was large enough to be batched and the tuples fell into a batch where
there were no inner tuples at all. Thanks to Xiaoyu Wang for finding a
test case that exposed this long-standing bug.
creating a new tuple. This is just for debugging sanity, though, since
nothing should be paying any attention to xmax when the HEAP_XMAX_INVALID
bit is set.
pg_subtrans --- what we need is the oldest xmin of any snapshot in use
in the current top transaction. Introduce a new variable TransactionXmin
to play this role. Fixes intermittent regression failure reported by
Neil Conway.
as per recent discussions. Invent SubTransactionIds that are managed like
CommandIds (ie, counter is reset at start of each top transaction), and
use these instead of TransactionIds to keep track of subtransaction status
in those modules that need it. This means that a subtransaction does not
need an XID unless it actually inserts/modifies rows in the database.
Accordingly, don't assign it an XID nor take a lock on the XID until it
tries to do that. This saves a lot of overhead for subtransactions that
are only used for error recovery (eg plpgsql exceptions). Also, arrange
to release a subtransaction's XID lock as soon as the subtransaction
exits, in both the commit and abort cases. This avoids holding many
unique locks after a long series of subtransactions. The price is some
additional overhead in XactLockTableWait, but that seems acceptable.
Finally, restructure the state machine in xact.c to have a more orthogonal
set of states for subtransactions.
mode see a fresh snapshot for each command in the function, rather than
using the latest interactive command's snapshot. Also, suppress fresh
snapshots as well as CommandCounterIncrement inside STABLE and IMMUTABLE
functions, instead using the snapshot taken for the most closely nested
regular query. (This behavior is only sane for read-only functions, so
the patch also enforces that such functions contain only SELECT commands.)
As per my proposal of 6-Sep-2004; I note that I floated essentially the
same proposal on 19-Jun-2002, but that discussion tailed off without any
action. Since 8.0 seems like the right place to be taking possibly
nontrivial backwards compatibility hits, let's get it done now.
((Snapshot) NULL) can no longer be confused with a valid snapshot,
as per my recent suggestion. Define a macro InvalidSnapshot for 0.
Use InvalidSnapshot instead of SnapshotAny as the do-nothing special
case for heap_update and heap_delete crosschecks; this seems a little
cleaner even though the behavior is really the same.
rather than when returning to the idle loop. This makes no particular
difference for interactively-issued queries, but it makes a big difference
for queries issued within functions: trigger execution now occurs before
the calling function is allowed to proceed. This responds to numerous
complaints about nonintuitive behavior of foreign key checking, such as
http://archives.postgresql.org/pgsql-bugs/2004-09/msg00020.php, and
appears to be required by the SQL99 spec.
Also take the opportunity to simplify the data structures used for the
pending-trigger list, rename them for more clarity, and squeeze out a
bit of space.
status. In particular, I see no reason for deferredTriggerCheckState
to make an explicit entry to note that a particular trigger has its
default state --- that just clutters a list that should normally be
empty or very short. I have plans to revise this module much more
heavily, but this is a simple separable improvement.
Asserts would lead to a server core dump if an error occurred while
trying to abort a failed subtransaction (thereby leading to re-execution
of whatever parts of AbortSubTransaction had already run). This of course
does not prevent such an error from creating an infinite loop, but at
least we don't make the situation worse. Responds to an open item on
the subtransactions to-do list.
elog() emulation code always calls errstart with ERROR error level.
This means that a recursive error call triggered by elog would do
MemoryContextReset(ErrorContext), whether or not this was actually
appropriate. I'm surprised we haven't seen this in the field...
Messages of less than ERROR severity should never be promoted (this
fixes Gaetano Mendola's problem with a COMMERROR becoming a PANIC,
and is obvious in hindsight anyway). Do all promotion in errstart
not errfinish, to ensure that output decisions are made correctly;
the former coding could suppress logging of promoted errors, which
doesn't seem like a good idea. Eliminate some redundant code too.
use of already-freed strings, other silliness. Also fix reporting of
config file syntax errors so that it actually works reasonably well
(eg, points at the correct line). Use palloc instead of malloc for
temporary storage to reduce code clutter.
not supposed to (fixes problem with postmaster aborting due to mistaken
postgresql.conf change); don't call superuser() when not inside a
transaction (fixes coredump when, eg, try to set log_statement from
PGOPTIONS); some message style guidelines enforcement.
default tablespace --- they should always go in the database's default
tablespace. Adjust heap_create() API so that it is passed the relkind
to make this easier; should simplify any further tweaking of the same
sort.
