FMResultSet 是否需要关闭

问题

• 问题代码

  FMDatabaseQueue *queue = [DBUtilities shareDBqueue];
    //先执行del在插入
    //注:此处用事务
    
    [queue inTransaction:^(FMDatabase *db, BOOL *rollback) {
       
        for(TestDoInfo *testdo in tempTestDoAdd){
            checksql = [NSString stringWithFormat:kSQLExistsGreaterAddTimeWithTestdo,(long)testdo.testDoID,(long)testdo.carType,(long)testdo.subjectType,testdo.add_time];
            FMResultSet *resultSet = [db executeQuery:checksql];
            
            if (resultSet== nil || !resultSet.next) {
                insertsql = [DBUtilitiesSQLHelper insertSQLWithObject:testdo];
                
                updateSuccess = [db executeUpdate:insertsql];
                
                if (!updateSuccess) {
                    *rollback = YES;
                }else{
                    if (!testdo.is_show_in_wrong) {
                        updateSuccess = [db executeUpdate:[NSString stringWithFormat:@"update test_do set my_answer = (SELECT AnswerTrue FROM web_note where ID = %ld) where test_id = %ld and car_type = %ld and kemu_type = %ld ",(long)testdo.testDoID,(long)testdo.testDoID,(long)testdo.carType,(long)testdo.subjectType]];
                        
                        if (!updateSuccess) {
                            *rollback = YES;
                        }
                    }
                }
            }
        }
    }];

• 错误在使用FMDB执行查询时未关闭返回结果集（FMResultSet）

• 解决方案(手动关闭结果集)

if (resultSet != nil) {
   [resultSet close];
}

• GitHub-issues: https://github.com/ccgus/fmdb/issues/692

相关知识点

1.result.next

- (BOOL)next {
    return [self nextWithError:nil];
}

- (BOOL)nextWithError:(NSError **)outErr {
    
    int rc = sqlite3_step([_statement statement]);
    
    if (SQLITE_BUSY == rc || SQLITE_LOCKED == rc) {
        NSLog(@"%s:%d Database busy (%@)", __FUNCTION__, __LINE__, [_parentDB databasePath]);
        NSLog(@"Database busy");
        if (outErr) {
            *outErr = [_parentDB lastError];
        }
    }
    else if (SQLITE_DONE == rc || SQLITE_ROW == rc) {
        // all is well, let's return.
    }
    else if (SQLITE_ERROR == rc) {
        NSLog(@"Error calling sqlite3_step (%d: %s) rs", rc, sqlite3_errmsg([_parentDB sqliteHandle]));
        if (outErr) {
            *outErr = [_parentDB lastError];
        }
    }
    else if (SQLITE_MISUSE == rc) {
        // uh oh.
        NSLog(@"Error calling sqlite3_step (%d: %s) rs", rc, sqlite3_errmsg([_parentDB sqliteHandle]));
        if (outErr) {
            if (_parentDB) {
                *outErr = [_parentDB lastError];
            }
            else {
                // If 'next' or 'nextWithError' is called after the result set is closed,
                // we need to return the appropriate error.
                NSDictionary* errorMessage = [NSDictionary dictionaryWithObject:@"parentDB does not exist" forKey:NSLocalizedDescriptionKey];
                *outErr = [NSError errorWithDomain:@"FMDatabase" code:SQLITE_MISUSE userInfo:errorMessage];
            }
            
        }
    }
    else {
        // wtf?
        NSLog(@"Unknown error calling sqlite3_step (%d: %s) rs", rc, sqlite3_errmsg([_parentDB sqliteHandle]));
        if (outErr) {
            *outErr = [_parentDB lastError];
        }
    }
    
    
    if (rc != SQLITE_ROW) {
        [self close];
    }
    
    return (rc == SQLITE_ROW);
}

• sqlite3_step返回值

SQLITE_OK = 0; 返回成功

SQLITE_ERROR = 1; SQL错误或错误的数据库

SQLITE_INTERNAL = 2; An internal logic error in SQLite

SQLITE_PERM = 3; 拒绝访问

SQLITE_ABORT = 4; 回调函数请求中断

SQLITE_BUSY = 5; 数据库文件被锁

SQLITE_LOCKED = 6; 数据库中的一个表被锁

SQLITE_NOMEM = 7; 内存分配失败

SQLITE_READONLY = 8; 试图对一个只读数据库进行写操作

SQLITE_INTERRUPT = 9; 由sqlite_interrupt()结束操作

SQLITE_IOERR = 10; 磁盘I/O发生错误

SQLITE_CORRUPT = 11; 数据库磁盘镜像畸形

SQLITE_NOTFOUND = 12; (Internal Only)表或记录不存在

SQLITE_FULL = 13; 数据库满插入失败

SQLITE_CANTOPEN = 14; 不能打开数据库文件

SQLITE_PROTOCOL = 15; 数据库锁定协议错误

SQLITE_EMPTY = 16; (Internal Only)数据库表为空

SQLITE_SCHEMA = 17; 数据库模式改变

SQLITE_TOOBIG = 18; 对一个表数据行过多

SQLITE_CONSTRAINT = 19; 由于约束冲突而中止

SQLITE_MISMATCH = 20; 数据类型不匹配

SQLITE_MISUSE = 21; 数据库错误使用

SQLITE_NOLFS = 22; 使用主机操作系统不支持的特性

SQLITE_AUTH = 23; 非法授权

SQLITE_FORMAT = 24; 辅助数据库格式错误

SQLITE_RANGE = 25; 2nd parameter to sqlite_bind out of range

SQLITE_NOTADB = 26; 打开的不是一个数据库文件

SQLITE_ROW = 100; sqlite_step() has another row ready

SQLITE_DONE = 101; sqlite_step() has finished executing

在- (BOOL)nextWithError:(NSError **)outErr中会判断sqlite3_step返回值如果不等于SQLITE_ROW（即无下一个数据）会自动关闭结果集（当前前提是你调用了next方法）

常用方式

• 自动关闭无需手动关闭

FMDatabaseQueue *queue = [DBUtilities shareDBqueue];

[queue inDatabase:^(FMDatabase *db) {
    FMResultSet *rs = [db executeQuery: weakSQL];

    while (rs.next) {
        NSInteger count = [rs intForColumn:@"totalCount"];
    }
    
}];

[queue inTransaction:^(FMDatabase *db, BOOL *rollback) {

    FMResultSet *rs1 = [db executeQuery: weakSQL1];
    while (rs1.next) {
        NSInteger count = [rs1 intForColumn:@"totalCount"];
    }

    FMResultSet *rs2 = [db executeQuery: weakSQL2];
    while (rs2.next) {
        NSInteger count = [rs2 intForColumn:@"totalCount"];
    }
}];

• 不使用while只要一个结果，并if判断需手动关闭

  __block NSInteger score = 0;
      NSString *sql = [[NSString alloc] initWithFormat:kSQLGETSubjectLastExampleScore,(long)subjectType,(long)carType];
        
        if (carType >=CarTypeCoach) {
            sql =[[NSString alloc] initWithFormat:kSQLGETCartypeLastExampleScore,(long)carType];
        }
        __weak NSString *weakSQL = sql;
        
        FMDatabaseQueue *queue = [DBUtilities shareDBqueue];
        [queue inDatabase:^(FMDatabase *db) {
            FMResultSet *rs = [db executeQuery: weakSQL];
            if(rs.next){
                score = [rs intForColumn:@"score"];
            }
            
            if (rs != nil) {
                [rs close];
            }
            
        }];
    return score;