Обсуждение: pgsql: Done! < * Merge xmin/xmax/cmin/cmax back into three header

Log Message:
-----------
Done!

< * Merge xmin/xmax/cmin/cmax back into three header fields
<
<   Before subtransactions, there used to be only three fields needed to
<   store these four values. This was possible because only the current
<   transaction looks at the cmin/cmax values. If the current transaction
<   created and expired the row the fields stored where xmin (same as
<   xmax), cmin, cmax, and if the transaction was expiring a row from a
<   another transaction, the fields stored were xmin (cmin was not
<   needed), xmax, and cmax. Such a system worked because a transaction
<   could only see rows from another completed transaction. However,
<   subtransactions can see rows from outer transactions, and once the
<   subtransaction completes, the outer transaction continues, requiring
<   the storage of all four fields. With subtransactions, an outer
<   transaction can create a row, a subtransaction expire it, and when the
<   subtransaction completes, the outer transaction still has to have
<   proper visibility of the row's cmin, for example, for cursors.
<
<   One possible solution is to create a phantom cid which represents a
<   cmin/cmax pair and is stored in local memory.  Another idea is to
<   store both cmin and cmax only in local memory.
<
> * -Merge xmin/xmax/cmin/cmax back into three header fields

Modified Files:
--------------
    pgsql/doc:
        TODO (r1.2082 -> r1.2083)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.2082&r2=1.2083)
    pgsql/doc/src/FAQ:
        TODO.html (r1.583 -> r1.584)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.583&r2=1.584)