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  1. MariaDB Server
  2. MDEV-16470

Session user variables tracker

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    Description

      When using a proxy, such as MaxScale to do read/write split, It is not easy to keep session state consistent between different backends, especially for session user variables; When execute stored procedure, or do some select with user variable modification,It is hard for proxy to notice that a variable was changed, and get the lasted value;
      For example,

      select a, b from (select (@id:=@id+1) as id, a, b from t group by c order by d) tt where id < 10;
      		 
      select @a:=b, c from t
      		 
      ...

      Currently, Maxscale route these queries to every backends or route all to master, it is not efficient and sometimes not correct;

      So we suggest that server provide a session user variables tracker to inform proxy the what variable changed, and the lasted value, then propagate the results to other backends.

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          blocks

          New Feature - A new feature of the product, which has yet to be developed. MXS-1756 Keep session consistent via session variable tracker

          • Major - Major loss of function.
          • Closed
          causes

          Bug - A problem which impairs or prevents the functions of the product. MDEV-22709 Assertion `store.length() <= (256L*256L*256L-1)' failed in net_send_ok

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed
          includes

          Bug - A problem which impairs or prevents the functions of the product. MDEV-22709 Assertion `store.length() <= (256L*256L*256L-1)' failed in net_send_ok

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-22574 user variable tracking has no tests and C/C support

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

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            People

              sanja Oleksandr Byelkin
              dapeng dapeng huang
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              Dates

                Created:
                Updated:

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