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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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          Epic - Created by Jira Software - do not edit or delete. Issue type for a big user story that needs to be broken down. MDEV-4912 Data type plugin API version 1

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-13530 VARBINARY doesn't convert to to BLOB for sizes 65533, 65534 and 65535

          • Major - Major loss of function.
          • Closed

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              bar Alexander Barkov
              bar Alexander Barkov
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                Created:
                Updated:
                Resolved:

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