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| author | Alvaro Herrera <alvherre@alvh.no-ip.org> | 2021-02-23 17:30:21 -0300 |
|---|---|---|
| committer | Alvaro Herrera <alvherre@alvh.no-ip.org> | 2021-02-23 17:30:21 -0300 |
| commit | 8deb6b38dc4c7a7fd4719ee45e4b00d62b27dffe (patch) | |
| tree | 5f3f90dd0620287eb900edd64cec34b5c0e0fbd4 /src/backend/access/heap/README.tuplock | |
| parent | 3db05e76f92846d4b54d7de251b0875cf1e23aa4 (diff) | |
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
Diffstat (limited to 'src/backend/access/heap/README.tuplock')
| -rw-r--r-- | src/backend/access/heap/README.tuplock | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/src/backend/access/heap/README.tuplock b/src/backend/access/heap/README.tuplock index d03ddf6cdcc..6441e8baf0e 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. |