Limitations

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Because ClickHouse is a columnar OLAP store (not a transactional RDBMS), some Ash features are intentionally unsupported. The data layer reports these via can?/2 so Ash can fail fast or fall back appropriately.

Not supported

FeatureWhy
:transactClickHouse has no multi-statement transactions
:lockLocking is a no-op (and reported unsupported)
:keysetClickHouse has no token-based keyset pagination — use offset/limit
:upsertClickHouse has no ON CONFLICT — use create + update_query
:joinJOINs are not yet implemented
:combine (UNION/INTERSECT)Not yet implemented (Ash can do it in memory)
:filter_relationshipNot yet implemented
{:exists, :unrelated}Not yet implemented
{:aggregate_relationship, _}Not yet implemented
:expression_calculation_sortNot supported
:aggregate_filter / :aggregate_sortNot supported
:update_manyUse :update_query instead
:composite_type / :through_relationshipNot supported
:bulk_create_with_partial_successNot supported
:bulk_upsert_return_skippedNot supported
{:query_aggregate, :list | :first | :exists | :custom}Only count/sum/avg/min/max
{:atomic, _}Not supported

Supported

  • CRUD (create, read, update, destroy)
  • filter, sort, limit, offset, select, distinct
  • bulk_create (batched INSERT)
  • update_query / destroy_query (ALTER TABLE ... UPDATE/DELETE)
  • Native aggregates count, sum, avg, min, max
  • multitenancy (database- or attribute-based)
  • calculate, composite_primary_key, nested_expressions, boolean_filter
  • stream, changeset_filter, action_select, expression_calculation
  • async_engine

Workarounds

  • Upsert: Ash.create/2 then Ash.update_query!/3 (or ALTER TABLE ... UPDATE).
  • Transactions: batch work in a single mutation/insert; accept eventual consistency for ALTER mutations (control with mutations_sync).
  • Pagination: use offset/limit instead of keyset.
  • Joins / relationships: not yet available — model denormalized tables or resolve relationships in your domain code for now.

Errors

Failures from the ClickHouse client are wrapped in AshClickhouse.Error.ClickhouseError, which carries :message, :query, :params, and :reason. This keeps Ash error presentation consistent.