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  1. MariaDB Server
  2. MDEV-32898

Phantom rows caused by UPDATE of PRIMARY KEY

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    Description

      Under REPEATABLE-READ isolation level，an UPDATE statement which update the value of primary key caused phantom rows in another transaction.
      How to repeat:

      /* init */ CREATE TABLE t(a INT PRIMARY KEY, b INT);
      		 
      /* init */ INSERT INTO t VALUES (1, 1);
      		 
      /* init */ INSERT INTO t VALUES (2, 2);
      		 
      /* t1 */ SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
      		 
      /* t2 */ SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
      		 
       
      		 
      /* t1 */ BEGIN;
      		 
      /* t1 */ SELECT * FROM t LOCK IN SHARE MODE;
      		 
      /* t2 */ BEGIN;
      		 
      /* t2 */ SELECT * FROM t;  -- [(1, 1), (2, 2)]
      		 
      /* t1 */ UPDATE t SET a=3 WHERE b = 2;
      		 
      /* t1 */ COMMIT;
      		 
      /* t2 */ UPDATE t SET b=3;
      		 
      /* t2 */ SELECT * FROM t; -- [(1, 3), (2, 2), (3, 3)] 
      /* t2 */ COMMIT;

      It appears that a phantom row (2, 2) showed up in the second consistent read of T2. And if you commit the second transaction, the phantom row will disappear. I'm not sure whether this is a new bug or a duplicate one. From the user's perspective, I haven't inserted a new row, updating existing rows should not result in phantom rows.

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          blocks

          Bug - A problem which impairs or prevents the functions of the product. MDEV-33802 Weird read view after ROLLBACK of other transactions.

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed
          relates to

          Task - A task that needs to be done. MDEV-33762 Document innodb_snapshot_isolation

          • Major - Major loss of function.
          • Open

          Bug - A problem which impairs or prevents the functions of the product. MDEV-14589 InnoDB should not lock a delete-marked record

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-26642 Weird SELECT view when a record is modified to the same value by two transactions

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-26643 Inconsistent behaviors of UPDATE under RU & RC isolation level

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Task - A task that needs to be done. MDEV-33455 skip modified rows in parallel XA replication, don't wait

          • Critical - Crashes, loss of data, severe memory leak.
          • Open

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              axel Axel Schwenke
              zhuangliu Zhuang Liu
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              Dates

                Created:
                Updated:
                Resolved:

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