/*
功能:按名次查找记录
参数: 姓名name,from 从第几个开始查找, 从0 到 count-1
返回值: int 型, 找到的记录在表中的位置, 没有找到则返回-1
打印: 无
*/
int rank_findRecord(int rank, int from)
{
int i;
int index = -1;
int flag = 0;
int count = countRecords();
rank_Refresh();
for(i=from; i<count; i++)
{
if( records[i].rank == rank) // 按指定的名次来查询
{
flag = 1;
index = i + 1;
break;
}
}
if(flag == 0)
{
return (index);
}
else
{
return (index);
}
}
void QgsSearchQueryBuilder::on_btnOk_clicked()
{
// if user hits OK and there is no query, skip the validation
if ( txtSQL->text().trimmed().length() > 0 )
{
accept();
return;
}
// test the query to see if it will result in a valid layer
long numRecs = countRecords( txtSQL->text() );
if ( numRecs == -1 )
{
// error shown in countRecords
}
else if ( numRecs == 0 )
{
QMessageBox::warning( this, tr( "No Records" ), tr( "The query you specified results in zero records being returned." ) );
}
else
{
accept();
}
}
/*
功能:按学号查找记录
参数: 姓名name,from 从第几个开始查找, 从0 到 count-1
返回值: int 型, 找到的记录在表中的位置, 没有找到则返回-1
打印: 无
*/
int num_findRecord(char *num, int from)
{
int count = 0;
int index = -1;
int i = 0;
int flag = 0; //找到与否的标志
count = countRecords();
for(i=from; i<count; i++)
{
if( strcmp(records[i].num, num) == 0 ) // 按指定的学号来查询
{
flag = 1;
index = i + 1;
break;
}
}
if(flag == 0)
{
return (index);
}
else
return (index);
}
void QgsSearchQueryBuilder::on_btnTest_clicked()
{
long count = countRecords( txtSQL->text() );
// error?
if ( count == -1 )
return;
QMessageBox::information( this, tr( "Search results" ), tr( "Found %n matching feature(s).", "test result", count ) );
}
/*
功能：判断内存数组是否大小不够，不够的话自动增大INCR_SIZE
参数：无
返回：无
打印：使用条件编译，若定义了DEBUG则打印“数据库自动增大成功, 当前数据库大小为%d!”，便于调试
*/
void autoIncr()
{
int count = countRecords();
if(count >= arrSize)
{
records = (StuInfo*) realloc( records, (arrSize+INCR_SIZE)*sizeof(StuInfo) ); // 当数据库大小不够时，每次自动增加INCR_SIZE
if(records == NULL)
{
printf("memory failed!");
exit(-1);
}
arrSize = arrSize + INCR_SIZE;
#ifdef DEBUG
{
printf("\n数据库自动增大成功, 当前数据库大小为%d! \n", arrSize);
}
#endif
}
}
/*
功能：判断新增加的学生的学号是否与内存中已有的学生学号冲突，冲突时给出提示
参数：要判断的学生
返回：当没有与其他学生重复时返回0，有重复时返回1
*/
int dunum(StuInfo *stu)
{
int count = countRecords();
int i;
int flag = 0;
int du = 0; // 要判断的学生的学号与已有学生学号（包括自己）相比较，学号重复的次数，若du最后大于或等于2，则说明有重复
for(i=0; i<count; i++)
{
if( strcmp(stu->num, records[i].num) == 0)
{
++du;
}
}
if(du == 2 || du > 2)
{
printf("\n输入的学号与其他学生重复!\n");
flag = 1;
}
return flag;
}
/*
功能:根据指定的序号显示出记录信息
参数:index,指定的序号
返回:void
指定的序号不存在时给出找不到的信息
*/
void index_disPlay(int index)
{
int count = countRecords();
if( index > count ) // 输入不合法时
{
printf("内存中没有该杀记录!\n");
}
else if( index < 1 ) // 输入不合法时
printf("给定的序号不能为0或负数!\n");
else
{
if(records[index-1].savetag == 1)
{
showTable();
PR(index-1); // 宏定义
}
else
{
printf("内存中没有该杀记录!\n"); // 找不到时相应处理
}
}
}
/*
功能:按姓名查找记录
参数: 姓名name,from 从第几个开始查找, 从0 到 count-1
返回值: int 型, 找到的记录在表中的位置, 没有找到则返回-1
打印: 无
*/
int name_findRecord(char *name, int from)
{
int count = 0; //内存中学生记录数
int index = -1; // 位置标记
int i = 0;
int flag = 0; //找到与否的标志，找到记录后为1
count = countRecords(); //调用记录统计函数，得出内存中当前的记录的条数
for(i=from; i<count; i++)
{
if( strcmp(records[i].name, name) == 0 ) //将内存中的记录逐条与要查找的记录比较
{
flag = 1; // 如果找到则flag置为1
index = i + 1; // index 为该记录在内存中的位置，以1为起始
break; //退出循环
}
}
if(flag == 0) // flag为0则表示没有找到指定的记录
{
return (index);
}
else
return (index);
}
// A function that performs a series of writes to a
// Berkeley DB database. The information written
// to the database is largely nonsensical, but the
// mechanism of transactional commit/abort and
// deadlock detection is illustrated here.
