前文回顾
实现一个简单的Database1(译文)
实现一个简单的Database2(译文)
实现一个简单的Database3(译文)
译注:cstsck在github维护了一个简单的、类似SQLite的数据库实现,通过这个简单的项目,可以很好的理解数据库是如何运行的。本文是第四篇,主要是使用rspec对目前实现的功能进行测试并解决测试出现BUG
译注:cstsck在github维护了一个简单的、类似sqlite的数据库实现,通过这个简单的项目,可以很好的理解数据库是如何运行的。本文是第四篇,主要是使用rspec对目前实现的功能进行测试并解决测试出现BUG
Part 4 我们的第一个测试(和BUG)
我们已经获得插入数据到数据库并打印所有数据的能力。现在来测试一下目前microseconds已有的功能。
我要使用rspec来写我的测试,因为我对rspec很熟悉,它的语法也相当易读。
译注:rsepec 是一个基于Ruby的测试框架,语法非常简单,可以很方便的测试各种可执行程序,判断输出
我定义一个短小的help来发送一个帮助命令列表到数据库,然后对输出进行断言。
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
it \'inserts and retrieves a row\' do
result = run_script([
\"insert 1 user1 person1@example.com\",
\"select\",
\".exit\",
])
expect(result).to match_array([
\"db > Executed.\",
\"db > (1, user1, person1@example.com)\",
\"Executed.\",
\"db > \",
])
end
end
这个简单的测试是确认我们的输入能够获取返回结果。并确保能通过测试:
bundle exec rspec
.
Finished in 0.00871 seconds (files took 0.09506 seconds to load)
1 example, 0 failures
现在测试插入更多行数据到数据库是可行的:
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
再次运行测试:
bundle exec rspec
..
Finished in 0.01553 seconds (files took 0.08156 seconds to load)
2 examples, 0 failures
妙啊,测试通过了!我们的数据库现在能够hold住1400行数据,这是因为我们设置pages最大数量是100页,每页可以存放14行数据。
查看我们目前写的的代码,我意识到我们可能没有正确处理存储文本字段。很容易用下面的例子测试出来(插入边界长度的字符串):
it \'allows inserting strings that are the maximum length\' do
long_username = \"a\"*32
long_email = \"a\"*255
script = [
\"insert 1 #{long_username} #{long_email}\",
\"select\",
\".exit\",
]
result = run_script(script)
expect(result).to match_array([
\"db > Executed.\",
\"db > (1, #{long_username}, #{long_email})\",
\"Executed.\",
\"db > \",
])
end
测试失败了:
Failures:
1) database allows inserting strings that are the maximum length
Failure/Error: raw_output.split(\"\\n\")
ArgumentError:
invalid byte sequence in UTF-8
# ./spec/main_spec.rb:14:in `split\'
# ./spec/main_spec.rb:14:in `run_script\'
# ./spec/main_spec.rb:48:in `block (2 levels) in <top (required)>\'
如果是我们自己人工来测试,当我们打印行数据时,会看到有一些奇怪的字符(例子中,我把很长的字符串进行了缩写):
db > insert 1 aaaaa... aaaaa...
Executed.
db > select
(1, aaaaa...aaa\\�, aaaaa...aaa\\�)
Executed.
db >
发生了什么?如果看一下代码中我们定义的Row结构,我们确实为username字段分配了32个字节长度,为email字段分配255个字节长度。但是C语言的strings是以一个null字符来作为结尾的,这个字符我们没有为它分配空间。解决方法就是多分配一个额外的字节(来存放这个null字符):
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;
这样确实解决了上面的问题(重新运行上面插入边界长度字符串的测试):
bundle exec rspec
...
