Merged
Conversation
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.
Closed
7 tasks
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
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.