void *
writerThread(void *args)
{
int j, thread_num;
int max_retries = 20; // Max retry on a deadlock
const char *key_strings[] = {"key 1", "key 2", "key 3", "key 4",
"key 5", "key 6", "key 7", "key 8",
"key 9", "key 10"};
Db *dbp = (Db *)args;
DbEnv *envp = dbp->get_env();
// Get the thread number
(void)mutex_lock(&thread_num_lock);
global_thread_num++;
thread_num = global_thread_num;
(void)mutex_unlock(&thread_num_lock);
// Initialize the random number generator
srand(thread_num);
// Perform 50 transactions
for (int i=0; i<50; i++) {
DbTxn *txn;
bool retry = true;
int retry_count = 0;
// while loop is used for deadlock retries
while (retry) {
// try block used for deadlock detection and
// general db exception handling
try {
// Begin our transaction. We group multiple writes in
// this thread under a single transaction so as to
// (1) show that you can atomically perform multiple
// writes at a time, and (2) to increase the chances
// of a deadlock occurring so that we can observe our
// deadlock detection at work.
// Normally we would want to avoid the potential for
// deadlocks, so for this workload the correct thing
// would be to perform our puts with autocommit. But
// that would excessively simplify our example, so we
// do the "wrong" thing here instead.
txn = NULL;
envp->txn_begin(NULL, &txn, 0);
// Perform the database write for this transaction.
for (j = 0; j < 10; j++) {
Dbt key, value;
key.set_data((void *)key_strings[j]);
key.set_size((u_int32_t)strlen(key_strings[j]) + 1);
int payload = rand() + i;
value.set_data(&payload);
value.set_size(sizeof(int));
// Perform the database put
dbp->put(txn, &key, &value, 0);
}
// countRecords runs a cursor over the entire database.
// We do this to illustrate issues of deadlocking
std::cout << thread_num << " : Found "
<< countRecords(dbp, txn)
<< " records in the database." << std::endl;
std::cout << thread_num << " : committing txn : " << i
<< std::endl;
// commit
try {
txn->commit(0);
retry = false;
txn = NULL;
} catch (DbException &e) {
std::cout << "Error on txn commit: "
<< e.what() << std::endl;
}
} catch (DbDeadlockException &) {
// First thing that we MUST do is abort the transaction.
if (txn != NULL)
(void)txn->abort();
// Now we decide if we want to retry the operation.
// If we have retried less than max_retries,
// increment the retry count and goto retry.
if (retry_count < max_retries) {
std::cerr << "############### Writer " << thread_num
<< ": Got DB_LOCK_DEADLOCK.\n"
<< "Retrying write operation." << std::endl;
retry_count++;
retry = true;
} else {
// Otherwise, just give up.
std::cerr << "Writer " << thread_num
<< ": Got DeadLockException and out of "
<< "retries. Giving up." << std::endl;
retry = false;
}
} catch (DbException &e) {
std::cerr << "db put failed" << std::endl;
std::cerr << e.what() << std::endl;
if (txn != NULL)
txn->abort();
retry = false;
} catch (std::exception &ee) {
std::cerr << "Unknown exception: " << ee.what() << std::endl;
return (0);
}
}
}
return (0);
}
