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Dmitry Shulga authored
The problem was that server didn't check resulting size of prepared statement argument which was set using mysql_send_long_data() API. By calling mysql_send_long_data() several times it was possible to create overly big string and thus force server to allocate memory for it. There was no way to limit this allocation. The solution is to add check for size of result string against value of max_long_data_size start-up parameter. When intermediate string exceeds max_long_data_size value an appropriate error message is emitted. We can't use existing max_allowed_packet parameter for this purpose since its value is limited by 1GB and therefore using it as a limit for data set through mysql_send_long_data() API would have been an incompatible change. Newly introduced max_long_data_size parameter gets value from max_allowed_packet parameter unless its value is specified explicitly. This new parameter is marked as deprecated and will be eventually replaced by max_allowed_packet parameter. Value of max_long_data_size parameter can be set only at server startup.
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