Implement sqlite3_db_status interface

ext/sqlite3/database.c

@@ -723,6 +723,24 @@ transaction_active_p(VALUE self)
     return sqlite3_get_autocommit(ctx->db) ? Qfalse : Qtrue;
 }
 
+/* call-seq: db.cache_misses
+ *
+ * Return the number of pager cache misses that have occurred.
+ *
+ */
+static VALUE
+cache_misses(VALUE self)
+{
+    sqlite3RubyPtr ctx;
+    TypedData_Get_Struct(self, sqlite3Ruby, &database_type, ctx);
+    REQUIRE_OPEN_DB(ctx);
+    int iCur, iHi;
+
+    sqlite3_db_status(ctx->db, SQLITE_DBSTATUS_CACHE_MISS, &iCur, &iHi, 0);
+
+    return INT2NUM(iCur);
+}
+
 static int
 hash_callback_function(VALUE callback_ary, int count, char **data, char **columns)
 {
@@ -877,6 +895,7 @@ init_sqlite3_database(void)
     rb_define_method(cSqlite3Database, "busy_timeout=", set_busy_timeout, 1);
     rb_define_method(cSqlite3Database, "extended_result_codes=", set_extended_result_codes, 1);
     rb_define_method(cSqlite3Database, "transaction_active?", transaction_active_p, 0);
+    rb_define_method(cSqlite3Database, "cache_misses", cache_misses, 0);
     rb_define_private_method(cSqlite3Database, "exec_batch", exec_batch, 2);
     rb_define_private_method(cSqlite3Database, "db_filename", db_filename, 1);
 

test/test_database.rb

@@ -651,5 +651,20 @@ def test_default_transaction_mode
     ensure
       tf&.unlink
     end
+
+    def test_cache_misses
+      db = SQLite3::Database.new('test.db')
+      db.execute("PRAGMA cache_size = -1;")
+      db.execute "CREATE TABLE example_table (id INTEGER PRIMARY KEY, data TEXT);"
+      10.times do |i|
+        db.execute 'INSERT INTO example_table (data) SELECT randomblob(1000);'
+      end
+      db.execute("SELECT * FROM example_table WHERE id BETWEEN 5000 AND 6000;")
+
+      assert_equal 28, db.cache_misses
+    ensure
+      db.close if db
+      File.delete( "test.db" )
+    end
   end
 end