Segmentation fault when trying to load large json file

[eddie-dunn]

I have a 1.1GB json file that I try to load with pandas.json.load:

import pandas as pd
with open('/tmp/file.json') as fileh:
    text = pd.json.load(fileh)

It breaks with the following output

Error in `python3': double free or corruption (out): 0x00007ffe082171f0 ***

I can load the file with Pythons built-in json module. What is going wrong here?

[jreback]

you need to use read_json (or the built in json module). pd.json is not the same thing

[eddie-dunn]

I get the same segfault when using read_json.

[jreback]

well not sure how you generated it, its possible its not valid json / parseable by read_json

[eddie-dunn]

I've generated the json file with both Python's built-in json.dump and pandas.json.dump; same result.

json.load can read the file just fine, so the json should be valid.

[TomAugspurger]

Can you try to narrow it down to a smaller example that generates the segfault, and post that file?

[eddie-dunn]

1. This issue should be reopened
2. I extracted a subset of the json-file (~200MB) and read_json worked fine

As I said originally, I think the issue is with the size of the json file.

[TomAugspurger]

Can you

1. Join 5 or 6 of those 200MB sections into a larger one and try to read that
2. Work through the next 5 or 6 sections of the file in 200MB chunks

and see if either of those fail?
It shouldn't be segfaulting, but we'll need a reproducible example before we can start to diagnose where the bug is.

[eddie-dunn]

I realized that the subset only took 200MB of RAM when loaded in the REPL. Once dumped to a json file on disk it was much smaller. 4 joined subsets did not present a problem for read_json as the resulting json file was only 321 MB.

I incremented the number of subsets; 7 subsets at 561 MB, 11 at 881 MB worked fine. 14 joined subsets at 1.1 GB crashed ipython:

In [44]: with open('/tmp/pandas14x.json') as fileh:    pand = pd.read_json(fileh)
   ....:     
*** Error in `/usr/bin/python3': double free or corruption (out): 0x00007ffedeb05b40 ***
[1]    4914 abort (core dumped)  ipython3

Might be worth your while to generate your own large json file to debug why read_json crashes Python if the json file is too big.

[jreback]

@eddie-dunn it would be really helpful for you to show a copy-pastable example that reproduces the problem. These cases are almost always a function of the dtypes of the structure you are saving.

This would make debugging much easier, as this is the first report I have ever seen for this type of bug.

Further pls show pd.show_versions().

[eddie-dunn]

Generate example code:

#!/usr/bin/env python3
import json
import sys

SIZE = int(5e7)

FILENAME = 'generated.json'

print("Generating json with {} elements...".format(SIZE))
mdict = {key: val for key, val in zip(range(SIZE), range(SIZE))}

print("Dumping json to {}...".format(FILENAME))
with open(FILENAME, 'w') as fileh:
    json.dump(mdict, fileh)

Test run example code:

#!/usr/bin/env python3
import json
import pandas as pd
import sys


FILENAME = 'generated.json'

try:
    PANDAS = False if sys.argv[1] == 'n' else True
except IndexError:
    PANDAS = True

print("Loading json{}...".format(" with pandas" if PANDAS else ""))
with open(FILENAME) as fileh:
    if PANDAS:
        pd.json.load(fileh)
    else:
        json.load(fileh)  # set PANDAS=False and it will work

print("You see this, it worked!")

Please note that if you try to run the script with PANDAS=False you will need approximately 8 GB RAM or it will exit with an out of memory exception.

pandas.show_versions():

INSTALLED VERSIONS
------------------
commit: None
python: 3.4.3.final.0
python-bits: 64
OS: Linux
OS-release: 3.13.0-63-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8

pandas: 0.15.2
nose: 1.3.4
Cython: None
numpy: 1.8.2
scipy: 0.13.3
statsmodels: None
IPython: 3.2.0
sphinx: None
patsy: None
dateutil: 2.4.0
pytz: 2014.10
bottleneck: None
tables: None
numexpr: None
matplotlib: 1.3.1
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: 0.999
httplib2: 0.8
apiclient: None
rpy2: None
sqlalchemy: None
pymysql: None
psycopg2: None

[jreback]

pls try this with 0.17.0 and report back.

[TomAugspurger]

I can reproduce it 0.17.

[eddie-dunn]

Yes, pandas still segfaults on 0.17.

[jreback]

ok will reopen if anyone cares to dig into the c-code

@kawochen

[kawochen]

Will hopefully submit a PR tonight

[jreback]

xref #7641 as well

[jreback]

cc @Komnomnomnom

[jreback]

does #11393 fix for you? (you have to build from the PR to test)

[adri0]

I'm also having a segmentation fault when using 'read_csv' method to load a file with around 160Mb in pandas 0.17.0.
When I downgrade to 0.16.2 it works fine.

[TomAugspurger]

@adri0 read_csv uses different C code that read_json, so that's probably a separate bug. Could you make a new issue for that, with an example that reproduces the segfault?

[adri0]

Okay, thanks. I just opened #11419