Use CTE instead of temporary table in get_collection_stats

Creation of temporary tables are not allow in read-only db instances.
We support the use of read-only db instances

datalad_registry/blueprints/api/dataset_urls/tools.py

@@ -218,23 +218,19 @@ def get_collection_stats(select_stmt: Select) -> CollectionStats:
     Note: The execution of this function requires the Flask app's context
     """
 
-    # Cache the result of the select statement to a temporary table
-    tmp_tb = cache_result_to_tmp_tb(select_stmt, "tmp_tb")
+    base_cte = select_stmt.cte("base_cte")
 
-    # base_q = select_stmt.subquery("base_q")
-    base_q = select(tmp_tb).subquery("base_q")
-
-    datalad_ds_stats = get_dl_ds_collection_stats(base_q)
+    datalad_ds_stats = get_dl_ds_collection_stats(base_cte)
 
     # Total number of datasets, as individual repos, without any deduplication
     ds_count = db.session.execute(
-        select(func.count().label("ds_count")).select_from(base_q)
+        select(func.count().label("ds_count")).select_from(base_cte)
     ).scalar_one()
 
     return CollectionStats(
         datalad_ds_stats=datalad_ds_stats,
-        pure_annex_ds_stats=get_pure_annex_ds_collection_stats(base_q),
-        non_annex_ds_stats=get_non_annex_ds_collection_stats(base_q),
+        pure_annex_ds_stats=get_pure_annex_ds_collection_stats(base_cte),
+        non_annex_ds_stats=get_non_annex_ds_collection_stats(base_cte),
         summary=StatsSummary(
             unique_ds_count=datalad_ds_stats.unique_ds_stats.ds_count, ds_count=ds_count
         ),