In /entries, don't collect entries into a list (keep it a generator).

For #269.

CHANGES.rst

@@ -12,6 +12,11 @@ Version 2.8
 Unreleased
 
 * In the web application, show maxrss when debug is enabled. (:issue:`269`)
+* In the web application, decrease memory usage of the entries page
+  when there are a lot of entries
+  (e.g. for 2.5k entries, the maxrss decreased from 115 MiB to 75 MiB),
+  at the expense of making "entries for feed" slightly slower.
+  (:issue:`269`)
 
 
 Version 2.7

src/reader/_app/__init__.py

@@ -119,6 +119,7 @@ def get_reader():
         g.reader = current_app.config['READER_CONFIG'].make_reader(
             'app', plugin_loader=current_app.plugin_loader
         )
+        # TODO: lowering g.reader._storage.chunk_size may reduce memory usage slightly
     return g.reader
 
 
@@ -308,11 +309,14 @@ def get_entry_counts(**kwargs):
         else:
             raise
 
-    entries = list(entries)
-
     entries_data = None
     if feed_url:
-        entries_data = [e.id for e in entries]
+        # TODO: duplicated from entries = ... above
+        # TODO: can be made faster with a get_entry_ids() method
+        entries_data = [
+            e.id
+            for e in get_entries(**kwargs, limit=request.args.get('limit', type=int))
+        ]
 
     feed_entry_counts = None
     if feed_url:

src/reader/_app/templates/entries.html

@@ -243,8 +243,9 @@
 {% endif %}
 
 
-
+{% set vars = namespace(entry_index=0) %}
 {% for entry in entries %}
+{% set vars.entry_index = loop.index %}
 
 {% set feed = entry.feed %}
 {% set content, _ = entry_content(entry, prefer_summary=False) %}
@@ -360,15 +361,15 @@ <h2><a href="{{ entry.link }}">
 
 
 {% set limit = request.args.get('limit') | int %}
-{% if limit -%}
+{% if limit and vars.entry_index >= limit -%}
 {%- set args = request.args.copy() -%}
 {%- set _ = args.poplist('limit') -%}
 
 <p>
-showing only the first {{ limit }} entries;
+showing only the first {{ vars.entry_index }} entries;
 <a href='
     {{- url_for('.entries', **args) -}}
-    {%- if entries %}#entry-{{ entries | length }}{% endif -%}
+    {%- if entries %}#entry-{{ vars.entry_index }}{% endif -%}
 '>show all entries</a>
 </p>