GROUP_CONCAT Configuration
Applies to ✅ Open Source Edition ✅ Express Edition ✅ Professional Edition ✅ Enterprise Edition
The MySQL GROUP_CONCAT function suffers from a controversial design decision where results are truncated after a certain length, the @@group_concat_max_len.
Whenever jOOQ generates a GROUP_CONCAT function, by default, that MySQL system variable is increased to the maximum value for the scope of a single statement, e.g.
SET @T = @@GROUP_CONCAT_MAX_LEN; SET @@GROUP_CONCAT_MAX_LEN = 4294967295; SELECT GROUP_CONCAT(TITLE SEPARATOR ', ') FROM BOOK; SET @@GROUP_CONCAT_MAX_LEN = @T;
More details here. While this is a reasonable default behaviour (as opposed to the random truncation), it may occasionally be undesired, e.g. if statement batches (; separated statements) aren't possible in a single JDBC statement. The feature can be turned off with
Example configuration
Settings settings = new Settings()
.withRenderGroupConcatMaxLenSessionVariable(false); // Defaults to true
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