简单数据库实现——Part4 - 初次测试

简单数据库实现——Part4 - 初次测试

我们现在已经能够插入行和打印所有行了，让我们花点时间来测试一下我们得到了什么。

我将使用rspec来编写我的测试，因为我对它很熟悉（我不熟。。。），而且它的语法相当容易读。

这里提一下rspec安装
基本上按照官网来就行了，先要安装一个bundler。

sudo apt install bundler

然后创建一个文件Gemfile

vim Gemfile

在Gemfile中写入：

// 注意此处替换为国内源
source "https://gems.ruby-china.com"
gem 'rspec', '~> 3.0'

安装rspec+初始化

bundle install --binstubs
bin/rspec --init

我将定义一个helper来向数据库程序发送命令，然后对输出进行断言(assertion)处理。
在/spec目录下添加测试文件

describe 'database' do
  def run_script(commands)
    raw_output = nil
    IO.popen("./db", "r+") do |pipe|
      commands.each do |command|
        pipe.puts command
      end

      pipe.close_write

      # Read entire output
      raw_output = pipe.gets(nil)
    end
    raw_output.split("\n")
  end

  // 大概功能是执行一系列语句
  it 'inserts and retrieves a row' do
    result = run_script([
      "insert 1 user1 [email protected]",
      "select",
      ".exit",
    ])
    expect(result).to match_array([
      "db > Executed.",
      "db > (1, user1, [email protected])",
      "Executed.",
      "db > ",
    ])
  end
end

这个简单的测试可以确保我们得到我们输入的东西。
在根目录下进行测试：

bundle exec rspec
.

Finished in 0.00871 seconds (files took 0.09506 seconds to load)
1 example, 0 failures

接下来测试向数据库插入大量行。

it 'prints error message when table is full' do
  script = (1..1401).map do |i|
    "insert #{i} user#{i} person#{i}@example.com"
  end
  script << ".exit"
  result = run_script(script)
  expect(result[-2]).to eq('db > Error: Table full.')
end

测试结果，这个我一直有问题，最后写了个C测试了一下。正常测试结果如下：

bundle exec rspec
..

Finished in 0.01553 seconds (files took 0.08156 seconds to load)
2 examples, 0 failures

我们的数据库现在可以容纳1400行，因为我们将页面的最大数量设置为100，一个页面可以容纳14行。应次测试的是1401行。

这个测试实在是不会用，后面我都是手动测试的。他测试完后发现一个问题，支持的用户名和电子邮件长度最长时会出现问题，原因是字符串结尾的空字符，解决方法是将长度+1。如下：

 const uint32_t COLUMN_EMAIL_SIZE = 255;
 typedef struct {
   uint32_t id;
-  char username[COLUMN_USERNAME_SIZE];
-  char email[COLUMN_EMAIL_SIZE];
+  char username[COLUMN_USERNAME_SIZE + 1];
+  char email[COLUMN_EMAIL_SIZE + 1];
 } Row;

我们不应该允许插入用户名或电子邮件的长度超过列的大小。为了做到这一点，我们需要升级我们的解析器。不再使用scanf()，而使用strtok()。

+PrepareResult prepare_insert(InputBuffer* input_buffer, Statement* statement) {
+  statement->type = STATEMENT_INSERT;
+
+  char* keyword = strtok(input_buffer->buffer, " ");
+  char* id_string = strtok(NULL, " ");
+  char* username = strtok(NULL, " ");
+  char* email = strtok(NULL, " ");
+
+  if (id_string == NULL || username == NULL || email == NULL) {
+    return PREPARE_SYNTAX_ERROR;
+  }
+
+  int id = atoi(id_string);
+  if (strlen(username) > COLUMN_USERNAME_SIZE) {
+    return PREPARE_STRING_TOO_LONG;
+  }
+  if (strlen(email) > COLUMN_EMAIL_SIZE) {
+    return PREPARE_STRING_TOO_LONG;
+  }
+
+  statement->row_to_insert.id = id;
+  strcpy(statement->row_to_insert.username, username);
+  strcpy(statement->row_to_insert.email, email);
+
+  return PREPARE_SUCCESS;
+}
+
 PrepareResult prepare_statement(InputBuffer* input_buffer,
                                 Statement* statement) {
   if (strncmp(input_buffer->buffer, "insert", 6) == 0) {
+    return prepare_insert(input_buffer, statement);
-    statement->type = STATEMENT_INSERT;
-    int args_assigned = sscanf(
-        input_buffer->buffer, "insert %d %s %s", &(statement->row_to_insert.id),
-        statement->row_to_insert.username, statement->row_to_insert.email);
-    if (args_assigned < 3) {
-      return PREPARE_SYNTAX_ERROR;
-    }
-    return PREPARE_SUCCESS;
   }

