c8h4/postgresql
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Create an infrastructure for parallel computation in PostgreSQL.

Browse source 
This does four basic things.  First, it provides convenience routines
to coordinate the startup and shutdown of parallel workers.  Second,
it synchronizes various pieces of state (e.g. GUCs, combo CID
mappings, transaction snapshot) from the parallel group leader to the
worker processes.  Third, it prohibits various operations that would
result in unsafe changes to that state while parallelism is active.
Finally, it propagates events that would result in an ErrorResponse,
NoticeResponse, or NotifyResponse message being sent to the client
from the parallel workers back to the master, from which they can then
be sent on to the client.

Robert Haas, Amit Kapila, Noah Misch, Rushabh Lathia, Jeevan Chalke.
Suggestions and review from Andres Freund, Heikki Linnakangas, Noah
Misch, Simon Riggs, Euler Taveira, and Jim Nasby.
This commit is contained in:
Robert Haas 2015-04-30 15:02:14 -04:00
parent 669c7d20e6
commit 924bcf4f16
37 changed files with 2499 additions and 47 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
contrib/postgres_fdw/connection.c
View file

@ -546,6 +546,7 @@ pgfdw_xact_callback(XactEvent event, void *arg)
switch (event)
{
case XACT_EVENT_PARALLEL_PRE_COMMIT:
case XACT_EVENT_PRE_COMMIT:
/* Commit all remote transactions during pre-commit */
do_sql_command(entry->conn, "COMMIT TRANSACTION");
@ -588,11 +589,13 @@ pgfdw_xact_callback(XactEvent event, void *arg)
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot prepare a transaction that modified remote tables")));
break;
case XACT_EVENT_PARALLEL_COMMIT:
case XACT_EVENT_COMMIT:
case XACT_EVENT_PREPARE:
/* Pre-commit should have closed the open transaction */
elog(ERROR, "missed cleaning up connection during pre-commit");
break;
case XACT_EVENT_PARALLEL_ABORT:
case XACT_EVENT_ABORT:
/* Assume we might have lost track of prepared statements */
entry->have_error = true;

55
src/backend/access/heap/heapam.c
View file

@ -42,6 +42,7 @@
#include "access/heapam_xlog.h"
#include "access/hio.h"
#include "access/multixact.h"
#include "access/parallel.h"
#include "access/relscan.h"
#include "access/sysattr.h"
#include "access/transam.h"
@ -1051,7 +1052,13 @@ relation_open(Oid relationId, LOCKMODE lockmode)
/* Make note that we've accessed a temporary relation */
if (RelationUsesLocalBuffers(r))
{
if (IsParallelWorker())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot access temporary tables during a parallel operation")));
MyXactAccessedTempRel = true;
}
pgstat_initstats(r);
@ -1097,7 +1104,13 @@ try_relation_open(Oid relationId, LOCKMODE lockmode)
/* Make note that we've accessed a temporary relation */
if (RelationUsesLocalBuffers(r))
{
if (IsParallelWorker())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot access temporary tables during a parallel operation")));
MyXactAccessedTempRel = true;
}
pgstat_initstats(r);
@ -2237,6 +2250,17 @@ static HeapTuple
heap_prepare_insert(Relation relation, HeapTuple tup, TransactionId xid,
CommandId cid, int options)
{
/*
* For now, parallel operations are required to be strictly read-only.
* Unlike heap_update() and heap_delete(), an insert should never create
* a combo CID, so it might be possible to relax this restriction, but
* not without more thought and testing.
*/
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot insert tuples during a parallel operation")));
if (relation->rd_rel->relhasoids)
{
#ifdef NOT_USED
@ -2648,6 +2672,16 @@ heap_delete(Relation relation, ItemPointer tid,
Assert(ItemPointerIsValid(tid));
/*
* Forbid this during a parallel operation, lets it allocate a combocid.
* Other workers might need that combocid for visibility checks, and we
* have no provision for broadcasting it to them.
*/
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot delete tuples during a parallel operation")));
block = ItemPointerGetBlockNumber(tid);
buffer = ReadBuffer(relation, block);
page = BufferGetPage(buffer);
@ -3099,6 +3133,16 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
Assert(ItemPointerIsValid(otid));
/*
* Forbid this during a parallel operation, lets it allocate a combocid.
* Other workers might need that combocid for visibility checks, and we
* have no provision for broadcasting it to them.
*/
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot update tuples during a parallel operation")));
/*
* Fetch the list of attributes to be checked for HOT update. This is
* wasted effort if we fail to update or have to put the new tuple on a
@ -5400,6 +5444,17 @@ heap_inplace_update(Relation relation, HeapTuple tuple)
uint32 oldlen;
uint32 newlen;
/*
* For now, parallel operations are required to be strictly read-only.
* Unlike a regular update, this should never create a combo CID, so it
* might be possible to relax this restriction, but not without more
* thought and testing. It's not clear that it would be useful, anyway.
*/
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot update tuples during a parallel operation")));
buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(&(tuple->t_self)));
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
page = (Page) BufferGetPage(buffer);

2
src/backend/access/transam/Makefile
View file

@ -12,7 +12,7 @@ subdir = src/backend/access/transam
top_builddir = ../../../..
include $(top_builddir)/src/Makefile.global
OBJS = clog.o commit_ts.o multixact.o rmgr.o slru.o subtrans.o \
OBJS = clog.o commit_ts.o multixact.o parallel.o rmgr.o slru.o subtrans.o \
timeline.o transam.o twophase.o twophase_rmgr.o varsup.o \
xact.o xlog.o xlogarchive.o xlogfuncs.o \
xloginsert.o xlogreader.o xlogutils.o

