docs: Update HOT update docs for 19d8e2308b

Commit 19d8e2308b changed when the HOT update optimization is possible
but neglected to update the Heap-Only Tuples (HOT) documentation.  This
patch updates that documentation accordingly.

Author: Elizabeth Christensen
Backpatch-through: 16
Reviewed-By: Stephen Frost, Alvaro Herrera
Discussion: https://postgr.es/m/CABoUFXRjisr58Ct_3VsFEdQx+fJeQTWTdJnM7XAp=8MUbtoa9A@mail.gmail.com

diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 3ea4e5526df5a054360345dc08ba4ee0072aaaab..aabb1d5c09180bbc52d0528942868ddf60f5a492 100644 (file)
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -1097,8 +1097,10 @@ data. Empty in ordinary tables.
   
    
     
-     The update does not modify any columns referenced by the table's
-     indexes, including expression and partial indexes.
+     The update does not modify any columns referenced by the table's indexes,
+     not including summarizing indexes.  The only summarizing index method in
+     the core PostgreSQL distribution is 
+     linkend="brin">BRIN.
      
    
    
@@ -1114,7 +1116,8 @@ data. Empty in ordinary tables.
   
    
     
-     New index entries are not needed to represent updated rows.
+     New index entries are not needed to represent updated rows, however,
+     summary indexes may still need to be updated.
     
    
    
@@ -1130,14 +1133,12 @@ data. Empty in ordinary tables.
  
 
  
-  In summary, heap-only tuple updates can only be created
-  if columns used by indexes are not updated.  You can
-  increase the likelihood of sufficient page space for
+  You can increase the likelihood of sufficient page space for
   HOT updates by decreasing a table's 
-  linkend="reloption-fillfactor">fillfactor.
-  If you don't, HOT updates will still happen because
-  new rows will naturally migrate to new pages and existing pages with
-  sufficient free space for new row versions.  The system view 
+  linkend="reloption-fillfactor">fillfactor.  If you
+  don't, HOT updates will still happen because new rows
+  will naturally migrate to new pages and existing pages with sufficient free
+  space for new row versions.  The system view 
   linkend="monitoring-pg-stat-all-tables-view">pg_stat_all_tables
   allows monitoring of the occurrence of HOT and non-HOT updates.
  




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