Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Not a Bug
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10.0.38, 5.5.64, 10.4.10
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None
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CentOS Linux 7.5.1804 (Core) (VPS Plesk environment), PHP 7.2.25
Description
Changing the collation of a LONGTEXT column (using ALTER TABLE ... CHANGE) truncates the data contained in it to exactly 65535 characters long (the max length of a TEXT type column?).
I've confirmed/reproduced this with MariaDB 5.5.64 and 10.0.38. MySQL 5.6.13 doesn't experience this behaviour.
The problematic query is in the form of:
ALTER TABLE <table_name> CHANGE <column_name> <column_name> LONGTEXT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NOT NULL
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The following work fine/as expected:
ALTER TABLE <table_name> MODIFY <column_name> LONGTEXT CHARACTER SET utf8mb4
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and:
ALTER TABLE <table_name> CONVERT TO CHARACTER SET utf8mb4
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(The specific collation or the type of data contained in the LONGTEXT column doesn't seem to matter; I'm able to reproduce it every time. Also both InnoDB and MyISAM storage engines experience the same behaviour.)
Side notes
I originally posted this issue on PhpMyAdmin's github page and got directed here: https://github.com/phpmyadmin/phpmyadmin/issues/15670
I hope I've included enough information.