PostgreSQL數據中`pg_logical`目錄的用途是什麼？

Question

我剛剛測試了我設置的PostgreSQL 9.4集羣的故障轉移時偶然發現了這個錯誤。在這裏，我想推動的奴隸，成爲新的主：

$ repmgr -f /etc/repmgr/repmgr.conf --verbose standby promote 

2014-09-22 10:46:37 UTC LOG: database system shutdown was interrupted; last known up at 2014-09-22 10:44:02 UTC 
2014-09-22 10:46:37 UTC LOG: database system was not properly shut down; automatic recovery in progress 
2014-09-22 10:46:37 UTC LOG: redo starts at 0/18000028 
2014-09-22 10:46:37 UTC LOG: consistent recovery state reached at 0/19000600 
2014-09-22 10:46:37 UTC LOG: record with zero length at 0/1A000090 
2014-09-22 10:46:37 UTC LOG: redo done at 0/1A000028 
2014-09-22 10:46:37 UTC LOG: last completed transaction was at log time 2014-09-22 10:36:22.679806+00 
2014-09-22 10:46:37 UTC FATAL: could not open directory "pg_logical/snapshots": No such file or directory 
2014-09-22 10:46:37 UTC LOG: startup process (PID 2595) exited with exit code 1 
2014-09-22 10:46:37 UTC LOG: aborting startup due to startup process failure 

pg_logical/snapshots DIR其實主節點上存在，它是空的。

UPD：我剛剛手動創建了空目錄pg_logical/snapshots和pg_logical/mappings，服務器已經開始沒有抱怨。 repmgr standby clone在同步時似乎忽略此目錄。但問題仍然存在，因爲我只是好奇這個目錄是什麼，也許我錯過了我的設置。只是谷歌搜索它沒有產生任何有意義的結果。

Answer 1

這是爲new logical changeset extraction/logical replication feature in 9.4。

這不應該發生，但是......它暗示了一個重要的錯誤，可能是repmgr。我會等待細節（repmgr版本等）。

更新：確認，it's a repmgr bug。它已經在git master中解決了（並且在此報告之前），並將在下一個版本中發佈。考慮到這個問題的重要性，哪一個最好不久。