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struct read_view_struct{
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  ulint    type;  /*!< VIEW_NORMAL, VIEW_HIGH_GRANULARITY */
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  undo_no_t  undo_no;/*!< 0 or if type is
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        VIEW_HIGH_GRANULARITY
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        transaction undo_no when this high-granularity
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        consistent read view was created */
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  trx_id_t  low_limit_no;
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        /*!< The view does not need to see the undo
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        logs for transactions whose transaction number
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        is strictly smaller (<) than this value: they
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        can be removed in purge if not needed by other
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        views */
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  trx_id_t  low_limit_id;
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        /*!< The read should not see any transaction
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        with trx id >= this value. In other words,
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        this is the "high water mark". */
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  trx_id_t  up_limit_id;
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        /*!< The read should see all trx ids which
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        are strictly smaller (<) than this value.
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        In other words,
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        this is the "low water mark". */
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  ulint    n_trx_ids;
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        /*!< Number of cells in the trx_ids array */
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  trx_id_t*  trx_ids;/*!< Additional trx ids which the read should
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        not see: typically, these are the active
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        transactions at the time when the read is
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        serialized, except the reading transaction
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        itself; the trx ids in this array are in a
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        descending order. These trx_ids should be
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        between the "low" and "high" water marks,
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        that is, up_limit_id and low_limit_id. */
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  trx_id_t  creator_trx_id;
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        /*!< trx id of creating transaction, or
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        0 used in purge */
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  UT_LIST_NODE_T(read_view_t) view_list;
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        /*!< List of read views in trx_sys */
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};

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create table ab(a int primary key, b int);
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Tx1:
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begin;
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select * from ab; // empty set
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Tx2:
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begin;
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insert into ab values(1,1);
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commit;
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Tx1:
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select * from ab; // empty set, expected phantom read missing.
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update ab set b = 2 where a = 1; // 1 row affected.
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select * from ab; // 1 row. phantom read here!!!!
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commit;