Mysql default table name length is 30 characters.

Phpbb installation prompts user to choose their own table prefix. If chosen table prefix is longer that 6 characters (for example, 'phpbb3_'), then at least one of the table names ('phpbb3_search_wordmatch_un_mtch') becomes longer than 30 characters and installation stops with a general error:

[code]
General Error
Index name 'phpbb3_search_wordmatch_un_mtch' on table 'phpbb3_search_wordmatch' is too long. The maximum is 30 characters.

BACKTRACE

FILE: (not given by php)
LINE: (not given by php)
CALL: msg_handler()

FILE: [ROOT]/phpbb/db/tools.php
LINE: 2124
CALL: trigger_error()

FILE: [ROOT]/phpbb/db/tools.php
LINE: 664
CALL: phpbb\db\tools->sql_create_unique_index()

FILE: [ROOT]/install/install_install.php
LINE: 1216
CALL: phpbb\db\tools->sql_create_table()

FILE: [ROOT]/install/install_install.php
LINE: 99
CALL: install_install->load_schema()

FILE: [ROOT]/install/index.php
LINE: 409
CALL: install_install->main()

FILE: [ROOT]/install/index.php
LINE: 289
CALL: module->load()
[/code]

At very least phpbb should provide a warning about mysql max table name length and, accordingly, desired prefix length.

Ideally, phpbb should check the max name length and not start DB/table creation while prefix is too long.