Unable to read delta table created using Uniform

[jeppe742]

Environment

Delta-rs version: 0.17.4

Binding: Python

Environment:

• Cloud provider: N/A
• OS: Ubuntu
• Other:

---

Bug

What happened: We are investigating using Delta Uniform to have our Spark jobs also write Iceberg metadata. In order to enable the generation of Iceberg metadata you have to set the delta.enableIcebergCompatV2 property on the table. When you set this, the Delta transaction log will include some more information.

E.g if you run the Example from the Uniform documentation

CREATE TABLE uniform_table(c1 INT) USING DELTA TBLPROPERTIES(
  'delta.enableIcebergCompatV2' = 'true',
  'delta.universalFormat.enabledFormats' = 'iceberg');

You will get a delta transaction that looks something like this

{"commitInfo":{"timestamp":1717753754287,"operation":"CREATE TABLE","operationParameters":{"isManaged":"true","description":null,"partitionBy":"[]","properties":"{\"delta.enableIcebergCompatV2\":\"true\",\"delta.universalFormat.enabledFormats\":\"iceberg\",\"delta.columnMapping.mode\":\"name\",\"delta.columnMapping.maxColumnId\":\"1\"}"},"isolationLevel":"Serializable","isBlindAppend":true,"operationMetrics":{},"engineInfo":"Apache-Spark/3.5.1 Delta-Lake/3.1.0","txnId":"a4d4593f-835c-4d00-81d8-27c1103343d2"}}
{"metaData":{"id":"a8477f73-f004-4a08-8397-3420d4df98a2","format":{"provider":"parquet","options":{}},"schemaString":"{\"type\":\"struct\",\"fields\":[{\"name\":\"c1\",\"type\":\"integer\",\"nullable\":true,\"metadata\":{\"delta.columnMapping.id\":1,\"delta.columnMapping.nested.ids\":{},\"delta.columnMapping.physicalName\":\"col-fdc375c2-e5f2-44c5-a5e9-2cdafca1ddfd\"}}]}","partitionColumns":[],"configuration":{"delta.enableIcebergCompatV2":"true","delta.universalFormat.enabledFormats":"iceberg","delta.columnMapping.mode":"name","delta.columnMapping.maxColumnId":"1"},"createdTime":1717753754108}}
{"protocol":{"minReaderVersion":2,"minWriterVersion":7,"writerFeatures":["columnMapping","icebergCompatV2"]}}

If you try to read this table you get the following error

_internal.DeltaProtocolError: Invalid JSON in file stats: data did not match any variant of untagged enum MetadataValue at line 1 column 147

Seems like what is causing this is that Delta adds "delta.columnMapping.nested.ids":{} to the metaData config, but the delta kernel doesn't support nested structs in meta data

What you expected to happen: I should be able to read a delta table written with uniform enabled

How to reproduce it:

1. create table with Uniform (and Iceberg) enabled

   CREATE TABLE uniform_table(c1 INT) USING DELTA TBLPROPERTIES(
   'delta.enableIcebergCompatV2' = 'true',
   'delta.universalFormat.enabledFormats' = 'iceberg');

2. Try to read table

   from deltalake import DeltaTable
   DeltaTable("uniform_table")

   More details:

[ion-elgreco]

Can you try it against at 0.18.0, if it still persist, then it deserves an upstream issue at delta-kernel-rs repo

[jeppe742]

@ion-elgreco It's also an issue with 0.18.0. Will try to create an issue in the delta-kernel-rs repo 😃

[jeppe742]

Hey @ion-elgreco Just fyi, the bug in delta-kernel-rs has finally been fixed and released in 0.2.0. Would it be possible to bump the dependency to get the fix?

[ion-elgreco]

Hey @ion-elgreco Just fyi, the bug in delta-kernel-rs has finally been fixed and released in 0.2.0. Would it be possible to bump the dependency to get the fix?

Feel free to open a PR to bump it, then I'll approve