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  1. MariaDB Server
  2. MDEV-6910

Item_cache::is_null() returns incorrect result inside storage engine's cond_push()

        Details

        • Type: Bug
        • Status: Open
        • Priority: Major
        • Resolution: Unresolved
        • Affects Version/s: 10.0.14
        • Fix Version/s: 10.0
        • Component/s: None
        • Labels:
          None

          Description

          Current implementation of Item_cache::is_null() in MariaDB comes from http://bazaar.launchpad.net/~maria-captains/maria/10.0/revision/2502.313.1 which was fixing incorrect query results. MySQL 5.6 apparently had similar problems with incorrect query results, but they fixed Item_cache::is_null() slightly differently: http://bazaar.launchpad.net/~mysql/mysql-server/5.6/revision/3690.1.115. And it turns out that MySQL's implementation is correct while MariaDB's is not.

          Unfortunately I don't know if it's possible to exhibit the problem using some SQL – the test from MySQL's patch passes on MariaDB. But the difference for us was in the custom storage engine inside the cond_push() function. Apparently by the time this function is called Item_cache doesn't have a cached value yet and thus is_null() always return true leading to incorrect behavior of the storage engine.

          Please incorporate MySQL's implementation of Item_cache::is_null() and if possible add a test for this specific problem.

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                danblack Daniel Black added a comment -

                seems to still be the case https://github.com/MariaDB/server/blob/10.0/sql/item.h#L4560

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                danblack Daniel Black added a comment - seems to still be the case https://github.com/MariaDB/server/blob/10.0/sql/item.h#L4560

                  People

                  • Assignee:
                    sanja Oleksandr Byelkin
                    Reporter:
                    pivanof Pavel Ivanov
                  • Votes:
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                    4 Start watching this issue

                    Dates

                    • Created:
                      Updated: