spring-projects/spring-ai · error · RuntimeException

Drop Index failed!

Error message

Drop Index failed!

What it means

dropCollection then drops the index on the collection and throws a plain RuntimeException("Drop Index failed!") if the dropIndex RPC returns an exception. The index removal on the Milvus server failed, blocking the subsequent dropCollection step.

Source

Thrown at vector-stores/spring-ai-milvus-store/src/main/java/org/springframework/ai/vectorstore/milvus/MilvusVectorStore.java:607

		}
		return OPENAI_EMBEDDING_DIMENSION_SIZE;
	}

	// used by the test as well
	void dropCollection() {

		R<RpcStatus> status = this.milvusClient
			.releaseCollection(ReleaseCollectionParam.newBuilder().withCollectionName(this.collectionName).build());

		if (status.getException() != null) {
			throw new RuntimeException("Release collection failed!", status.getException());
		}

		status = this.milvusClient
			.dropIndex(DropIndexParam.newBuilder().withCollectionName(this.collectionName).build());

		if (status.getException() != null) {
			throw new RuntimeException("Drop Index failed!", status.getException());
		}

		status = this.milvusClient.dropCollection(DropCollectionParam.newBuilder()
			.withDatabaseName(this.databaseName)
			.withCollectionName(this.collectionName)
			.build());

		if (status.getException() != null) {
			throw new RuntimeException("Drop Collection failed!", status.getException());
		}
	}

	@Override
	public org.springframework.ai.vectorstore.observation.VectorStoreObservationContext.Builder createObservationContextBuilder(
			String operationName) {

		return VectorStoreObservationContext.builder(VectorStoreProvider.MILVUS.value(), operationName)
			.collectionName(this.collectionName)

View on GitHub (pinned to 98a7beda4f)

Solutions

1. Read the cause exception for the Milvus status code.
2. Ensure releaseCollection succeeded before dropIndex.
3. Handle/ignore 'index not found' cases and proceed to dropCollection.
4. Verify connectivity and permissions on the Milvus server.
5. Manually drop the index via Attu/CLI if the client state is stuck, then retry.

Example fix

// before
// dropIndex fails because collection was never released
// after
milvusClient.releaseCollection(ReleaseCollectionParam.newBuilder().withCollectionName(name).build());
milvusClient.dropIndex(DropIndexParam.newBuilder().withCollectionName(name).build());

// ensure the collection was released before dropping the index
// (releaseCollection must succeed first in the dropCollection flow)
milvusClient.releaseCollection(ReleaseCollectionParam.newBuilder().withCollectionName(collectionName).build());

try {
    // dropCollection flow invokes dropIndex internally
} catch (RuntimeException e) {
    String msg = e.getCause() != null ? e.getCause().getMessage() : e.getMessage();
    if (msg != null && msg.contains("index not found")) {
        // tolerate already-dropped index and continue
    } else {
        throw e;
    }
}

When it happens

Trigger: Called from shouldFilterWithCustomMetadataFieldName or dropCollection flow when milvusClient.dropIndex fails: index does not exist, collection still loaded, connection failure, or insufficient permissions.

Common situations: Index already dropped by a prior failed run; collection not released first (release step failed silently upstream); Milvus version requiring released state before index drop.

Related errors

• Drop Collection failed!
• Failed to create Index
• Release collection failed!
• Failed to invoke ensureIndex() method
• Failed to invoke createIndex() method

AI-assisted analysis of spring-projects/spring-ai@98a7beda4f (2026-09-11). Data as JSON: /api/errors/e7157dee85d3b64d. Report an issue: GitHub.