[BUG] [Azure AI Search - Indexers failing when connected to CosmosDB with Hierarchical Partition Keys]

[danielmacedo90]

API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/main/specification/search/data-plane/Azure.Search/preview/2025-05-01-preview/examples/SearchServiceCreateIndexer.json

API Spec version

2025-05-01-preview

Describe the bug

I have an Azure Search Service configured with CosmosDB as the data source. My CosmosDB collections use hierarchical partition keys.

DataSources, Indexes, and Indexers were correctly created and everything was working fine until April 11th, 2025.

After that date, without any configuration change in either the Search service or CosmosDB, all Indexer executions started failing.

The error shown is:

This subpartitioned container has more than 1 partition key path please use "PartitionKeyPaths"

Previously, the Indexer worked without requiring explicit configuration for multiple partition key paths.

Expected behavior

The Indexer should continue working without manual specification of PartitionKeyPaths, just as it worked before April 11th, 2025.

Actual behavior

Indexer executions fail systematically with the error:

This subpartitioned container has more than 1 partition key path please use "PartitionKeyPaths"

No changes were made to my CosmosDB collections or Search service configurations before or after the issue started happening.

Reproduction Steps

1. Create a CosmosDB container with hierarchical partition keys.
2. Create a Data Source in Azure Search Service pointing to this CosmosDB container.
3. Define an Index and an Indexer associated with the Data Source.
4. Run the Indexer and it will fail. (note that before 2025-04-11 it ran successfully).

Environment

No response