docs: Explain why this panic might happen
@@ -645,6 +645,9 @@ impl Compactor {
let merged_schema = QueryableParquetChunk::merge_schemas(&query_chunks);
let sort_key = sort_key_from_catalog
+ // This can happen for data in catalogs created in "the before times"
+ // we do not currently plan to provide an upgrade path (instead we will wipe
+ // old catalogs)
.expect("Partition sort key should have been available in the catalog");
// Identify split time
