Update description of spilled counters in pg_stat_replication_slots view.

This is to make the description of spilled counters clear.

Author: Amit Kapila
Reviewed-by: Sawada Masahiko
Discussion: https://postgr.es/m/CA+fd4k5_pPAYRTDrO2PbtTOe0eHQpBvuqmCr8ic39uTNmR49Eg@mail.gmail.com

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index f5cf163c8c68f57a52fa883b1a1ba49dbfdc594f..aeb694d4a86d76a062ed7915e827d2ecbafaeb11 100644 (file)
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -2603,9 +2603,9 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        
        
         Number of transactions spilled to disk after the memory used by
-        logical decoding exceeds logical_decoding_work_mem. The
-        counter gets incremented both for toplevel transactions and
-        subtransactions.
+        logical decoding of changes from WAL for this slot exceeds
+        logical_decoding_work_mem. The counter gets
+        incremented both for toplevel transactions and subtransactions.
       
      
 
@@ -2614,7 +2614,8 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         spill_count bigint
        
        
-        Number of times transactions were spilled to disk. Transactions
+        Number of times transactions were spilled to disk while performing
+        decoding of changes from WAL for this slot. Transactions
         may get spilled repeatedly, and this counter gets incremented on every
         such invocation.
       
@@ -2625,7 +2626,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         spill_bytes bigint
        
        
-        Amount of decoded transaction data spilled to disk.
+        Amount of decoded transaction data spilled to disk while performing
+        decoding of changes from WAL for this slot. This and other spill
+        counters can be used to gauge the I/O occurred during logical decoding
+        and accordingly can tune logical_decoding_work_mem.