223
src/backend/access/transam/README.parallel Normal file
View file

@ -0,0 +1,223 @@
Overview
========
PostgreSQL provides some simple facilities to make writing parallel algorithms
easier. Using a data structure called a ParallelContext, you can arrange to
launch background worker processes, initialize their state to match that of
the backend which initiated parallelism, communicate with them via dynamic
shared memory, and write reasonably complex code that can run either in the
user backend or in one of the parallel workers without needing to be aware of
where it's running.
The backend which starts a parallel operation (hereafter, the initiating
backend) starts by creating a dynamic shared memory segment which will last
for the lifetime of the parallel operation. This dynamic shared memory segment
will contain (1) a shm_mq that can be used to transport errors (and other
messages reported via elog/ereport) from the worker back to the initiating
backend; (2) serialized representations of the initiating backend's private
state, so that the worker can synchronize its state with of the initiating
backend; and (3) any other data structures which a particular user of the
ParallelContext data structure may wish to add for its own purposes. Once
the initiating backend has initialized the dynamic shared memory segment, it
asks the postmaster to launch the appropriate number of parallel workers.
These workers then connect to the dynamic shared memory segment, initiate
their state, and then invoke the appropriate entrypoint, as further detailed
below.
Error Reporting
===============
When started, each parallel worker begins by attaching the dynamic shared
memory segment and locating the shm_mq to be used for error reporting; it
redirects all of its protocol messages to this shm_mq. Prior to this point,
any failure of the background worker will not be reported to the initiating
backend; from the point of view of the initiating backend, the worker simply
failed to start. The initiating backend must anyway be prepared to cope
with fewer parallel workers than it originally requested, so catering to
this case imposes no additional burden.
Whenever a new message (or partial message; very large messages may wrap) is
sent to the error-reporting queue, PROCSIG_PARALLEL_MESSAGE is sent to the
initiating backend. This causes the next CHECK_FOR_INTERRUPTS() in the
initiating backend to read and rethrow the message. For the most part, this
makes error reporting in parallel mode "just work". Of course, to work
properly, it is important that the code the initiating backend is executing
CHECK_FOR_INTERRUPTS() regularly and avoid blocking interrupt processing for
long periods of time, but those are good things to do anyway.
(A currently-unsolved problem is that some messages may get written to the
system log twice, once in the backend where the report was originally
generated, and again when the initiating backend rethrows the message. If
we decide to suppress one of these reports, it should probably be second one;
otherwise, if the worker is for some reason unable to propagate the message
back to the initiating backend, the message will be lost altogether.)
State Sharing
=============
It's possible to write C code which works correctly without parallelism, but
which fails when parallelism is used. No parallel infrastructure can
completely eliminate this problem, because any global variable is a risk.
There's no general mechanism for ensuring that every global variable in the
worker will have the same value that it does in the initiating backend; even
if we could ensure that, some function we're calling could update the variable
after each call, and only the backend where that update is performed will see
the new value. Similar problems can arise with any more-complex data
structure we might choose to use. For example, a pseudo-random number
generator should, given a particular seed value, produce the same predictable
series of values every time. But it does this by relying on some private
state which won't automatically be shared between cooperating backends. A
parallel-safe PRNG would need to store its state in dynamic shared memory, and
would require locking. The parallelism infrastructure has no way of knowing
whether the user intends to call code that has this sort of problem, and can't
do anything about it anyway.
Instead, we take a more pragmatic approach. First, we try to make as many of
the operations that are safe outside of parallel mode work correctly in
parallel mode as well. Second, we try to prohibit common unsafe operations
via suitable error checks. These checks are intended to catch 100% of
unsafe things that a user might do from the SQL interface, but code written
in C can do unsafe things that won't trigger these checks. The error checks
are engaged via EnterParallelMode(), which should be called before creating
a parallel context, and disarmed via ExitParallelMode(), which should be
called after all parallel contexts have been destroyed. The most
significant restriction imposed by parallel mode is that all operations must
be strictly read-only; we allow no writes to the database and no DDL. We
might try to relax these restrictions in the future.
To make as many operations as possible safe in parallel mode, we try to copy
the most important pieces of state from the initiating backend to each parallel
worker. This includes:
- The set of libraries dynamically loaded by dfmgr.c.
- The authenticated user ID and current database. Each parallel worker
will connect to the same database as the initiating backend, using the
same user ID.
- The values of all GUCs. Accordingly, permanent changes to the value of
any GUC are forbidden while in parallel mode; but temporary changes,
such as entering a function with non-NULL proconfig, are OK.
- The current subtransaction's XID, the top-level transaction's XID, and
the list of XIDs considered current (that is, they are in-progress or
subcommitted). This information is needed to ensure that tuple visibility
checks return the same results in the worker as they do in the
initiating backend. See also the section Transaction Integration, below.
- The combo CID mappings. This is needed to ensure consistent answers to
tuple visibility checks. The need to synchronize this data structure is
a major reason why we can't support writes in parallel mode: such writes
might create new combo CIDs, and we have no way to let other workers
(or the initiating backend) know about them.
- The transaction snapshot.
- The active snapshot, which might be different from the transaction
snapshot.
- The currently active user ID and security context. Note that this is
the fourth user ID we restore: the initial step of binding to the correct
database also involves restoring the authenticated user ID. When GUC
values are restored, this incidentally sets SessionUserId and OuterUserId
to the correct values. This final step restores CurrentUserId.
To prevent undetected or unprincipled deadlocks when running in parallel mode,
this could should eventually handle heavyweight locks in some way. This is
not implemented yet.
Transaction Integration
=======================
Regardless of what the TransactionState stack looks like in the parallel
leader, each parallel worker ends up with a stack of depth 1. This stack
entry is marked with the special transaction block state
TBLOCK_PARALLEL_INPROGRESS so that it's not confused with an ordinary
toplevel transaction. The XID of this TransactionState is set to the XID of
the innermost currently-active subtransaction in the initiating backend. The
initiating backend's toplevel XID, and the XIDs of all current (in-progress
or subcommitted) XIDs are stored separately from the TransactionState stack,
but in such a way that GetTopTransactionId(), GetTopTransactionIdIfAny(), and
TransactionIdIsCurrentTransactionId() return the same values that they would
in the initiating backend. We could copy the entire transaction state stack,
but most of it would be useless: for example, you can't roll back to a
savepoint from within a parallel worker, and there are no resources to
associated with the memory contexts or resource owners of intermediate
subtransactions.
No meaningful change to the transaction state can be made while in parallel
mode. No XIDs can be assigned, and no subtransactions can start or end,
because we have no way of communicating these state changes to cooperating
backends, or of synchronizing them. It's clearly unworkable for the initiating
backend to exit any transaction or subtransaction that was in progress when
parallelism was started before all parallel workers have exited; and it's even
more clearly crazy for a parallel worker to try to subcommit or subabort the
current subtransaction and execute in some other transaction context than was
present in the initiating backend. It might be practical to allow internal
sub-transactions (e.g. to implement a PL/pgsql EXCEPTION block) to be used in
parallel mode, provided that they are XID-less, because other backends
wouldn't really need to know about those transactions or do anything
differently because of them. Right now, we don't even allow that.
At the end of a parallel operation, which can happen either because it
completed successfully or because it was interrupted by an error, parallel
workers associated with that operation exit. In the error case, transaction
abort processing in the parallel leader kills of any remaining workers, and
the parallel leader then waits for them to die. In the case of a successful
parallel operation, the parallel leader does not send any signals, but must
wait for workers to complete and exit of their own volition. In either
case, it is very important that all workers actually exit before the
parallel leader cleans up the (sub)transaction in which they were created;
otherwise, chaos can ensue. For example, if the leader is rolling back the
transaction that created the relation being scanned by a worker, the
relation could disappear while the worker is still busy scanning it. That's
not safe.
Generally, the cleanup performed by each worker at this point is similar to
top-level commit or abort. Each backend has its own resource owners: buffer
pins, catcache or relcache reference counts, tuple descriptors, and so on
are managed separately by each backend, and must free them before exiting.
There are, however, some important differences between parallel worker
commit or abort and a real top-level transaction commit or abort. Most
importantly:
- No commit or abort record is written; the initiating backend is
responsible for this.
- Cleanup of pg_temp namespaces is not done. Parallel workers cannot
safely access the initiating backend's pg_temp namespace, and should
not create one of their own.
Coding Conventions
===================
Before beginning any parallel operation, call EnterParallelMode(); after all
parallel operations are completed, call ExitParallelMode(). To actually
parallelize a particular operation, use a ParallelContext. The basic coding
pattern looks like this:
EnterParallelMode(); /* prohibit unsafe state changes */
pcxt = CreateParallelContext(entrypoint, nworkers);
/* Allow space for application-specific data here. */
shm_toc_estimate_chunk(&pcxt->estimator, size);
shm_toc_estimate_keys(&pcxt->estimator, keys);
InitializeParallelDSM(pcxt); /* create DSM and copy state to it */
/* Store the data for which we reserved space. */
space = shm_toc_allocate(pcxt->toc, size);
shm_toc_insert(pcxt->toc, key, space);
LaunchParallelWorkers(pcxt);
/* do parallel stuff */
WaitForParallelWorkersToFinish(pcxt);
/* read any final results from dynamic shared memory */
DestroyParallelContext(pcxt);
ExitParallelMode();

