Feature

• Update latest items in real-time on the server node (#342).
• Update categorized popular items in real-time on the server node (#343).

Performance

• Optimize copier by skipping equal maps and reusing slice space (#337).
• Add data skipping indices for ClickHouse (#349).
• Limit the number feedback used in fallback item-based similarity recommendation (#350).

Fix

• Fix concurrent map read in configuration (#338 authorized by @winwill2012, #347).
• Fix worker failure when there is no feedback (#340).
• Fix inefficient implementation of hidden items (#341).

Upgrade Guide

• Configuration: A new option has been added to limit the number feedback used in fallback item-based similarity recommendation. Larger value means more accurate recommendation but spend more time.

# The number of feedback used in fallback item-based similar recommendation. The default values is 10.
num_feedback_fallback_item_based = 20

• ClickHouse: Add indices manually if using ClickHouse as data storage.

ALTER TABLE feedback ADD INDEX user_index user_id TYPE bloom_filter(0.01) GRANULARITY 1;
ALTER TABLE feedback ADD INDEX item_index item_id TYPE bloom_filter(0.01) GRANULARITY 1;

• Redis: Remove incompatible stale cache.

redis-cli KEYS "popular_items*" | xargs redis-cli DEL
redis-cli KEYS "latest_items*" | xargs redis-cli DEL