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| author | Alexander Korotkov | 2023-03-22 21:13:37 +0000 |
|---|---|---|
| committer | Alexander Korotkov | 2023-03-22 21:26:59 +0000 |
| commit | 11470f544e3729c60fab890145b2e839cbc8905e (patch) | |
| tree | 8ebd3c5b4aab9023e54e71e892b91a5beb9de8dc /src/backend/access/table/tableam.c | |
| parent | 764da7710bf68eebb2c0facb2f871bc3c7a705b6 (diff) | |
Allow locking updated tuples in tuple_update() and tuple_delete()
Currently, in read committed transaction isolation mode (default), we have the
following sequence of actions when tuple_update()/tuple_delete() finds
the tuple updated by concurrent transaction.
1. Attempt to update/delete tuple with tuple_update()/tuple_delete(), which
returns TM_Updated.
2. Lock tuple with tuple_lock().
3. Re-evaluate plan qual (recheck if we still need to update/delete and
calculate the new tuple for update).
4. Second attempt to update/delete tuple with tuple_update()/tuple_delete().
This attempt should be successful, since the tuple was previously locked.
This patch eliminates step 2 by taking the lock during first
tuple_update()/tuple_delete() call. Heap table access method saves some
efforts by checking the updated tuple once instead of twice. Future
undo-based table access methods, which will start from the latest row version,
can immediately place a lock there.
The code in nodeModifyTable.c is simplified by removing the nested switch/case.
Discussion: https://postgr.es/m/CAPpHfdua-YFw3XTprfutzGp28xXLigFtzNbuFY8yPhqeq6X5kg%40mail.gmail.com
Reviewed-by: Aleksander Alekseev, Pavel Borisov, Vignesh C, Mason Sharp
Reviewed-by: Andres Freund, Chris Travers
Diffstat (limited to 'src/backend/access/table/tableam.c')
| -rw-r--r-- | src/backend/access/table/tableam.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/src/backend/access/table/tableam.c b/src/backend/access/table/tableam.c index a5e6c92f35e..2a1a6ced3c7 100644 --- a/src/backend/access/table/tableam.c +++ b/src/backend/access/table/tableam.c @@ -306,7 +306,8 @@ simple_table_tuple_delete(Relation rel, ItemPointer tid, Snapshot snapshot) GetCurrentCommandId(true), snapshot, InvalidSnapshot, true /* wait for commit */ , - &tmfd, false /* changingPart */ ); + &tmfd, false /* changingPart */ , + NULL); switch (result) { @@ -355,7 +356,8 @@ simple_table_tuple_update(Relation rel, ItemPointer otid, GetCurrentCommandId(true), snapshot, InvalidSnapshot, true /* wait for commit */ , - &tmfd, &lockmode, update_indexes); + &tmfd, &lockmode, update_indexes, + NULL); switch (result) { |