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Improve confusing comment for HeapTupleSatisfiesNow, per gripe from Greg Stark.

This commit is contained in:
Tom Lane 2006-09-15 16:39:32 +00:00
parent fa6f9ceab6
commit 0498a08e66
1 changed files with 11 additions and 12 deletions
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23
src/backend/utils/time/tqual.c
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@ -32,7 +32,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/time/tqual.c,v 1.96 2006/09/03 15:59:39 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/time/tqual.c,v 1.97 2006/09/15 16:39:32 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -253,19 +253,18 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple, Buffer buffer)
*
* The satisfaction of "now" requires the following:
*
* ((Xmin == my-transaction && changed by the current transaction
* Cmin != my-command && but not by this command, and
* (Xmax is null || the row has not been deleted, or
* (Xmax == my-transaction && it was deleted by the current transaction
* Cmax != my-command))) but not by this command,
* ((Xmin == my-transaction && inserted by the current transaction
* Cmin < my-command && before this command, and
* (Xmax is null || the row has not been deleted, or
* (Xmax == my-transaction && it was deleted by the current transaction
* Cmax >= my-command))) but not before this command,
* || or
*
* (Xmin is committed && the row was modified by a committed transaction, and
* (Xmin is committed && the row was inserted by a committed transaction, and
* (Xmax is null || the row has not been deleted, or
* (Xmax == my-transaction && the row is being deleted by this command, or
* Cmax == my-command) ||
* (Xmax is not committed && the row was deleted by another transaction
* Xmax != my-transaction)))) that has not been committed
* (Xmax == my-transaction && the row is being deleted by this transaction
* Cmax >= my-command) || but it's not deleted "yet", or
* (Xmax != my-transaction && the row was deleted by another transaction
* Xmax is not committed)))) that has not been committed
*
* mao says 17 march 1993: the tests in this routine are correct;
* if you think they're not, you're wrong, and you should think