diff --git a/backend/entityservice/cache/helpers.py b/backend/entityservice/cache/helpers.py
index a3a05239..381fff3a 100644
--- a/backend/entityservice/cache/helpers.py
+++ b/backend/entityservice/cache/helpers.py
@@ -1,3 +1,16 @@
 def _get_run_hash_key(run_id):
     key = f'run:{run_id}'
     return key
+
+
+def _get_project_hash_key(project_id):
+    key = f'project:{project_id}'
+    return key
+
+
+def _convert_redis_result_to_int(res):
+    # redis returns bytes, and None if not present
+    if res is not None:
+        return int(res)
+    else:
+        return None
\ No newline at end of file
diff --git a/backend/entityservice/cache/progress.py b/backend/entityservice/cache/progress.py
index 10615be1..a18cab62 100644
--- a/backend/entityservice/cache/progress.py
+++ b/backend/entityservice/cache/progress.py
@@ -2,30 +2,45 @@
 
 from entityservice.settings import Config as globalconfig
 from entityservice.cache.connection import connect_to_redis
-from entityservice.cache.helpers import _get_run_hash_key
+from entityservice.cache.helpers import _get_run_hash_key, _get_project_hash_key, _convert_redis_result_to_int
+import entityservice.database as db
 
 logger = structlog.get_logger()
 
 
+def get_total_number_of_comparisons(project_id):
+    r = connect_to_redis(read_only=True)
+    key = _get_project_hash_key(project_id)
+    res = r.hget(key, 'total_comparisons')
+    # hget returns None if missing key/name, and bytes if present
+    if res:
+        return _convert_redis_result_to_int(res)
+    else:
+        # Calculate the number of comparisons
+        with db.DBConn() as conn:
+            total_comparisons = db.get_total_comparisons_for_project(conn, project_id)
+        # get a writable connection to redis
+        r = connect_to_redis()
+        res = r.hset(key, 'total_comparisons', total_comparisons)
+        r.expire(key, 60*60)
+        return total_comparisons
+
 def save_current_progress(comparisons, run_id, config=None):
     if config is None:
         config = globalconfig
     logger.debug(f"Updating progress. Compared {comparisons} CLKS", run_id=run_id)
-    r = connect_to_redis()
-    key = _get_run_hash_key(run_id)
-    r.hincrby(key, 'progress', comparisons)
-    r.expire(key, config.CACHE_EXPIRY)
+    if comparisons > 0:
+        r = connect_to_redis()
+        key = _get_run_hash_key(run_id)
+        r.hincrby(key, 'progress', comparisons)
+        r.expire(key, config.CACHE_EXPIRY)
 
 
 def get_progress(run_id):
     r = connect_to_redis(read_only=True)
     key = _get_run_hash_key(run_id)
     res = r.hget(key, 'progress')
-    # redis returns bytes, and None if not present
-    if res is not None:
-        return int(res)
-    else:
-        return None
+    return _convert_redis_result_to_int(res)
 
 
 def clear_progress(run_id):
diff --git a/backend/entityservice/database/selections.py b/backend/entityservice/database/selections.py
index 4ce1d35c..0d8d9120 100644
--- a/backend/entityservice/database/selections.py
+++ b/backend/entityservice/database/selections.py
@@ -229,27 +229,35 @@ def get_smaller_dataset_size_for_project(db, project_id):
 