1007
src/backend/access/transam/parallel.c Normal file
View file

File diff suppressed because it is too large Load diff

7
src/backend/access/transam/varsup.c
View file

@ -49,6 +49,13 @@ GetNewTransactionId(bool isSubXact)
{
TransactionId xid;
/*
* Workers synchronize transaction state at the beginning of each parallel
* operation, so we can't account for new XIDs after that point.
*/
if (IsInParallelMode())
elog(ERROR, "cannot assign TransactionIds during a parallel operation");
/*
* During bootstrap initialization, we return the special bootstrap
* transaction id.

486
src/backend/access/transam/xact.c
View file

@ -22,6 +22,7 @@
#include "access/commit_ts.h"
#include "access/multixact.h"
#include "access/parallel.h"
#include "access/subtrans.h"
#include "access/transam.h"
#include "access/twophase.h"
@ -51,6 +52,7 @@
#include "storage/procarray.h"
#include "storage/sinvaladt.h"
#include "storage/smgr.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/combocid.h"
#include "utils/guc.h"
@ -77,6 +79,33 @@ bool XactDeferrable;
int synchronous_commit = SYNCHRONOUS_COMMIT_ON;
/*
* When running as a parallel worker, we place only a single
* TransactionStateData on the parallel worker's state stack, and the XID
* reflected there will be that of the *innermost* currently-active
* subtransaction in the backend that initiated paralllelism. However,
* GetTopTransactionId() and TransactionIdIsCurrentTransactionId()
* need to return the same answers in the parallel worker as they would have
* in the user backend, so we need some additional bookkeeping.
*
* XactTopTransactionId stores the XID of our toplevel transaction, which
* will be the same as TopTransactionState.transactionId in an ordinary
* backend; but in a parallel backend, which does not have the entire
* transaction state, it will instead be copied from the backend that started
* the parallel operation.
*
* nParallelCurrentXids will be 0 and ParallelCurrentXids NULL in an ordinary
* backend, but in a parallel backend, nParallelCurrentXids will contain the
* number of XIDs that need to be considered current, and ParallelCurrentXids
* will contain the XIDs themselves. This includes all XIDs that were current
* or sub-committed in the parent at the time the parallel operation began.
* The XIDs are stored sorted in numerical order (not logical order) to make
* lookups as fast as possible.
*/
TransactionId XactTopTransactionId = InvalidTransactionId;
int nParallelCurrentXids = 0;
TransactionId *ParallelCurrentXids;
/*
* MyXactAccessedTempRel is set when a temporary relation is accessed.
* We don't allow PREPARE TRANSACTION in that case. (This is global
@ -113,6 +142,7 @@ typedef enum TBlockState
/* transaction block states */
TBLOCK_BEGIN, /* starting transaction block */
TBLOCK_INPROGRESS, /* live transaction */
TBLOCK_PARALLEL_INPROGRESS, /* live transaction inside parallel worker */
TBLOCK_END, /* COMMIT received */
TBLOCK_ABORT, /* failed xact, awaiting ROLLBACK */
TBLOCK_ABORT_END, /* failed xact, ROLLBACK received */
@ -154,6 +184,7 @@ typedef struct TransactionStateData
bool prevXactReadOnly; /* entry-time xact r/o state */
bool startedInRecovery; /* did we start in recovery? */
bool didLogXid; /* has xid been included in WAL record? */
int parallelModeLevel; /* Enter/ExitParallelMode counter */
struct TransactionStateData *parent; /* back link to parent */
} TransactionStateData;
@ -184,6 +215,7 @@ static TransactionStateData TopTransactionStateData = {
false, /* entry-time xact r/o state */
false, /* startedInRecovery */
false, /* didLogXid */
0, /* parallelMode */
NULL /* link to parent state block */
};
@ -353,9 +385,9 @@ IsAbortedTransactionBlockState(void)
TransactionId
GetTopTransactionId(void)
{
if (!TransactionIdIsValid(TopTransactionStateData.transactionId))
if (!TransactionIdIsValid(XactTopTransactionId))
AssignTransactionId(&TopTransactionStateData);
return TopTransactionStateData.transactionId;
return XactTopTransactionId;
}
/*
@ -368,7 +400,7 @@ GetTopTransactionId(void)
TransactionId
GetTopTransactionIdIfAny(void)
{
return TopTransactionStateData.transactionId;
return XactTopTransactionId;
}
/*
@ -461,6 +493,13 @@ AssignTransactionId(TransactionState s)
Assert(!TransactionIdIsValid(s->transactionId));
Assert(s->state == TRANS_INPROGRESS);
/*
* Workers synchronize transaction state at the beginning of each
* parallel operation, so we can't account for new XIDs at this point.
*/
if (IsInParallelMode())
elog(ERROR, "cannot assign XIDs during a parallel operation");
/*
* Ensure parent(s) have XIDs, so that a child always has an XID later
* than its parent. Musn't recurse here, or we might get a stack overflow
@ -513,6 +552,8 @@ AssignTransactionId(TransactionState s)
* the Xid as "running". See GetNewTransactionId.
*/
s->transactionId = GetNewTransactionId(isSubXact);
if (!isSubXact)
XactTopTransactionId = s->transactionId;
if (isSubXact)
SubTransSetParent(s->transactionId, s->parent->transactionId, false);
@ -644,7 +685,16 @@ GetCurrentCommandId(bool used)
{
/* this is global to a transaction, not subtransaction-local */
if (used)
{
/*