Finished in 0.0188 seconds (files took 0.08516 seconds to load)
3 examples, 0 failures
我们不允许插入的username或者email的长度超过固定的列的长度。这样的超出长度要求的spec测试看起来就像下面这样:
it \'prints error message if strings are too long\' do
long_username = \"a\"*33
long_email = \"a\"*256
script = [
\"insert 1 #{long_username} #{long_email}\",
\"select\",
\".exit\",
]
result = run_script(script)
expect(result).to match_array([
\"db > String is too long.\",
\"db > Executed.\",
\"db > \",
])
end
我了能够支持上面这种效果,我们需要升级我们的解析器(parser)。提醒一下,我们现在使用的是scanf():
if (strncmp(input_buffer->buffer, \"insert\", 6) == 0) {
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;
}
但是scanf()有一些缺点。如果读取的string大于正在读取它的缓存(buffer),就会引起缓存溢出(buffer overflow)并写入到意想不到的地方。所以我们需要在拷贝string到Row结构前检查每一个string的长度。为了检查string长度,我们需要用空格分割输入。
我使用 strtok() 来做这些。如果你看到过程就会觉得它很容易理解:
译注: strtok: 字符串处理函数,char * strtok ( char * str, const char * delimiters ); 分解字符串为一组字符串。str为要分解的字符,delimiters为分隔符字符(如果传入字符串,则传入的字符串中每个字符均为分割符)
+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;
}
每当输入到一个分隔符时(在我们的例子中就是空格),就在输入缓冲(input buffer)上连续调用strtok(),把它分解成子字符串。它返回一个指向子字符串开始位置的指针。
我们可以在每个文本值上调用strlen(),看看它是否太长(strlen()函数,获取字符串的长度)。
我们可以像处理其他错误码一样处理错误:
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;
这样就能通过测试了。
bundle exec rspec
....
Finished in 0.02284 seconds (files took 0.116 seconds to load)
4 examples, 0 failures
到了这里,我们不妨再多处理一个错误情况(id值插入一个负值):
it \'prints an error message if id is negative\' do
script = [
\"insert -1 cstack foo@bar.com\",
\"select\",
\".exit\",
]
result = run_script(script)
expect(result).to match_array([
\"db > ID must be positive.\",
\"db > Executed.\",
\"db > \",
])
end
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;
好了,测试做的差不多了。接下来是非常重要的功能:持久化!我们要实现保存我们的数据库到一个文件,再把它从文件中读取出来。(目前它还在内存当中)
现在它越来越牛了。
下面是和上一部分代码,修改位置的对比:
@@ -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;
并且我们添加了一些测试:
+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
+
+ it \'inserts and retrieves a row\' do
+ result = run_script([
+ \"insert 1 user1 person1@example.com\",
+ \"select\",
+ \".exit\",
+ ])
+ expect(result).to match_array([
+ \"db > Executed.\",
+ \"db > (1, user1, person1@example.com)\",
+ \"Executed.\",
+ \"db > \",
+ ])
+ end
+
+ 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
+
+ it \'allows inserting strings that are the maximum length\' do
+ long_username = \"a\"*32
+ long_email = \"a\"*255
+ script = [
+ \"insert 1 #{long_username} #{long_email}\",
+ \"select\",
+ \".exit\",
+ ]
+ result = run_script(script)
+ expect(result).to match_array([
+ \"db > Executed.\",
+ \"db > (1, #{long_username}, #{long_email})\",
+ \"Executed.\",
+ \"db > \",
+ ])
+ end
+
+ it \'prints error message if strings are too long\' do
+ long_username = \"a\"*33
+ long_email = \"a\"*256
+ script = [
+ \"insert 1 #{long_username} #{long_email}\",
+ \"select\",
+ \".exit\",
+ ]
+ result = run_script(script)
+ expect(result).to match_array([
+ \"db > String is too long.\",
+ \"db > Executed.\",
+ \"db > \",
+ ])
+ end
+
+ it \'prints an error message if id is negative\' do
+ script = [
+ \"insert -1 cstack foo@bar.com\",
+ \"select\",
+ \".exit\",
+ ]
+ result = run_script(script)
+ expect(result).to match_array([
+ \"db > ID must be positive.\",
+ \"db > Executed.\",
+ \"db > \",
+ ])
+ end
+end
Enjoy GreatSQL 😃
关于 GreatSQL
GreatSQL是由万里数据库维护的MySQL分支,专注于提升MGR可靠性及性能,支持InnoDB并行查询特性,是适用于金融级应用的MySQL分支版本。
相关链接: GreatSQL社区 Gitee GitHub Bilibili
GreatSQL社区:
欢迎来GreatSQL社区发帖提问
https://greatsql.cn/
技术交流群:
微信:扫码添加
GreatSQL社区助手
微信好友,发送验证信息加群
。
来源:https://www.cnblogs.com/greatsql/p/16755684.html
本站部分图文来源于网络,如有侵权请联系删除。