Avoiding PostgreSQL deadlocks when performing bulk update and delete operations

Question

We have a single table which does not have references to any other tables.

┬────────────┬─────────────┬───────────────┬───────────────╮
│id_A(bigint)│id_B(b         


        

Answer 1

Use explicit row-level locking in ordered subqueries in all competing queries. (Simple SELECT does not compete.)

DELETE

DELETE FROM table_name t
USING (
   SELECT id_A, id_B
   FROM   table_name 
   WHERE  id_A = ANY(array_of_id_A)
   AND    id_B = ANY(array_of_id_B)
   ORDER  BY id_A, id_B
   FOR    UPDATE
   ) del
WHERE  t.id_A = del.id_A
AND    t.id_B = del.id_B;

UPDATE

UPDATE table_name t
SET    val_1 = 'some value'
     , val_2 = 'some value'
FROM (
   SELECT id_A, id_B
   FROM   table_name 
   WHERE  id_A = ANY(array_of_id_A)
   AND    id_B = ANY(array_of_id_B)
   ORDER  BY id_A, id_B
   FOR    NO KEY UPDATE  -- Postgres 9.3+
-- FOR    UPDATE         -- for older versions or updates on key columns
   ) upd
WHERE  t.id_A = upd.id_A
AND    t.id_B = upd.id_B;

This way, rows are locked in consistent order as advised in the manual.

Assuming that id_A, id_B are never updated, even rare corner case complications like detailed in the "Caution" box in the manual are not possible.

While not updating key columns, you can use the weaker lock mode FOR NO KEY UPDATE. Requires Postgres 9.3 or later.

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The other (slow and sure) option is to use the Serializable Isolation Level for competing transactions. You would have to prepare for serialization failures, in which case you have to retry the command.