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  1. MariaDB Server
  2. MDEV-9319

ALTER from a bigger to a smaller blob type truncates too much data

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      Description

      DROP TABLE IF EXISTS t1;
      CREATE TABLE t1 (a BLOB) ENGINE=MyISAM;
      INSERT INTO t1 VALUES (REPEAT(0x61,65000));
      SELECT LENGTH(a) FROM t1;
      ALTER TABLE t1 MODIFY a TINYBLOB;
      SELECT LENGTH(a) FROM t1;

      returns 65000 before ALTER:

      +-----------+
      | LENGTH(a) |
      +-----------+
      |     65000 |
      +-----------+

      and returns 232 after ALTER:

      +-----------+
      | LENGTH(a) |
      +-----------+
      |       232 |
      +-----------+

      This looks wrong. The expected length after ALTER is 255.

      It also does not produce any warnings on truncation. Probably it should.

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              • Assignee:
                bar Alexander Barkov
                Reporter:
                bar Alexander Barkov
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                • Created:
                  Updated:
                  Resolved: