Use result.rows as fastest alternative

Author: kamipo

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -505,12 +505,12 @@ def table_structure_with_collation(table_name, basic_structure)
           # Result will have following sample string
           # CREATE TABLE "users" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
           #                       "password_digest" varchar COLLATE "NOCASE");
-          result = exec_query(sql, "SCHEMA").first
+          result = query_value(sql, "SCHEMA")
 
           if result
             # Splitting with left parentheses and discarding the first part will return all
             # columns separated with comma(,).
-            columns_string = result["sql"].split("(", 2).last
+            columns_string = result.split("(", 2).last
 
             columns_string.split(",").each do |column_string|
               # This regex will match the column name and collation type and will save

activerecord/lib/active_record/relation.rb

@@ -367,14 +367,12 @@ def compute_cache_version(timestamp_column) # :nodoc:
           arel = query.arel
         end
 
-        result = connection.select_one(arel, nil)
+        size, timestamp = connection.select_rows(arel, nil).first
 
-        if result
+        if size
           column_type = klass.type_for_attribute(timestamp_column)
-          timestamp = column_type.deserialize(result["timestamp"])
-          size = result["size"]
+          timestamp = column_type.deserialize(timestamp)
         else
-          timestamp = nil
           size = 0
         end
       end

activerecord/lib/active_record/relation/finder_methods.rb

@@ -316,7 +316,7 @@ def exists?(conditions = :none)
 
       relation = construct_relation_for_exists(conditions)
 
-      skip_query_cache_if_necessary { connection.select_one(relation.arel, "#{name} Exists?") } ? true : false
+      skip_query_cache_if_necessary { connection.select_rows(relation.arel, "#{name} Exists?").size == 1 }
     end
 
     # This method is called whenever no records are found with either a single
@@ -416,8 +416,8 @@ def limited_ids_for(relation)
 
         relation = relation.except(:select).select(values).distinct!
 
-        id_rows = skip_query_cache_if_necessary { @klass.connection.select_all(relation.arel, "SQL") }
-        id_rows.map { |row| row[primary_key] }
+        id_rows = skip_query_cache_if_necessary { @klass.connection.select_rows(relation.arel, "SQL") }
+        id_rows.map(&:last)
       end
 
       def using_limitable_reflections?(reflections)