Remaining SQL compatibility issues from Compose stack evaluation (GH-289 backlog)

[coderabbitai]

Overview

Backlog items identified during the Compose stack evaluation in #289 that were not addressed by #294. Requested by @amotl.

Remaining items

@amotl, here's the concise status. After GH-294, the following items from this ticket appear still unaddressed (no patch, no open issue):

#	Issue	Notes
1	count(integer) is not a scalar function — HAVING count(?) = ? in registered model search	No patch in search_utils or elsewhere
2	ORDER BY CASE WHEN (creation_timestamp_ms IS NULL) THEN ? ELSE ? END — undefined return type on logged_models	No patch found
3	Updating a primary key is not supported — UPDATE experiment_tags SET experiment_id = ?	No patch found
4	link_prompts_to_trace not supported by tracking store	No patch found
5	Failed to send trace — MLFLOW_TRACKING_URI resolves to crate: instead of http://...	Likely a docs/setup issue

1. count(integer) is not a scalar function — HAVING count(?) = ? in registered model search

UnsupportedFeatureException[Function FunctionName{schema='null', name='count'}(integer) is not a scalar function.]

Triggered when searching registered models with tag-based filters (e.g. /ajax-api/2.0/mlflow/registered-models/search). The query uses HAVING count(?) = ? inside a subquery on registered_model_tags. No patch exists yet in mlflow_cratedb/patch/.

2. ORDER BY CASE WHEN ... END — invalid return type undefined on logged_models

UnsupportedFeatureException[Cannot ORDER BY 'CASE WHEN (creation_timestamp_ms IS NULL) THEN $3 ELSE $4 END': invalid return type 'undefined'.]

Triggered when visiting the models or runs page for an experiment. CrateDB cannot infer the return type of CASE WHEN (column IS NULL) THEN ? ELSE ? END when bound parameters are used. No patch exists yet.

3. Updating a primary key is not supported — UPDATE experiment_tags SET experiment_id = ?

Validation failed for experiment_id: Updating a primary key is not supported

CrateDB does not support updating primary key columns. The upstream MLflow code issues UPDATE experiment_tags SET experiment_id = ? WHERE .... No patch exists yet.

4. link_prompts_to_trace not supported by tracking store

Linking prompts to trace ... failed. Tracking store does not support `link_prompts_to_trace` method.

The link_prompts_to_trace method is not implemented in the mlflow-cratedb tracking store. No patch exists yet.

5. Failed to send trace — MLFLOW_TRACKING_URI resolves to crate: instead of http://...

When an mlflow-artifacts URI was supplied, the tracking URI must be a valid http or https URI, but it was currently set to crate:

Likely a Compose setup / documentation issue — the tracking URI for the demo experiment resolves to the crate: scheme rather than the HTTP server URI. Needs investigation.

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Backlog tracked from #289 after #294 was merged. Originally summarized by @coderabbitai.