Commit 55aa8dc0 authored by marko's avatar marko

branches/zip: struct read_view_struct: Add clarifying comments about

low_limit_id and up_limit_id.
parent 7d1a0d65
......@@ -133,16 +133,21 @@ struct read_view_struct{
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 */
with trx id >= this value. In other words,
this is the "high water mark". */
dulint up_limit_id; /* The read should see all trx ids which
are strictly smaller (<) than this value */
are strictly smaller (<) than this value.
In other words,
this is the "low water mark". */
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 */
descending order. These trx_ids should be
between the "low" and "high" water marks,
that is, up_limit_id and low_limit_id. */
dulint creator_trx_id; /* trx id of creating transaction, or
(0, 0) used in purge */
UT_LIST_NODE_T(read_view_t) view_list;
......
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