/****************************************************** Cursor read (c) 1997 Innobase Oy Created 2/16/1997 Heikki Tuuri *******************************************************/ #ifndef read0read_h #define read0read_h #include "univ.i" #include "ut0byte.h" #include "ut0lst.h" #include "trx0trx.h" #include "read0types.h" /************************************************************************* Opens a read view where exactly the transactions serialized before this point in time are seen in the view. */ read_view_t* read_view_open_now( /*===============*/ /* out, own: read view struct */ trx_t* cr_trx, /* in: creating transaction, or NULL */ mem_heap_t* heap); /* in: memory heap from which allocated */ /************************************************************************* Makes a copy of the oldest existing read view, or opens a new. The view must be closed with ..._close. */ read_view_t* read_view_oldest_copy_or_open_new( /*==============================*/ /* out, own: read view struct */ trx_t* cr_trx, /* in: creating transaction, or NULL */ mem_heap_t* heap); /* in: memory heap from which allocated */ /************************************************************************* Closes a read view. */ void read_view_close( /*============*/ read_view_t* view); /* in: read view */ /************************************************************************* Checks if a read view sees the specified transaction. */ UNIV_INLINE ibool read_view_sees_trx_id( /*==================*/ /* out: TRUE if sees */ read_view_t* view, /* in: read view */ dulint trx_id); /* in: trx id */ /* Read view lists the trx ids of those transactions for which a consistent read should not see the modifications to the database. */ struct read_view_struct{ ibool can_be_too_old; /* TRUE if the system has had to purge old versions which this read view should be able to access: the read view can bump into the DB_MISSING_HISTORY error */ dulint low_limit_no; /* The view does not need to see the undo logs for transactions whose transaction number is strictly smaller (<) than this value: they can be removed in purge if not needed by other views */ dulint low_limit_id; /* The read should not see any transaction with trx id >= this value */ dulint up_limit_id; /* The read should see all trx ids which are strictly smaller (<) than this value */ ulint n_trx_ids; /* Number of cells in the trx_ids array */ dulint* trx_ids; /* Additional trx ids which the read should not see: typically, these are the active transactions at the time when the read is serialized, except the reading transaction itself; the trx ids in this array are in a descending order */ trx_t* creator; /* Pointer to the creating transaction, or NULL if used in purge */ UT_LIST_NODE_T(read_view_t) view_list; /* List of read views in trx_sys */ }; #ifndef UNIV_NONINL #include "read0read.ic" #endif #endif