From b731f598fc076acbcaeb273636e646dfebeef796 Mon Sep 17 00:00:00 2001
From: Ryuta Kamizono <kamipo@gmail.com>
Date: Sun, 28 May 2017 13:27:41 +0900
Subject: [PATCH] Prevent extra `current_database` query for
 `encoding`/`collation`/`ctype`

---
 .../postgresql/schema_statements.rb                  |  6 +++---
 .../cases/adapters/postgresql/connection_test.rb     | 12 +++++++++---
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index 5b483ad4ab..3eff9e2f83 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -186,17 +186,17 @@ module ActiveRecord
 
         # Returns the current database encoding format.
         def encoding
-          select_value("SELECT pg_encoding_to_char(encoding) FROM pg_database WHERE datname LIKE '#{current_database}'", "SCHEMA")
+          select_value("SELECT pg_encoding_to_char(encoding) FROM pg_database WHERE datname = current_database()", "SCHEMA")
         end
 
         # Returns the current database collation.
         def collation
-          select_value("SELECT datcollate FROM pg_database WHERE datname LIKE '#{current_database}'", "SCHEMA")
+          select_value("SELECT datcollate FROM pg_database WHERE datname = current_database()", "SCHEMA")
         end
 
         # Returns the current database ctype.
         def ctype
-          select_value("SELECT datctype FROM pg_database WHERE datname LIKE '#{current_database}'", "SCHEMA")
+          select_value("SELECT datctype FROM pg_database WHERE datname = current_database()", "SCHEMA")
         end
 
         # Returns an array of schema names.
diff --git a/activerecord/test/cases/adapters/postgresql/connection_test.rb b/activerecord/test/cases/adapters/postgresql/connection_test.rb
index 3deb007513..32afe331fa 100644
--- a/activerecord/test/cases/adapters/postgresql/connection_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/connection_test.rb
@@ -31,15 +31,21 @@ module ActiveRecord
     end
 
     def test_encoding
-      assert_not_nil @connection.encoding
+      assert_queries(1) do
+        assert_not_nil @connection.encoding
+      end
     end
 
     def test_collation
-      assert_not_nil @connection.collation
+      assert_queries(1) do
+        assert_not_nil @connection.collation
+      end
     end
 
     def test_ctype
-      assert_not_nil @connection.ctype
+      assert_queries(1) do
+        assert_not_nil @connection.ctype
+      end
     end
 
     def test_default_client_min_messages