+          null.hash ^
+          default_function.hash ^
+          collation.hash
       end
-
-      protected
-
-        def attributes_for_hash
-          [self.class, name, default, sql_type_metadata, null, default_function, collation, comment]
-        end
     end
 
     class NullColumn < Column
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb b/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb
index 7ad0944d51..56479f27bf 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb
@@ -16,19 +16,16 @@ module ActiveRecord
 
         def ==(other)
           other.is_a?(MySQL::TypeMetadata) &&
-            attributes_for_hash == other.attributes_for_hash
+            __getobj__ == other.__getobj__ &&
+            extra == other.extra
         end
         alias eql? ==
 
         def hash
-          attributes_for_hash.hash
+          TypeMetadata.hash ^
+            __getobj__.hash ^
+            extra.hash
         end
-
-        protected
-
-          def attributes_for_hash
-            [self.class, @type_metadata, extra]
-          end
       end
     end
   end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb b/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
index cd69d28139..403b3ead98 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
@@ -22,19 +22,20 @@ module ActiveRecord
 
       def ==(other)
         other.is_a?(PostgreSQLTypeMetadata) &&
-          attributes_for_hash == other.attributes_for_hash
+          __getobj__ == other.__getobj__ &&
+          oid == other.oid &&
+          fmod == other.fmod &&
+          array == other.array
       end
       alias eql? ==
 
       def hash
-        attributes_for_hash.hash
+        PostgreSQLTypeMetadata.hash ^
+          __getobj__.hash ^
+          oid.hash ^
+          fmod.hash ^
+          array.hash
       end
-
-      protected
-
-        def attributes_for_hash
-          [self.class, @type_metadata, oid, fmod]
-        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb b/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb
index 8489bcbf1d..df28df7a7c 100644
--- a/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb
+++ b/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb
@@ -16,19 +16,22 @@ module ActiveRecord
 
       def ==(other)
         other.is_a?(SqlTypeMetadata) &&
-          attributes_for_hash == other.attributes_for_hash
+          sql_type == other.sql_type &&
+          type == other.type &&
+          limit == other.limit &&
+          precision == other.precision &&
+          scale == other.scale
       end
       alias eql? ==
 
       def hash
-        attributes_for_hash.hash
+        SqlTypeMetadata.hash ^
+          sql_type.hash ^
+          type.hash ^
+          limit.hash ^
+          precision.hash >> 1 ^
+          scale.hash >> 2
       end
-
-      protected
-
-        def attributes_for_hash
-          [self.class, sql_type, type, limit, precision, scale]
-        end
     end
   end
 end
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