我们可以对每个文本值调用strlen()来查看它是否太长。
我们可以像处理其他错误代码一样处理错误

 enum PrepareResult_t {
   PREPARE_SUCCESS,
+  PREPARE_STRING_TOO_LONG,
   PREPARE_SYNTAX_ERROR,
   PREPARE_UNRECOGNIZED_STATEMENT
 };

 switch (prepare_statement(input_buffer, &statement)) {
   case (PREPARE_SUCCESS):
     break;
+  case (PREPARE_STRING_TOO_LONG):
+    printf("String is too long.\n");
+    continue;
   case (PREPARE_SYNTAX_ERROR):
     printf("Syntax error. Could not parse statement.\n");
     continue;

我们不妨再处理一个错误情况——ID为负。

 enum PrepareResult_t {
   PREPARE_SUCCESS,
+  PREPARE_NEGATIVE_ID,
   PREPARE_STRING_TOO_LONG,
   PREPARE_SYNTAX_ERROR,
   PREPARE_UNRECOGNIZED_STATEMENT
@@ -148,9 +147,6 @@ PrepareResult prepare_insert(InputBuffer* input_buffer, Statement* statement) {
   }

   int id = atoi(id_string);
+  if (id < 0) {
+    return PREPARE_NEGATIVE_ID;
+  }
   if (strlen(username) > COLUMN_USERNAME_SIZE) {
     return PREPARE_STRING_TOO_LONG;
   }
@@ -230,9 +226,6 @@ int main(int argc, char* argv[]) {
     switch (prepare_statement(input_buffer, &statement)) {
       case (PREPARE_SUCCESS):
         break;
+      case (PREPARE_NEGATIVE_ID):
+        printf("ID must be positive.\n");
+        continue;
       case (PREPARE_STRING_TOO_LONG):
         printf("String is too long.\n");
         continue;

测试到此为止，接下来是一个非常重要的功能：持久性！我们将数据库保存到文件中，然后再次读出。

修改的部分

@@ -22,6 +22,8 @@

 enum PrepareResult_t {
   PREPARE_SUCCESS,
+  PREPARE_NEGATIVE_ID,
+  PREPARE_STRING_TOO_LONG,
   PREPARE_SYNTAX_ERROR,
   PREPARE_UNRECOGNIZED_STATEMENT
  };
@@ -34,8 +36,8 @@
 #define COLUMN_EMAIL_SIZE 255
 typedef struct {
   uint32_t id;
-  char username[COLUMN_USERNAME_SIZE];
-  char email[COLUMN_EMAIL_SIZE];
+  char username[COLUMN_USERNAME_SIZE + 1];
+  char email[COLUMN_EMAIL_SIZE + 1];
 } Row;

@@ -150,18 +152,40 @@ MetaCommandResult do_meta_command(InputBuffer* input_buffer, Table *table) {
   }
 }

-PrepareResult prepare_statement(InputBuffer* input_buffer,
-                                Statement* statement) {
-  if (strncmp(input_buffer->buffer, "insert", 6) == 0) {
+PrepareResult prepare_insert(InputBuffer* input_buffer, Statement* statement) {
   statement->type = STATEMENT_INSERT;
-  int args_assigned = sscanf(
-     input_buffer->buffer, "insert %d %s %s", &(statement->row_to_insert.id),
-     statement->row_to_insert.username, statement->row_to_insert.email
-     );
-  if (args_assigned < 3) {
+
+  char* keyword = strtok(input_buffer->buffer, " ");
+  char* id_string = strtok(NULL, " ");
+  char* username = strtok(NULL, " ");
+  char* email = strtok(NULL, " ");
+
+  if (id_string == NULL || username == NULL || email == NULL) {
      return PREPARE_SYNTAX_ERROR;
   }
+
+  int id = atoi(id_string);
+  if (id < 0) {
+     return PREPARE_NEGATIVE_ID;
+  }
+  if (strlen(username) > COLUMN_USERNAME_SIZE) {
+     return PREPARE_STRING_TOO_LONG;
+  }
+  if (strlen(email) > COLUMN_EMAIL_SIZE) {
+     return PREPARE_STRING_TOO_LONG;
+  }
+
+  statement->row_to_insert.id = id;
+  strcpy(statement->row_to_insert.username, username);
+  strcpy(statement->row_to_insert.email, email);
+
   return PREPARE_SUCCESS;
+
+}
+PrepareResult prepare_statement(InputBuffer* input_buffer,
+                                Statement* statement) {
+  if (strncmp(input_buffer->buffer, "insert", 6) == 0) {
+      return prepare_insert(input_buffer, statement);
   }
   if (strcmp(input_buffer->buffer, "select") == 0) {
     statement->type = STATEMENT_SELECT;
@@ -223,6 +247,12 @@ int main(int argc, char* argv[]) {
     switch (prepare_statement(input_buffer, &statement)) {
       case (PREPARE_SUCCESS):
         break;
+      case (PREPARE_NEGATIVE_ID):
+	printf("ID must be positive.\n");
+	continue;
+      case (PREPARE_STRING_TOO_LONG):
+	printf("String is too long.\n");
+	continue;
       case (PREPARE_SYNTAX_ERROR):
 	printf("Syntax error. Could not parse statement.\n");
 	continue;