12.14.4.3 Diagnostics During Index.xml Parsing

The MySQL server generates diagnostics when it finds problems while parsing the Index.xml file:

• Unknown tags are written to the error log. For example, the following message results if a collation definition contains a <aaa> tag:

  [Warning] Buffered warning: Unknown LDML tag:
  'charsets/charset/collation/rules/aaa'

• If collation initialization is not possible, the server reports an “Unknown collation” error, and also generates warnings explaining the problems, such as in the previous example. In other cases, when a collation description is generally correct but contains some unknown tags, the collation is initialized and is available for use. The unknown parts are ignored, but a warning is generated in the error log.

• Problems with collations generate warnings that clients can display with SHOW WARNINGS. Suppose that a reset rule contains an expansion longer than the maximum supported length of 6 characters:

  <reset>abcdefghi</reset>
  <i>x</i>

  An attempt to use the collation produces warnings:

  mysql> SELECT _utf8mb4'test' COLLATE utf8mb4_test_ci;
  ERROR 1273 (HY000): Unknown collation: 'utf8mb4_test_ci'
  mysql> SHOW WARNINGS;
  +---------+------+----------------------------------------+
  | Level   | Code | Message                                |
  +---------+------+----------------------------------------+
  | Error   | 1273 | Unknown collation: 'utf8mb4_test_ci'   |
  | Warning | 1273 | Expansion is too long at 'abcdefghi=x' |
  +---------+------+----------------------------------------+