Question

我正在使用两种方法来r / w sqlite表：

+ (NSString *) getWeatherData:(int)rowID:(int)columnID {
    NSString *savedWeatherData = [[NSString alloc] init];
    if (sqlite3_open([[DBController getDBPath] UTF8String], &database) == SQLITE_OK) {

        const char *sql = "select * from TABLE where id=?";
        sqlite3_stmt *selectstmt;
        if(sqlite3_prepare_v2(database, sql, -1, &selectstmt, NULL) == SQLITE_OK) {

            sqlite3_bind_int(selectstmt, 1, rowID);

            while(sqlite3_step(selectstmt) == SQLITE_ROW) {

                NSInteger primaryKey = sqlite3_column_int(selectstmt, 0); 
                Weather *weatherObj = [[Weather alloc] initWithPrimaryKey:primaryKey];

                weatherObj.weatherData = [NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, columnID)];
                savedWeatherData = weatherObj.weatherData;
                [weatherObj release];
            }

        }   
    }
    return [savedWeatherData autorelease];
}

并保存一些数据：

+ (void) saveDataToDataBase:(NSString *)columnToUpdate:(int)rowID:(NSString *)value {

    if (sqlite3_open([[DBController getDBPath] UTF8String], &database) == SQLITE_OK) {

        updateStmt = nil;

        NSString *sqlString = [[@"update TABLE set " stringByAppendingString:columnToUpdate] stringByAppendingString:@"=? where id=?"];

        const char *sql = [sqlString UTF8String];

        if(sqlite3_prepare_v2(database, sql, -1, &updateStmt, NULL) != SQLITE_OK) {
            NSAssert1(0, @"Error while creating update statement. '%s'", sqlite3_errmsg(database));
        } else { // select statement ok

            sqlite3_bind_text(updateStmt, 1, [value UTF8String], -1, SQLITE_TRANSIENT); // replace first ? with value
            sqlite3_bind_int(updateStmt, 2, rowID);                                     // replace second ? with rowID

            if(SQLITE_DONE != sqlite3_step(updateStmt)) {
                NSAssert1(0, @"Error while updating. '%s'", sqlite3_errmsg(database));
            } else {
               // NSLog(@"Update completed !!!");  
            }

            sqlite3_reset(updateStmt);
        }

        sqlite3_finalize(updateStmt);

    }
    else
    sqlite3_close(database); //Even though the open call failed, close the database connection to release all the memory.

}

使用Instruments，我发现sqlite的内存消耗非常大。信息：在app启动期间，cca将100种不同类型的数据存储在DB中 - 对于每个数据，调用此saveDataToDataBase方法。（如果没有互联网连接 - 将使用getWeatherData - 并且将再次读取cca 100种不同类型的数据）

请你能告诉我 - 是否可以优化内存消耗。

非常感谢！

亲切的问候！

Answer 1

您需要确定selectstmt。此外，您不应该在每次通话时打开和关闭数据库。保持对数据库的引用，只有当你真的不再需要它时才关闭它。（第一种方法每次都不会关闭数据库。）

此外，您可以在打开数据库后设置缓存大小：

// Modify cache size so we don't overload memory. 50 * 1.5kb
if (sqlite3_exec(database, "PRAGMA CACHE_SIZE=50;", NULL, NULL, NULL) !
= SQLITE_OK) {
NSAssert1(0, @"Error: failed to set cache size with message '%s'.",
sqlite3_errmsg(database));
}

sqlite请求的内存优化 - 需要帮助

1 个答案: