postgres.git / summary / log / commit / refs

commit    2583917075ae9fc40d29c679867367db68be004b
Author:   Alvaro Herrera <alvherre@alvh.no-ip.org>
Date:     Tue Feb 23 20:30:21 2021 +0000
First released in: 14.0, 9.6.22, 10.17, 11.12, 12.7, 13.3

    Reinstate HEAP_XMAX_LOCK_ONLY|HEAP_KEYS_UPDATED as allowed
    
    Commit 866e24d47db1 added an assert that HEAP_XMAX_LOCK_ONLY and
    HEAP_KEYS_UPDATED cannot appear together, on the faulty assumption that
    the latter necessarily referred to an update and not a tuple lock; but
    that's wrong, because SELECT FOR UPDATE can use precisely that
    combination, as evidenced by the amcheck test case added here.
    
    Remove the Assert(), and also patch amcheck's verify_heapam.c to not
    complain if the combination is found.  Also, out of overabundance of
    caution, update (across all branches) README.tuplock to be more explicit
    about this.
    
    Author: Julien Rouhaud <rjuju123@gmail.com>
    Reviewed-by: Mahendra Singh Thalor <mahi6run@gmail.com>
    Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
    Discussion: https://postgr.es/m/20210124061758.GA11756@nol


 src/backend/access/heap/README.tuplock | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/heap/README.tuplock b/src/backend/access/heap/README.tuplock
index 9674d0c0f07..dbd446a0d09 100644
--- a/src/backend/access/heap/README.tuplock
+++ b/src/backend/access/heap/README.tuplock
@@ -146,9 +146,10 @@ The following infomask bits are applicable:
   FOR UPDATE; this is implemented by the HEAP_KEYS_UPDATED bit.
 
 - HEAP_KEYS_UPDATED
-  This bit lives in t_infomask2.  If set, indicates that the XMAX updated
-  this tuple and changed the key values, or it deleted the tuple.
-  It's set regardless of whether the XMAX is a TransactionId or a MultiXactId.
+  This bit lives in t_infomask2.  If set, indicates that the operation(s) done
+  by the XMAX compromise the tuple key, such as a SELECT FOR UPDATE, an UPDATE
+  that modifies the columns of the key, or a DELETE.  It's set regardless of
+  whether the XMAX is a TransactionId or a MultiXactId.
 
 We currently never set the HEAP_XMAX_COMMITTED when the HEAP_XMAX_IS_MULTI bit
 is set.


[parent: 6e6fecf49538]