Sqlite3实现脏读

参考文档 http://www.sqlite.org/sharedcache.html
sqlite3实现脏读需要进行如下配置：

(A) 打开共享cache， 调用sqlite3接口sqlite3_enable_shared_cache(1)。

(B) 执行语句"PRAGMA read_uncommitted = TRUE"。

#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <cassert>
#include <thread>

#include "sqlite3.h"

static const char* kDatabaseName = "test.db";

static bool OpenDB(const char* path, sqlite3** db) {
assert(db != NULL);

sqlite3_enable_shared_cache(1);

int rc = sqlite3_open(path, db);
if (rc != SQLITE_OK) {
std::cout << "Failed to open " << kDatabaseName << std::endl;
std::cout << "Error msg: " << sqlite3_errmsg(*db) << std::endl;
return false;
}

sqlite3_exec(*db, "PRAGMA read_uncommitted = TRUE", NULL, NULL, NULL);

return true;
}

static void PrepareTable() {
sqlite3* db = NULL;

if (!OpenDB(kDatabaseName, &db)) {
return;
}

const char* kCreateTableSql = "CREATE TABLE DIRTYREAD_TEST(ID INT);";
char* error_msg = NULL;

int rc = sqlite3_exec(db, kCreateTableSql, NULL, NULL, &error_msg);
if (rc != SQLITE_OK) {
std::cout << "Failed to create table!" << std::endl;
std::cout << "Error msg: " << error_msg << std::endl;
sqlite3_free(error_msg);
}

sqlite3_close(db);
}

static void ClearTable() {
sqlite3* db = NULL;
if (!OpenDB(kDatabaseName, &db)) {
return;
}

const char* kClearTableSql = "DELETE FROM DIRTYREAD_TEST;";
char* error_msg = NULL;

int rc = sqlite3_exec(db, kClearTableSql, NULL, NULL, &error_msg);
if (rc != SQLITE_OK) {
std::cout << "Failed to clear table!" << std::endl;
std::cout << "Error msg: " << error_msg << std::endl;
sqlite3_free(error_msg);
}

sqlite3_close(db);
}

static void InsertData() {
sqlite3* db = NULL;
if (!OpenDB(kDatabaseName, &db)) {
return;
}

const char* kInsertDataSql = "INSERT INTO DIRTYREAD_TEST VALUES(?);";

sqlite3_exec(db, "begin", NULL, NULL, NULL);

sqlite3_stmt* stmt = NULL;
sqlite3_prepare_v2(db, kInsertDataSql, strlen(kInsertDataSql), &stmt, NULL);

for (int i = 0; i < 10000000; i++) {
sqlite3_reset(stmt);
sqlite3_bind_int(stmt, 1, i);
int rc = sqlite3_step(stmt);
if (rc != SQLITE_DONE) {
std::cout << "Failed to execute sql when insert " << i << "!" << std::endl;
std::cout << "Error code: " << sqlite3_errcode(db) << std::endl;
std::cout << "Error msg: " << sqlite3_errmsg(db) << std::endl;
break;
}
}

sqlite3_finalize(stmt);

sqlite3_exec(db, "commit", NULL, NULL, NULL);

sqlite3_close(db);
}

static int SelectCallback(void* data, int col_count, char** col_values, char** col_names) {
for (int i = 0; i < col_count; ++i) {
if (col_values[i] == NULL) {
continue;
}

std::cout << col_names[i] << " = " << col_values[i] << std::endl;
}

return 0;
}

static void ReadData() {
sqlite3* db = NULL;
if (!OpenDB(kDatabaseName, &db)) {
return;
}

const char* kSelectSql = "SELECT * FROM DIRTYREAD_TEST WHERE ID = 1;";
char* error_msg = NULL;

for (int i = 0; i < 1000; i++) {
int rc = sqlite3_exec(db, kSelectSql, SelectCallback, NULL, &error_msg);
if (rc == SQLITE_OK) {
std::cout << "Select successfully!" << std::endl;
} else {
std::cout << "Select failed! Error msg: " << error_msg << std::endl;
sqlite3_free(error_msg);
}
}

sqlite3_close(db);
}

int main4() {
//PrepareTable();
ClearTable();

std::thread thread1(InsertData);
std::thread thread2(ReadData);

thread1.join();
thread2.join();

return 0;
}