mongodb: “invalid character ',' looking for beginning of value”

一个超大的json（也就800M），需要导入mongodb，然后遇到了一个问题：

$ mongoimport --db weibo --collection data --file test.json
2018-05-09T16:10:22.357+0800    connected to: localhost
2018-05-09T16:10:22.360+0800    Failed: error processing document #2: invalid character ',' looking for beginning of value
2018-05-09T16:10:22.360+0800    imported 0 documents

first

一开始，我先去菜鸟工具1验证了一下我的json格式不是不是正确，json格式是没有没问题的。

second

我以为是编码的问题，可能是mac下的编码有问题，因为stackoverflow2有一个谈论这个问题的。上边的回复说是有UTF8不支持的字符，但是他们遇到的问题都是\\，我还是去Windows服务器上装上了mongodb，然后还是这个问题，可见我这个可能不是字符问题。
其中JP Lew遇到了也是,的问题提到的这个做法很不错，使用-vvvv这个参数确定位置。

$ mongoimport --db weibo --collection data --file test.json -vvvvv
2018-05-09T16:30:09.538+0800    using 4 decoding workers
2018-05-09T16:30:09.539+0800    using 1 insert workers
2018-05-09T16:30:09.539+0800    will listen for SIGTERM, SIGINT, and SIGKILL
2018-05-09T16:30:09.542+0800    filesize: 823127226 bytes
2018-05-09T16:30:09.542+0800    using fields:
2018-05-09T16:30:09.552+0800    connected to: localhost
2018-05-09T16:30:09.552+0800    ns: weibo.data
2018-05-09T16:30:09.552+0800    connected to node type: standalone
2018-05-09T16:30:09.553+0800    standalone server: setting write concern w to 1
2018-05-09T16:30:09.553+0800    using write concern: w='1', j=false, fsync=false, wtimeout=0
2018-05-09T16:30:09.553+0800    standalone server: setting write concern w to 1
2018-05-09T16:30:09.553+0800    using write concern: w='1', j=false, fsync=false, wtimeout=0
2018-05-09T16:30:09.555+0800    Failed: error processing document #2: invalid character ',' looking for beginning of value
2018-05-09T16:30:09.555+0800    imported 0 documents

嗯，还是这个问题，所以我这个问题应该跟JP的那个也不一样。而且我这个应该是第一个json就出问题了！

插曲

因为文件里好多东西都没用，所以我想只把有用的那几行挑出来，但是结果感人，还是想个正经办法把。
附上 cat+grep提取个别行3：

[root@localhost test]# cat test.txt 

hnlinux

peida.cnblogs.com

ubuntu

ubuntu linux

redhat

Redhat

linuxmint

[root@localhost test]# cat test2.txt 

linux

Redhat

[root@localhost test]# cat test.txt | grep -f test2.txt

hnlinux

ubuntu linux

Redhat

linuxmint

third

最后，在我一次又一次的实验下，终于找到了问题：

{
    ...
},
{
    ...
},
...

泥煤两个json中间多了一个逗号啊,然后写了一个脚本把这个逗号去掉吧。。。

import os
import re
import sys

args = sys.argv
if len(args) != 3 or args[1] == args[2]:
    raise Warning()
abs_path = os.path.abspath('.')
org_path = os.path.join(abs_path, args[1])
new_path = os.path.join(abs_path, args[2])
re_com = re.compile(r'^},')

try:
    fr = open(org_path, 'r')
    fw = open(new_path, 'w')
    for line in fr:
        if re_com.match(line):
            line = '}\n'
        fw.writelines(line)
except IOError as e:
    print(e)
finally:
    if fr:
        fr.close()
    if fw:
        fw.close()

这么pythonic的处理大文件的方式来自：https://www.cnblogs.com/wulaa... ：

with open(filename, 'r') as file:
    for line in file:
        ....

ok,把新文件导入进去～

$ mongoimport --db weibo --collection data --file new.json
2018-05-09T15:58:36.211+0800    connected to: localhost
2018-05-09T15:58:39.194+0800    [##......................] weibo.data77.5MB/785MB (9.9%)
2018-05-09T15:58:42.195+0800    [####....................] weibo.data160MB/785MB (20.4%)
2018-05-09T15:58:45.195+0800    [#######.................] weibo.data243MB/785MB (31.0%)
2018-05-09T15:58:48.203+0800    [#########...............] weibo.data323MB/785MB (41.1%)
2018-05-09T15:58:51.197+0800    [############............] weibo.data402MB/785MB (51.2%)
2018-05-09T15:58:54.195+0800    [##############..........] weibo.data478MB/785MB (60.9%)
2018-05-09T15:58:57.196+0800    [#################.......] weibo.data560MB/785MB (71.4%)
2018-05-09T15:59:00.195+0800    [###################.....] weibo.data642MB/785MB (81.8%)
2018-05-09T15:59:03.196+0800    [######################..] weibo.data722MB/785MB (92.0%)
2018-05-09T15:59:05.521+0800    [########################] weibo.data785MB/785MB (100.0%)
2018-05-09T15:59:05.522+0800    imported 95208 documents