Fix issue #4841 #4842
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Fix issue #4841 #4842
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Incorrectly attempt to use a collation with id larger than 255 during backend handshake Problem: When creating a backend connection, if the frontend connection has configured a collation with id larger than 255 (for example using SET NAMES utf8mb4 COLLATE utf8mb4_0900_as_ci; , ProxySQL may try to create a new connection using such collation. The problem is that at protocol level, during handshake only 1 byte can be used to configure the collation. That means that if ProxySQL sets a collation greater than 255 , only the less significant byte is used. Therefore even if ProxySQL believes that the backend connection will use the specified collation, mysql_real_connect() is using a different collation. For example, using collation 305 will lead to use collation 49 (305-256). Solution: When a collation id greater than 255 is detected, the default collation for that character set is used. ProxySQL will later issue a SET NAMES ... COLLATE to address the mismatch.
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Incorrectly attempt to use a collation with id larger than 255 during backend handshake
Problem:
When creating a backend connection, if the frontend connection has configured a collation with id larger than 255 (for example using SET NAMES utf8mb4 COLLATE utf8mb4_0900_as_ci; , ProxySQL may try to create a new connection using such collation. The problem is that at protocol level, during handshake only 1 byte can be used to configure the collation. That means that if ProxySQL sets a collation greater than 255 , only the less significant byte is used. Therefore even if ProxySQL believes that the backend connection will use the specified collation, mysql_real_connect() is using a different collation. For example, using collation 305 will lead to use collation 49 (305-256).
Solution:
When a collation id greater than 255 is detected, the default collation for that character set is used. ProxySQL will later issue a SET NAMES ... COLLATE to address the mismatch.