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:Press CTRL+C to copy[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:Press CTRL+C to copy<reset>abcdefghi</reset> <i>x</i>
An attempt to use the collation produces warnings:
Press CTRL+C to copymysql> 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' | +---------+------+----------------------------------------+