* Forbid setting currentCommandIdUsed in parallel mode, because we
* have no provision for communicating this back to the master. We
* could relax this restriction when currentCommandIdUsed was already
* true at the start of the parallel operation.
*/
Assert(CurrentTransactionState->parallelModeLevel == 0);
currentCommandIdUsed = true;
}
return currentCommandId;
}
@ -737,6 +787,36 @@ TransactionIdIsCurrentTransactionId(TransactionId xid)
if (!TransactionIdIsNormal(xid))
return false;
/*
* In parallel workers, the XIDs we must consider as current are stored
* in ParallelCurrentXids rather than the transaction-state stack. Note
* that the XIDs in this array are sorted numerically rather than
* according to transactionIdPrecedes order.
*/
if (nParallelCurrentXids > 0)
{
int low,
high;
low = 0;
high = nParallelCurrentXids - 1;
while (low <= high)
{
int middle;
TransactionId probe;
middle = low + (high - low) / 2;
probe = ParallelCurrentXids[middle];
if (probe == xid)
return true;
else if (probe < xid)
low = middle + 1;
else
high = middle - 1;
}
return false;
}
/*
* We will return true for the Xid of the current subtransaction, any of
* its subcommitted children, any of its parents, or any of their
@ -790,6 +870,48 @@ TransactionStartedDuringRecovery(void)
return CurrentTransactionState->startedInRecovery;
}
/*
* EnterParallelMode
*/
void
EnterParallelMode(void)
{
TransactionState s = CurrentTransactionState;
Assert(s->parallelModeLevel >= 0);
++s->parallelModeLevel;
}
/*
* ExitParallelMode
*/
void
ExitParallelMode(void)
{
TransactionState s = CurrentTransactionState;
Assert(s->parallelModeLevel > 0);
Assert(s->parallelModeLevel > 1 || !ParallelContextActive());
--s->parallelModeLevel;
}
/*
* IsInParallelMode
*
* Are we in a parallel operation, as either the master or a worker? Check
* this to prohibit operations that change backend-local state expected to
* match across all workers. Mere caches usually don't require such a
* restriction. State modified in a strict push/pop fashion, such as the
* active snapshot stack, is often fine.
*/
bool
IsInParallelMode(void)
{
return CurrentTransactionState->parallelModeLevel != 0;
}
/*
* CommandCounterIncrement
*/
@ -804,6 +926,14 @@ CommandCounterIncrement(void)
*/
if (currentCommandIdUsed)
{
/*
* Workers synchronize transaction state at the beginning of each
* parallel operation, so we can't account for new commands after that
* point.
*/
if (IsInParallelMode())
elog(ERROR, "cannot start commands during a parallel operation");
currentCommandId += 1;
if (currentCommandId == InvalidCommandId)
{
@ -1650,6 +1780,8 @@ StartTransaction(void)
s = &TopTransactionStateData;
CurrentTransactionState = s;
Assert(XactTopTransactionId == InvalidTransactionId);
/*
* check the current transaction state
*/
@ -1779,6 +1911,9 @@ CommitTransaction(void)
{
TransactionState s = CurrentTransactionState;
TransactionId latestXid;
bool is_parallel_worker;
is_parallel_worker = (s->blockState == TBLOCK_PARALLEL_INPROGRESS);
ShowTransactionState("CommitTransaction");
@ -1812,7 +1947,8 @@ CommitTransaction(void)
break;
}
CallXactCallbacks(XACT_EVENT_PRE_COMMIT);
CallXactCallbacks(is_parallel_worker ? XACT_EVENT_PARALLEL_PRE_COMMIT
: XACT_EVENT_PRE_COMMIT);
/*
* The remaining actions cannot call any user-defined code, so it's safe
@ -1821,6 +1957,13 @@ CommitTransaction(void)
* the transaction-abort path.
*/
/* If we might have parallel workers, clean them up now. */
if (IsInParallelMode())
{
AtEOXact_Parallel(true);
s->parallelModeLevel = 0;
}
/* Shut down the deferred-trigger manager */
AfterTriggerEndXact(true);
@ -1859,10 +2002,28 @@ CommitTransaction(void)
*/
s->state = TRANS_COMMIT;
/*
* Here is where we really truly commit.
*/
latestXid = RecordTransactionCommit();
if (!is_parallel_worker)
{
/*
* We need to mark our XIDs as commited in pg_clog. This is where we
* durably commit.
*/
latestXid = RecordTransactionCommit();
}
else
{
/*
* We must not mark our XID committed; the parallel master is
* responsible for that.
*/
latestXid = InvalidTransactionId;
/*
* Make sure the master will know about any WAL we wrote before it
* commits.
*/
ParallelWorkerReportLastRecEnd(XactLastRecEnd);
}
TRACE_POSTGRESQL_TRANSACTION_COMMIT(MyProc->lxid);
@ -1889,7 +2050,8 @@ CommitTransaction(void)
* state.
*/
CallXactCallbacks(XACT_EVENT_COMMIT);
CallXactCallbacks(is_parallel_worker ? XACT_EVENT_PARALLEL_COMMIT
: XACT_EVENT_COMMIT);
ResourceOwnerRelease(TopTransactionResourceOwner,
RESOURCE_RELEASE_BEFORE_LOCKS,
@ -1937,7 +2099,7 @@ CommitTransaction(void)
AtEOXact_GUC(true, 1);
AtEOXact_SPI(true);
AtEOXact_on_commit_actions(true);
AtEOXact_Namespace(true);
AtEOXact_Namespace(true, is_parallel_worker);
AtEOXact_SMgr();
AtEOXact_Files();
AtEOXact_ComboCid();
@ -1962,6 +2124,9 @@ CommitTransaction(void)
s->nChildXids = 0;
s->maxChildXids = 0;
XactTopTransactionId = InvalidTransactionId;
nParallelCurrentXids = 0;
/*
* done with commit processing, set current transaction state back to
* default
@ -1985,6 +2150,8 @@ PrepareTransaction(void)
GlobalTransaction gxact;
TimestampTz prepared_at;
Assert(!IsInParallelMode());
ShowTransactionState("PrepareTransaction");
/*
@ -2204,7 +2371,7 @@ PrepareTransaction(void)
AtEOXact_GUC(true, 1);
AtEOXact_SPI(true);
AtEOXact_on_commit_actions(true);
AtEOXact_Namespace(true);
AtEOXact_Namespace(true, false);
AtEOXact_SMgr();
AtEOXact_Files();
AtEOXact_ComboCid();
@ -2229,6 +2396,9 @@ PrepareTransaction(void)
s->nChildXids = 0;
s->maxChildXids = 0;
XactTopTransactionId = InvalidTransactionId;
nParallelCurrentXids = 0;
/*
* done with 1st phase commit processing, set current transaction state
* back to default
@ -2247,6 +2417,7 @@ AbortTransaction(void)
{
TransactionState s = CurrentTransactionState;
TransactionId latestXid;
bool is_parallel_worker;
/* Prevent cancel/die interrupt while cleaning up */
HOLD_INTERRUPTS();
@ -2295,6 +2466,7 @@ AbortTransaction(void)
/*
* check the current transaction state
*/
is_parallel_worker = (s->blockState == TBLOCK_PARALLEL_INPROGRESS);
if (s->state != TRANS_INPROGRESS && s->state != TRANS_PREPARE)
elog(WARNING, "AbortTransaction while in %s state",
TransStateAsString(s->state));
@ -2318,6 +2490,13 @@ AbortTransaction(void)
*/
SetUserIdAndSecContext(s->prevUser, s->prevSecContext);
/* If in parallel mode, clean up workers and exit parallel mode. */
if (IsInParallelMode())
{
AtEOXact_Parallel(false);
s->parallelModeLevel = 0;
}
/*
* do abort processing
*/
@ -2330,9 +2509,23 @@ AbortTransaction(void)
/*
* Advertise the fact that we aborted in pg_clog (assuming that we got as
* far as assigning an XID to advertise).
* far as assigning an XID to advertise). But if we're inside a parallel
* worker, skip this; the user backend must be the one to write the abort
* record.
*/
latestXid = RecordTransactionAbort(false);
if (!is_parallel_worker)
latestXid = RecordTransactionAbort(false);
else
{
latestXid = InvalidTransactionId;
/*
* Since the parallel master won't get our value of XactLastRecEnd in this
* case, we nudge WAL-writer ourselves in this case. See related comments in
* RecordTransactionAbort for why this matters.
*/
XLogSetAsyncXactLSN(XactLastRecEnd);
}
TRACE_POSTGRESQL_TRANSACTION_ABORT(MyProc->lxid);
@ -2350,7 +2543,10 @@ AbortTransaction(void)
*/
if (TopTransactionResourceOwner != NULL)
{
CallXactCallbacks(XACT_EVENT_ABORT);
if (is_parallel_worker)
CallXactCallbacks(XACT_EVENT_PARALLEL_ABORT);
else
CallXactCallbacks(XACT_EVENT_ABORT);
ResourceOwnerRelease(TopTransactionResourceOwner,
RESOURCE_RELEASE_BEFORE_LOCKS,
@ -2371,7 +2567,7 @@ AbortTransaction(void)
AtEOXact_GUC(false, 1);
AtEOXact_SPI(false);
AtEOXact_on_commit_actions(false);
AtEOXact_Namespace(false);
AtEOXact_Namespace(false, is_parallel_worker);
AtEOXact_SMgr();
AtEOXact_Files();
AtEOXact_ComboCid();
@ -2423,6 +2619,10 @@ CleanupTransaction(void)
s->childXids = NULL;
s->nChildXids = 0;
s->maxChildXids = 0;
s->parallelModeLevel = 0;
XactTopTransactionId = InvalidTransactionId;
nParallelCurrentXids = 0;
/*
* done with abort processing, set current transaction state back to
@ -2476,6 +2676,7 @@ StartTransactionCommand(void)
/* These cases are invalid. */
case TBLOCK_STARTED:
case TBLOCK_BEGIN:
case TBLOCK_PARALLEL_INPROGRESS:
case TBLOCK_SUBBEGIN:
case TBLOCK_END:
case TBLOCK_SUBRELEASE:
@ -2511,11 +2712,13 @@ CommitTransactionCommand(void)
switch (s->blockState)
{
/*
* This shouldn't happen, because it means the previous
* These shouldn't happen. TBLOCK_DEFAULT means the previous
* StartTransactionCommand didn't set the STARTED state
* appropriately.
* appropriately, while TBLOCK_PARALLEL_INPROGRESS should be ended
* by EndParallelWorkerTranaction(), not this function.
*/
case TBLOCK_DEFAULT:
case TBLOCK_PARALLEL_INPROGRESS:
elog(FATAL, "CommitTransactionCommand: unexpected state %s",
BlockStateAsString(s->blockState));
break;
@ -2797,6 +3000,7 @@ AbortCurrentTransaction(void)
* ABORT state. We will stay in ABORT until we get a ROLLBACK.
*/
case TBLOCK_INPROGRESS:
case TBLOCK_PARALLEL_INPROGRESS:
AbortTransaction();
s->blockState = TBLOCK_ABORT;
/* CleanupTransaction happens when we exit TBLOCK_ABORT_END */
@ -3186,6 +3390,7 @@ BeginTransactionBlock(void)
* Already a transaction block in progress.
*/
case TBLOCK_INPROGRESS:
case TBLOCK_PARALLEL_INPROGRESS:
case TBLOCK_SUBINPROGRESS:
case TBLOCK_ABORT:
case TBLOCK_SUBABORT:
@ -3363,6 +3568,16 @@ EndTransactionBlock(void)
result = true;
break;
/*
* The user issued a COMMIT that somehow ran inside a parallel
* worker. We can't cope with that.
*/
case TBLOCK_PARALLEL_INPROGRESS:
ereport(FATAL,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot commit during a parallel operation")));
break;
/* These cases are invalid. */
case TBLOCK_DEFAULT:
case TBLOCK_BEGIN:
@ -3456,6 +3671,16 @@ UserAbortTransactionBlock(void)
s->blockState = TBLOCK_ABORT_PENDING;
break;
/*
* The user issued an ABORT that somehow ran inside a parallel
* worker. We can't cope with that.
*/
case TBLOCK_PARALLEL_INPROGRESS:
ereport(FATAL,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot abort during a parallel operation")));
break;
/* These cases are invalid. */
case TBLOCK_DEFAULT:
case TBLOCK_BEGIN:
@ -3485,6 +3710,18 @@ DefineSavepoint(char *name)
{
TransactionState s = CurrentTransactionState;
/*
* Workers synchronize transaction state at the beginning of each parallel
* operation, so we can't account for new subtransactions after that
* point. (Note that this check will certainly error out if s->blockState
* is TBLOCK_PARALLEL_INPROGRESS, so we can treat that as an invalid case
* below.)
*/
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot define savepoints during a parallel operation")));
switch (s->blockState)
{
case TBLOCK_INPROGRESS:
@ -3505,6 +3742,7 @@ DefineSavepoint(char *name)
case TBLOCK_DEFAULT:
case TBLOCK_STARTED:
case TBLOCK_BEGIN:
case TBLOCK_PARALLEL_INPROGRESS:
case TBLOCK_SUBBEGIN:
case TBLOCK_END:
case TBLOCK_SUBRELEASE:
@ -3539,6 +3777,18 @@ ReleaseSavepoint(List *options)
ListCell *cell;
char *name = NULL;
/*
* Workers synchronize transaction state at the beginning of each parallel
* operation, so we can't account for transaction state change after that
* point. (Note that this check will certainly error out if s->blockState
* is TBLOCK_PARALLEL_INPROGRESS, so we can treat that as an invalid case
* below.)
*/
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot release savepoints during a parallel operation")));
switch (s->blockState)
{
/*
@ -3562,6 +3812,7 @@ ReleaseSavepoint(List *options)
case TBLOCK_DEFAULT:
case TBLOCK_STARTED:
case TBLOCK_BEGIN:
case TBLOCK_PARALLEL_INPROGRESS:
case TBLOCK_SUBBEGIN:
case TBLOCK_END:
case TBLOCK_SUBRELEASE:
@ -3639,6 +3890,18 @@ RollbackToSavepoint(List *options)
ListCell *cell;
char *name = NULL;
/*
* Workers synchronize transaction state at the beginning of each parallel
* operation, so we can't account for transaction state change after that
* point. (Note that this check will certainly error out if s->blockState
* is TBLOCK_PARALLEL_INPROGRESS, so we can treat that as an invalid case
* below.)
*/
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot rollback to savepoints during a parallel operation")));
switch (s->blockState)
{
/*
@ -3663,6 +3926,7 @@ RollbackToSavepoint(List *options)
case TBLOCK_DEFAULT:
case TBLOCK_STARTED:
case TBLOCK_BEGIN:
case TBLOCK_PARALLEL_INPROGRESS:
case TBLOCK_SUBBEGIN:
case TBLOCK_END:
case TBLOCK_SUBRELEASE:
@ -3751,6 +4015,20 @@ BeginInternalSubTransaction(char *name)
{
TransactionState s = CurrentTransactionState;
/*
* Workers synchronize transaction state at the beginning of each parallel
* operation, so we can't account for new subtransactions after that point.
* We might be able to make an exception for the type of subtransaction
* established by this function, which is typically used in contexts where
* we're going to release or roll back the subtransaction before proceeding
* further, so that no enduring change to the transaction state occurs.
* For now, however, we prohibit this case along with all the others.
*/
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot start subtransactions during a parallel operation")));
switch (s->blockState)
{
case TBLOCK_STARTED:
@ -3773,6 +4051,7 @@ BeginInternalSubTransaction(char *name)
/* These cases are invalid. */
case TBLOCK_DEFAULT:
case TBLOCK_BEGIN:
case TBLOCK_PARALLEL_INPROGRESS:
case TBLOCK_SUBBEGIN:
case TBLOCK_SUBRELEASE:
case TBLOCK_SUBCOMMIT:
@ -3805,6 +4084,18 @@ ReleaseCurrentSubTransaction(void)
{
TransactionState s = CurrentTransactionState;
/*
* Workers synchronize transaction state at the beginning of each parallel
* operation, so we can't account for commit of subtransactions after that
* point. This should not happen anyway. Code calling this would
* typically have called BeginInternalSubTransaction() first, failing
* there.
*/
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot commit subtransactions during a parallel operation")));
if (s->blockState != TBLOCK_SUBINPROGRESS)
elog(ERROR, "ReleaseCurrentSubTransaction: unexpected state %s",
BlockStateAsString(s->blockState));
@ -3827,6 +4118,14 @@ RollbackAndReleaseCurrentSubTransaction(void)
{
TransactionState s = CurrentTransactionState;
/*
* Unlike ReleaseCurrentSubTransaction(), this is nominally permitted
* during parallel operations. That's because we may be in the master,
* recovering from an error thrown while we were in parallel mode. We
* won't reach here in a worker, because BeginInternalSubTransaction()
* will have failed.
*/
switch (s->blockState)
{
/* Must be in a subtransaction */
@ -3838,6 +4137,7 @@ RollbackAndReleaseCurrentSubTransaction(void)
case TBLOCK_DEFAULT:
case TBLOCK_STARTED:
case TBLOCK_BEGIN:
case TBLOCK_PARALLEL_INPROGRESS:
case TBLOCK_SUBBEGIN:
case TBLOCK_INPROGRESS:
case TBLOCK_END:
@ -3913,6 +4213,7 @@ AbortOutOfAnyTransaction(void)
case TBLOCK_STARTED:
case TBLOCK_BEGIN:
case TBLOCK_INPROGRESS:
case TBLOCK_PARALLEL_INPROGRESS:
case TBLOCK_END:
case TBLOCK_ABORT_PENDING:
case TBLOCK_PREPARE:
@ -4004,6 +4305,7 @@ TransactionBlockStatusCode(void)
case TBLOCK_BEGIN:
case TBLOCK_SUBBEGIN:
case TBLOCK_INPROGRESS:
case TBLOCK_PARALLEL_INPROGRESS:
case TBLOCK_SUBINPROGRESS:
case TBLOCK_END:
case TBLOCK_SUBRELEASE:
@ -4107,6 +4409,13 @@ CommitSubTransaction(void)
CallSubXactCallbacks(SUBXACT_EVENT_PRE_COMMIT_SUB, s->subTransactionId,
s->parent->subTransactionId);
