feat(occurrences on eap): Implement run_stats_query in Occurrences EAP RPC class

[shashjar]

Precursor to #112889. First of two backend PRs to support attribute breakdowns for occurrences in Explore.

• Implements Occurrences.run_stats_query() for attribute distribution queries on occurrence trace items in EAP, following the same pattern as Spans.run_stats_query()
• Adds supporting infrastructure: occurrence attribute alias mappings, private attribute definitions, stats-excluded attributes
• Supports optional occurrence_category filtering (ERROR vs. ISSUE_PLATFORM)

[shashjar]

Note that arbitrary attributes on occurrence trace items are stored in EAP with columns constructed as f"attr[{key}]". This may require some transformation work down the line to make sure attributes get displayed nicely in the frontend.

[shashjar]

Note that (like the other query functions in the Occurrences RPC class) run_stats_query accepts an optional occurrence_category argument to filter down to error occurrences or issue platform occurrences (queries both by default). We may want to take this into account for Errors on Explore, i.e. if we want to limit the queries to error occurrences only.

Question for Explore team: will Errors on Explore be truly errors-only, or do we want to include issue platform events there as well?

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Unused constant defined but never referenced anywhere
  • Added filtering logic in run_stats_query to use OCCURRENCE_STATS_EXCLUDED_ATTRIBUTES_PUBLIC_ALIAS, preventing system-level identifiers from appearing in stats results.

Or push these changes by commenting:

@cursor push 91c2df869c

Preview (91c2df869c)

diff --git a/src/sentry/snuba/occurrences_rpc.py b/src/sentry/snuba/occurrences_rpc.py
--- a/src/sentry/snuba/occurrences_rpc.py
+++ b/src/sentry/snuba/occurrences_rpc.py
@@ -315,6 +315,9 @@
         response = snuba_rpc.trace_item_stats_rpc(stats_request)
         stats = []
 
+        from sentry.search.eap.occurrences.attributes import (
+            OCCURRENCE_STATS_EXCLUDED_ATTRIBUTES_PUBLIC_ALIAS,
+        )
         from sentry.search.eap.utils import can_expose_attribute, translate_internal_to_public_alias
 
         for result in response.results:
@@ -340,6 +343,8 @@
                                 SupportedTraceItemType.OCCURRENCES,
                             )
                             public_alias = public_alias or attribute.attribute_name
+                            if public_alias in OCCURRENCE_STATS_EXCLUDED_ATTRIBUTES_PUBLIC_ALIAS:
+                                continue
                             attrs[public_alias].append(
                                 {"label": bucket.label, "value": bucket.value}
                             )

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