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  1. MariaDB Server
  2. MDEV-32727

No warning and misleading error message for PARTITION BY KEY with index prefixes

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    Description

      Columns index prefixes are not supported by key partitioning. However, there is no warning, and a misleading error message:

      CREATE OR REPLACE TABLE t1 (
          a VARCHAR(10),
          b VARCHAR(10),
          c VARCHAR(10),
          PRIMARY KEY (a(5), b, c(5))
      ) PARTITION BY KEY() PARTITIONS 2;
      

      a(5) and c(5) are silently ignored, so the effect is the same as the following, but no warnings are given:

      CREATE OR REPLACE TABLE t1 (
          a VARCHAR(10),
          b VARCHAR(10),
          c VARCHAR(10),
          PRIMARY KEY (b)
      ) PARTITION BY KEY() PARTITIONS 2;
      

      If all specified columns in the primary key have index prefixes, a misleading error message is returned:

      CREATE OR REPLACE TABLE t1 (
          a VARCHAR(10),
          b VARCHAR(10),
          c VARCHAR(10),
          PRIMARY KEY (a(5), b(5), c(5))
      ) PARTITION BY KEY() PARTITIONS 2;
      ERROR 1503 (HY000): A PRIMARY KEY must include all columns in the table's partitioning function
      

      This issue was fixed in MySQL 8.0.21:

      CREATE TABLE t1 (
          a VARCHAR(10),
          b VARCHAR(10),
          c VARCHAR(10),
          PRIMARY KEY (b)
      ) PARTITION BY KEY() PARTITIONS 2;
       
      SHOW WARNINGS;
      +---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
      | Level   | Code | Message                                                                                                                                                                                                    |
      +---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
      | Warning | 1681 | Column 'test.t1.a' having prefix key part 'a(10)' is ignored by the partitioning function. Use of prefixed columns in the PARTITION BY KEY() clause is deprecated and will be removed in a future release. |
      | Warning | 1681 | Column 'test.t1.c' having prefix key part 'c(2)' is ignored by the partitioning function. Use of prefixed columns in the PARTITION BY KEY() clause is deprecated and will be removed in a future release.  |
      +---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
      

      and

      CREATE TABLE t1 (
          a VARCHAR(10),
          b VARCHAR(10),
          c VARCHAR(10),
          PRIMARY KEY (a(5), b(5), c(5))
      ) PARTITION BY KEY() PARTITIONS 2;
      ERROR 1503 (HY000): A PRIMARY KEY must include all columns in the table's partitioning function (prefixed columns are not considered).
      

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              ycp Yuchen Pei
              greenman Ian Gilfillan
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                Updated:

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