/* If in parallel mode, clean up workers and exit parallel mode. */
if (IsInParallelMode())
{
AtEOSubXact_Parallel(true, s->subTransactionId);
s->parallelModeLevel = 0;
}
/* Do the actual "commit", such as it is */
s->state = TRANS_COMMIT;
@ -4260,6 +4569,13 @@ AbortSubTransaction(void)
*/
SetUserIdAndSecContext(s->prevUser, s->prevSecContext);
/* Exit from parallel mode, if necessary. */
if (IsInParallelMode())
{
AtEOSubXact_Parallel(false, s->subTransactionId);
s->parallelModeLevel = 0;
}
/*
* We can skip all this stuff if the subxact failed before creating a
* ResourceOwner...
@ -4400,6 +4716,7 @@ PushTransaction(void)
s->blockState = TBLOCK_SUBBEGIN;
GetUserIdAndSecContext(&s->prevUser, &s->prevSecContext);
s->prevXactReadOnly = XactReadOnly;
s->parallelModeLevel = 0;
CurrentTransactionState = s;
@ -4446,6 +4763,139 @@ PopTransaction(void)
pfree(s);
}
/*
* EstimateTransactionStateSpace
* Estimate the amount of space that will be needed by
* SerializeTransactionState. It would be OK to overestimate slightly,
* but it's simple for us to work out the precise value, so we do.
*/
Size
EstimateTransactionStateSpace(void)
{
TransactionState s;
Size nxids = 5; /* iso level, deferrable, top & current XID, XID count */
for (s = CurrentTransactionState; s != NULL; s = s->parent)
{
if (TransactionIdIsValid(s->transactionId))
nxids = add_size(nxids, 1);
nxids = add_size(nxids, s->nChildXids);
}
nxids = add_size(nxids, nParallelCurrentXids);
return mul_size(nxids, sizeof(TransactionId));
}
/*
* SerializeTransactionState
* Write out relevant details of our transaction state that will be
* needed by a parallel worker.
*
* We need to save and restore XactDeferrable, XactIsoLevel, and the XIDs
* associated with this transaction. The first eight bytes of the result
* contain XactDeferrable and XactIsoLevel; the next eight bytes contain the
* XID of the top-level transaction and the XID of the current transaction
* (or, in each case, InvalidTransactionId if none). After that, the next 4
* bytes contain a count of how many additional XIDs follow; this is followed
* by all of those XIDs one after another. We emit the XIDs in sorted order
* for the convenience of the receiving process.
*/
void
SerializeTransactionState(Size maxsize, char *start_address)
{
TransactionState s;
Size nxids = 0;
Size i = 0;
TransactionId *workspace;
TransactionId *result = (TransactionId *) start_address;
Assert(maxsize >= 5 * sizeof(TransactionId));
result[0] = (TransactionId) XactIsoLevel;
result[1] = (TransactionId) XactDeferrable;
result[2] = XactTopTransactionId;
result[3] = CurrentTransactionState->transactionId;
/*
* If we're running in a parallel worker and launching a parallel worker
* of our own, we can just pass along the information that was passed to
* us.
*/
if (nParallelCurrentXids > 0)
{
Assert(maxsize > (nParallelCurrentXids + 4) * sizeof(TransactionId));
result[4] = nParallelCurrentXids;
memcpy(&result[5], ParallelCurrentXids,
nParallelCurrentXids * sizeof(TransactionId));
return;
}
/*
* OK, we need to generate a sorted list of XIDs that our workers
* should view as current. First, figure out how many there are.
*/
for (s = CurrentTransactionState; s != NULL; s = s->parent)
{
if (TransactionIdIsValid(s->transactionId))
nxids = add_size(nxids, 1);
nxids = add_size(nxids, s->nChildXids);
}
Assert(nxids * sizeof(TransactionId) < maxsize);
/* Copy them to our scratch space. */
workspace = palloc(nxids * sizeof(TransactionId));
for (s = CurrentTransactionState; s != NULL; s = s->parent)
{
if (TransactionIdIsValid(s->transactionId))
workspace[i++] = s->transactionId;
memcpy(&workspace[i], s->childXids,
s->nChildXids * sizeof(TransactionId));
i += s->nChildXids;
}
Assert(i == nxids);
/* Sort them. */
qsort(workspace, nxids, sizeof(TransactionId), xidComparator);
/* Copy data into output area. */
result[4] = (TransactionId) nxids;
memcpy(&result[5], workspace, nxids * sizeof(TransactionId));
}
/*
* StartParallelWorkerTransaction
* Start a parallel worker transaction, restoring the relevant
* transaction state serialized by SerializeTransactionState.
*/
void
StartParallelWorkerTransaction(char *tstatespace)
{
TransactionId *tstate = (TransactionId *) tstatespace;
Assert(CurrentTransactionState->blockState == TBLOCK_DEFAULT);
StartTransaction();
XactIsoLevel = (int) tstate[0];
XactDeferrable = (bool) tstate[1];
XactTopTransactionId = tstate[2];
CurrentTransactionState->transactionId = tstate[3];
nParallelCurrentXids = (int) tstate[4];
ParallelCurrentXids = &tstate[5];
CurrentTransactionState->blockState = TBLOCK_PARALLEL_INPROGRESS;
}
/*
* EndParallelWorkerTransaction
* End a parallel worker transaction.
*/
void
EndParallelWorkerTransaction(void)
{
Assert(CurrentTransactionState->blockState == TBLOCK_PARALLEL_INPROGRESS);
CommitTransaction();
CurrentTransactionState->blockState = TBLOCK_DEFAULT;
}
/*
* ShowTransactionState
* Debug support
@ -4516,6 +4966,8 @@ BlockStateAsString(TBlockState blockState)
return "BEGIN";
case TBLOCK_INPROGRESS:
return "INPROGRESS";
case TBLOCK_PARALLEL_INPROGRESS:
return "PARALLEL_INPROGRESS";
case TBLOCK_END:
return "END";
case TBLOCK_ABORT:

