Fixed error only returning a page of results (#921)

The root cause: async_execute only materialises the first result
page (by design — it says so in its docstring). The streaming query
set fetch_size=20 and expected to iterate all results, but only got
the first 20 rows back.

The fix uses
  asyncio.to_thread(lambda: list(tg.session.execute(...)))
which lets the sync driver iterate
all pages in a worker thread — exactly what the pre-async code did.

trustgraph-flow/trustgraph/query/triples/cassandra/service.py

@@ -17,7 +17,6 @@ from .... schema import TriplesQueryRequest, TriplesQueryResponse, Error
 from .... schema import Term, Triple, IRI, LITERAL, TRIPLE, BLANK
 from .... base import TriplesQueryService
 from .... base.cassandra_config import add_cassandra_args, resolve_cassandra_config
-from .... tables.cassandra_async import async_execute
 
 # Module logger
 logger = logging.getLogger(__name__)
@@ -348,7 +347,12 @@ class Processor(TriplesQueryService):
                 cql = f"SELECT d, s, p, o, otype, dtype, lang FROM {tg.collection_table} WHERE collection = %s"
                 params = [query.collection]
                 statement = SimpleStatement(cql, fetch_size=batch_size)
-                result_set = await async_execute(tg.session, statement, params)
+                # async_execute only materialises the first page;
+                # this query needs all pages, so use sync execute
+                # in a worker thread where page iteration can block.
+                result_set = await asyncio.to_thread(
+                    lambda: list(tg.session.execute(statement, params))
+                )
 
             else:
                 async for batch, is_final in self._fallback_stream(workspace, query, batch_size):