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本帖最后由 justin033 于 2010-09-11 00:41 编辑
回复 1# justlooks
low_limit_no 用来判断purge记录
If the secondary key record is delete marked it's corresponding
clustered record can be already be purged only if records
trx_id < low_limit_no. Purge can't remove any record deleted by a
transaction which was active when cursor was created. But, we still
may have a deleted secondary key record but no clustered record. But,
this is not a problem because this case is handled in
row_sel_get_clust_rec() function which is called
whenever we note that this read view does not see trx_id in the
record. Thus, we see correct version. |
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