Don't cache the database encoding

Database encoding can be changed, and we don't want to intercept all
queries just to check if someone changed the encoding. This commit
removes the encoding cache. If applications find that they are querying
the database encoding frequently, they should cache the return value of
this method themselves

Author: tenderlove

lib/sqlite3/database.rb

@@ -117,7 +117,6 @@ def initialize file, options = {}, zvfs = nil
 
       @tracefunc = nil
       @authorizer = nil
-      @encoding = nil
       @busy_handler = nil
       @collations = {}
       @functions = {}
@@ -138,9 +137,7 @@ def initialize file, options = {}, zvfs = nil
     #
     # Fetch the encoding set on this database
     def encoding
-      @encoding ||= prepare("PRAGMA encoding") { |stmt|
-        Encoding.find(stmt.first.first)
-      }
+      prepare("PRAGMA encoding") { |stmt| Encoding.find(stmt.first.first) }
     end
 
     # Installs (or removes) a block that will be invoked for every access

test/test_encoding.rb

@@ -13,6 +13,14 @@ def teardown
       @db.close
     end
 
+    def test_change_encoding
+      db = SQLite3::Database.new(":memory:")
+      assert_equal Encoding.find("UTF-8"), db.encoding
+
+      db.execute "PRAGMA encoding='UTF-16le'"
+      assert_equal Encoding.find("UTF-16le"), db.encoding
+    end
+
     def test_encoding_when_results_are_hash
       db = SQLite3::Database.new(":memory:", results_as_hash: true)
       assert_equal Encoding.find("UTF-8"), db.encoding