Question

现在我有一个聚合管道返回以下数组：

[{
    "_id": 1,
    "items": {
        "_id": 1,
        "transactions": []
    }
  },
{
    "_id": 2,
    "items": {
        "_id": 2,
        "transactions": [
            {
                "_id": "5a536dc1bc9b2113986a9047",
                "price": 5.56
            },
            {
                "_id": "5a536e1bbc9b2113986a904e",
                "price": 11.56,
            }
        ]
    }
},
{
    "_id": 3,
    "items": {
        "_id": 1,
        "transactions": []
    }
}]

可以过滤字段＆＃34;事务＆＃34;在子文档＆＃34;项目＆＃34;不是空的。像这样：

[{
    "_id": 2,
    "items": {
        "_id": 2,
        "transactions": [
            {
                "_id": "5a536dc1bc9b2113986a9047",
                "price": 5.56
            },
            {
                "_id": "5a536e1bbc9b2113986a904e",
                "price": 11.56,
            }
        ]
    }
}]

汇总管道不是用于查询

Answer 1

在聚合管道中，最后添加import pygame as pg def main(): screen = pg.display.set_mode((640, 480)) clock = pg.time.Clock() white = pg.Color('white') x_change = 0 y_change = 0 x = 400 y = 400 # Load the images before the main loop starts. You could also # do this in the global scope. right_images = [] for img_name in ['knight_right.png','knight_right1.png','knight_right2.png']: right_images.append(pg.image.load(img_name).convert_alpha()) left_images = [] for img_name in ['knight_left.png', 'knight_left1.png', 'knight_left2.png']: left_images.append(pg.image.load(img_name).convert_alpha()) # This variable refers to the currently selected image list. active_images = left_images counter = 0 # There's no need for a second counter. player = active_images[counter] # Currently active animation frame. while True: for event in pg.event.get(): if event.type == pg.QUIT: return elif event.type == pg.KEYDOWN: if event.key == pg.K_d: x_change = 5 active_images = right_images # Swap the image list. elif event.key == pg.K_a: x_change = -5 active_images = left_images # Swap the image list. elif event.key == pg.K_w: y_change -= 5 elif event.key == pg.K_s: y_change += 5 elif event.type == pg.KEYUP: if event.key == pg.K_d and x_change > 0: x_change = 0 counter = 0 # Switch to idle pose. player = active_images[counter] elif event.key == pg.K_a and x_change < 0: x_change = 0 counter = 0 # Switch to idle pose. player = active_images[counter] elif event.key == pg.K_w and y_change < 0: y_change = 0 elif event.key == pg.K_s and y_change > 0: y_change = 0 if x_change != 0: # If moving. # Increment the counter and keep it in the correct range. counter = (counter+1) % len(active_images) player = active_images[counter] # Swap the image. x += x_change y += y_change screen.fill(white) screen.blit(player, (x, y)) pg.display.flip() clock.tick(30) if __name__ == '__main__': pg.init() main() pg.quit()管道以根据事务数组大小进行过滤

$match

输出

> db.foo.aggregate([{$match : {"items.transactions" : { $gt : {$size : 0}}}}]).pretty()

示例文件

{
    "_id" : 2,
    "items" : {
        "_id" : 2,
        "transactions" : [
            {
                "_id" : "5a536dc1bc9b2113986a9047",
                "price" : 5.56
            },
            {
                "_id" : "5a536e1bbc9b2113986a904e",
                "price" : 11.56
            }
        ]
    }
}
>

使用数组字段筛选子文档不为空

1 个答案: