i32 limit in JSON stats

[alfredolainez]

Environment

Delta-rs version: 0.18.2

Binding: Python

Environment:

• Cloud provider: AWS
• OS: Amazon Linux 2

---

Bug

What happened:

When reading a DeltaLake table from Polars using pl.read_delta, I get the following error:

DeltaProtocolError: Invalid JSON in file stats: invalid value: integer 4051124561, expected i32 at line 1 column 70

which ultimately comes from deltalake:

What you expected to happen: My code in Python can successfully read other tables, it is just this particular table that throws this problem. The particular table where this happens is frequently accessed and I can read it successfully through Spark, so I was expecting to read it as well from deltalake. Not sure if the int32 limitation is part of the protocol or the library should allow for bigger int types.

[sherlockbeard]

can you share a reproducible example ?.
or your json commit file (make sure there is no personal secret information )

below code is working fine

import polars as pl

pl_df = pl.DataFrame({
    "x": [4051124561, 4051124564, 4051124563],
    "y": [4051124561, 4051124564, 4051124563],
    "z": [4051124561, 4051124564, 4051124563],
})

pl_df.write_delta('./temp2')

pl_df = pl.read_delta('./temp2')

print(pl_df)

[alfredolainez]

Thank for your example @sherlockbeard , I can confirm that works fine for me as well.

I have been trying to find the offending JSON file in the _delta_log folder but the table is massive and there are thousands of json commit files + parquet checkpoint files. So many I can't even list the folder easily to do some string matching on the offending integer number. I can see this integer referenced in the error keeps changing and growing bigger, so hopefully I can limit the search to the _delta_log files that are read first. My error comes up very fast after executing the query, so I guess it must happen in one of the first metadata reads before starting to execute the query. What files are read first by deltalake so that I can limit my search to those? (my query is just a pl.read_delta referencing two partitions and a few columns)

[sherlockbeard]

delta table reads the last checkpoint and json's created after that

there should be a _last_checkpoint file in _delta_log folder
it contains data like {"size":6,"size_in_bytes":20619,"version":3}
in this case version 3 is my last checkpoint .
and all the json's after that (from 00000000000000000004.json to latest json )

after that you can select json's like

tablePath = "temp4" 
start = "/_delta_log/"
jsonStart = 4
totalFile = 50

for i in range(int(jsonStart), int(jsonStart) + totalFile + 1):
    path = tablePath + start + str(i).zfill(20) + ".json"
    print(path)
    # open and read file for the value

[alfredolainez]

Big thanks Sherlock, found the culprit!

This is the JSON in _last_checkpoint

{'version': 435104,
 'size': 14292411,
 'parts': 286,
 'sizeInBytes': 4563187026,
 'numOfAddFiles': 9857205,
 'checkpointSchema': {big table schema},
 'checksum': '834a34e25536b983308deb6ce9bb8df4'}

sizeInBytes is the number I get as invalid. Seems the library might not be expecting this big of a checkpoint?

[sherlockbeard]

hey @alfredolainez in the bug the number is 4051124561

edited my _last_checkpoint size_in_bytes 4563187026 and still able to read it

[alfredolainez]

The table is being written to frequently so the number is changing. When I checked _last_checkpoint the number in sizeInBytes is the one I get in the error now 🙂.

[alfredolainez]

Interesting. I copied my _last_checkpoint file to the location in your example (/temp2) and I am able to reproduce the error.

Copying just this as the _last_checkpoint file seems to do the trick to get the DeltaProtocolError:

{"version":435195,"size":14337557,"parts":287,"sizeInBytes":4579627068,"numOfAddFiles":9902351}\n

For reference, I am using deltalake==0.18.2

[sherlockbeard]

yep using this able to reproduce

funny thing i tried with
{"size":10,"size_in_bytes": 4563187026,"version":7}
it worked fine can you try same in your /temp2 table

ok got the reason . just to confirm your table have deletion vectors ?.

[alfredolainez]

Using that resulted in a different error for me, I think my table is a bit different than yours. Seeing this issue (#1468) it seems that SizeInBytes is optional so probably that's why.

Not sure if the table has deletion vectors but I would imagine so since storage performance is critical here. Is there any way I can easily check?

[sherlockbeard]

@rtyler , @ion-elgreco fixing this will require change in delta portal DeletionVectorDescriptor field sizeInBytes from int to long.

[sherlockbeard]

now i am little confused but delta-rs doesn't support reading with deletion vector .
@alfredolainez what are you using to write the table ?. also were you previously able to read this table from polars ?

[alfredolainez]

I don't have a lot of details on how the table is written but as far as I understand it is Spark. This is the first time I am trying to read these tables with Polars, so not sure if it used to work before. However I can read other tables in the same lake successfully, and I can see the _last_checkpoint in those tables also contain the same sizeInBytes, but under the i32 limit. The tables do seem to have DeletionVectors in the checkPointSchema field, but I can read them fine except for this table where the main sizeInBytes field doesn't fit in i32.

Deletion vectors might be unrelated though, no? Our toy example shows the problem without them.

[sherlockbeard]

created a pr that is fixing the dummy example .
Will suggest you hit the slack #delta-rs once https://go.delta.io/slack your case is very strange