Gregory Stark <stark@enterprisedb.com> writes:
> Tom Lane <tgl@sss.pgh.pa.us> writes:
>> --- and because the entries are surely added in increasing XID order,
>> such an array could be binary-searched.
> If they're only added if they write to disk then isn't it possible to add them
> out of order? Start a child transaction, start a child of that one and write
> to disk, then exit the grandchild and write to disk in the first
> child?
No, because we enforce child XID > parent XID. In the case above, the
child xact would be given an XID when the grandchild needs one --- see
recursion in AssignSubTransactionId(). The actually slightly shaky
assumption above is that children of the same parent xact must subcommit
in numerical order ... but as long as we have strict nesting of subxacts
I think this must be so.
regards, tom lane