 def get_total_comparisons_for_project(db, project_id):
     """
+    Returns the number of comparisons that a project requires.
+
+    For each block:
+        for each pairwise combination of data providers in each block:
+            multiply the block sizes together
+        then sum number of comparisons for each block
+    Sum the number of comparisons in all blocks together.
+
     :return total number of comparisons for this project
     """
-    expected_datasets = get_project_column(db, project_id, 'parties')
+
+    # The full computation is *hard* to do in postgres, so we return an array of sizes
+    # for each block and then use Python to find the pairwise combinations.
     sql_query = """
-        SELECT uploads.count as rows
-        from dataproviders, uploads
-        where
-          uploads.dp=dataproviders.id AND
-          dataproviders.project=%s
+        select block_name, array_agg(count) as counts
+        from blocks
+        where dp in (
+            select id from dataproviders where project = %s
+        )
+        group by block_name
         """
+
     query_results = query_db(db, sql_query, [project_id])
-    if len(query_results) < expected_datasets:
-        return 'NA'
-    elif len(query_results) == expected_datasets:
-        counts = (qr['rows'] for qr in query_results)
-        total_comparisons = sum(
-            c0 * c1 for c0, c1 in itertools.combinations(counts, 2))
-        return total_comparisons
-    else:
-        raise ValueError(f'expected at most {expected_datasets} '
-                         f'datasets, got {len(query_results)}')
+    total_comparisons = 0
+    for block in query_results:
+        num_comparisons_in_block = sum(c0 * c1 for c0, c1 in itertools.combinations(block['counts'], 2))
+        total_comparisons += num_comparisons_in_block
+
+    return total_comparisons
 
 
 def get_dataprovider_id(db, update_token):
diff --git a/backend/entityservice/tasks/comparing.py b/backend/entityservice/tasks/comparing.py
index fe463519..10af0312 100644
--- a/backend/entityservice/tasks/comparing.py
+++ b/backend/entityservice/tasks/comparing.py
@@ -262,6 +262,9 @@ def new_child_span(name, parent_scope=None):
     log.debug('Both chunks are fetched and deserialized')
     task_span.log_kv({'size1': chunk_dp1_size, 'size2': chunk_dp2_size, 'chunk_info': chunk_info})
 
+    assert chunk_dp1_size > 0, "Zero sized chunk in dp1"
+    assert chunk_dp2_size > 0, "Zero sized chunk in dp2"
+
     with new_child_span('comparing-encodings') as parent_scope:
 
         log.debug("Calculating filter similarity")
@@ -285,11 +288,12 @@ def reindex_using_encoding_ids(recordarray, encoding_id_list):
 
     log.debug('Encoding similarities calculated')
 
-    with new_child_span('update-comparison-progress'):
+    with new_child_span('update-comparison-progress') as scope:
         # Update the number of comparisons completed
         comparisons_computed = chunk_dp1_size * chunk_dp2_size
         save_current_progress(comparisons_computed, run_id)
-        log.info("Comparisons: {}, Links above threshold: {}".format(comparisons_computed, len(sims)))
+        scope.span.log_kv({'comparisons': comparisons_computed, 'num_similar': len(sims)})
+        log.debug("Comparisons: {}, Links above threshold: {}".format(comparisons_computed, len(sims)))
 
     with new_child_span('save-comparison-results-to-minio'):
         num_results = len(sims)
diff --git a/backend/entityservice/tasks/run.py b/backend/entityservice/tasks/run.py
index bff98ed3..c6c36e5c 100644
--- a/backend/entityservice/tasks/run.py
+++ b/backend/entityservice/tasks/run.py
@@ -45,7 +45,6 @@ def prerun_check(project_id, run_id, parent_span=None):
 
         log.debug("Updating redis cache for run")
         set_run_state_active(run_id)
-        progress_cache.save_current_progress(comparisons=0, run_id=run_id)
 
     create_comparison_jobs.apply_async(
         kwargs={'project_id': project_id, 'run_id': run_id, 'parent_span': prerun_check.get_serialized_span()},
diff --git a/backend/entityservice/views/run/status.py b/backend/entityservice/views/run/status.py
index ff5e50ea..beca1ebd 100644
--- a/backend/entityservice/views/run/status.py
+++ b/backend/entityservice/views/run/status.py
@@ -51,8 +51,8 @@ def get(project_id, run_id):
         # Computing similarity
         abs_val = progress_cache.get_progress(run_id)
         if abs_val is not None:
-            with db.DBConn() as conn:
-                max_val = db.get_total_comparisons_for_project(conn, project_id)
+            max_val = progress_cache.get_total_number_of_comparisons(project_id)
+            logger.debug(f"total comparisons: {max_val}")
     else:
         # Solving for mapping (no progress)
         abs_val = None