8
src/backend/access/transam/xlog.c
View file

@ -292,6 +292,14 @@ static TimeLineID curFileTLI;
* end+1 of the last record, and is reset when we end a top-level transaction,
* or start a new one; so it can be used to tell if the current transaction has
* created any XLOG records.
*
* While in parallel mode, this may not be fully up to date. When committing,
* a transaction can assume this covers all xlog records written either by the
* user backend or by any parallel worker which was present at any point during
* the transaction. But when aborting, or when still in parallel mode, other
* parallel backends may have written WAL records at later LSNs than the value
* stored here. The parallel leader advances its own copy, when necessary,
* in WaitForParallelWorkersToFinish.
*/
static XLogRecPtr ProcLastRecPtr = InvalidXLogRecPtr;

11
src/backend/catalog/namespace.c
View file

@ -20,6 +20,7 @@
#include "postgres.h"
#include "access/htup_details.h"
#include "access/parallel.h"
#include "access/xact.h"
#include "access/xlog.h"
#include "catalog/dependency.h"
@ -3646,6 +3647,12 @@ InitTempTableNamespace(void)
(errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
errmsg("cannot create temporary tables during recovery")));
/* Parallel workers can't create temporary tables, either. */
if (IsParallelWorker())
ereport(ERROR,
(errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
errmsg("cannot create temporary tables in parallel mode")));
snprintf(namespaceName, sizeof(namespaceName), "pg_temp_%d", MyBackendId);
namespaceId = get_namespace_oid(namespaceName, true);
@ -3709,7 +3716,7 @@ InitTempTableNamespace(void)
* End-of-transaction cleanup for namespaces.
*/
void
AtEOXact_Namespace(bool isCommit)
AtEOXact_Namespace(bool isCommit, bool parallel)
{
/*
* If we abort the transaction in which a temp namespace was selected,
@ -3719,7 +3726,7 @@ AtEOXact_Namespace(bool isCommit)
* at backend shutdown. (We only want to register the callback once per
* session, so this is a good place to do it.)
*/
if (myTempNamespaceSubID != InvalidSubTransactionId)
if (myTempNamespaceSubID != InvalidSubTransactionId && !parallel)
{
if (isCommit)
before_shmem_exit(RemoveTempRelationsCallback, 0);

3
src/backend/commands/copy.c
View file

@ -924,9 +924,10 @@ DoCopy(const CopyStmt *stmt, const char *queryString, uint64 *processed)
{
Assert(rel);
/* check read-only transaction */
/* check read-only transaction and parallel mode */
if (XactReadOnly && !rel->rd_islocaltemp)
PreventCommandIfReadOnly("COPY FROM");
PreventCommandIfParallelMode("COPY FROM");
cstate = BeginCopyFrom(rel, stmt->filename, stmt->is_program,
stmt->attlist, stmt->options);

14
src/backend/commands/sequence.c
View file

@ -565,6 +565,13 @@ nextval_internal(Oid relid)
if (!seqrel->rd_islocaltemp)
PreventCommandIfReadOnly("nextval()");
/*
* Forbid this during parallel operation because, to make it work,
* the cooperating backends would need to share the backend-local cached
* sequence information. Currently, we don't support that.
*/
PreventCommandIfParallelMode("nextval()");
if (elm->last != elm->cached) /* some numbers were cached */
{
Assert(elm->last_valid);
@ -862,6 +869,13 @@ do_setval(Oid relid, int64 next, bool iscalled)
if (!seqrel->rd_islocaltemp)
PreventCommandIfReadOnly("setval()");
/*
* Forbid this during parallel operation because, to make it work,
* the cooperating backends would need to share the backend-local cached
* sequence information. Currently, we don't support that.
*/
PreventCommandIfParallelMode("setval()");
/* lock page' buffer and read tuple */
seq = read_seq_tuple(elm, seqrel, &buf, &seqtuple);

30
src/backend/executor/execMain.c
View file

@ -147,8 +147,20 @@ standard_ExecutorStart(QueryDesc *queryDesc, int eflags)
/*
* If the transaction is read-only, we need to check if any writes are
* planned to non-temporary tables. EXPLAIN is considered read-only.
*
* Don't allow writes in parallel mode. Supporting UPDATE and DELETE would
* require (a) storing the combocid hash in shared memory, rather than
* synchronizing it just once at the start of parallelism, and (b) an
* alternative to heap_update()'s reliance on xmax for mutual exclusion.
* INSERT may have no such troubles, but we forbid it to simplify the
* checks.
*
* We have lower-level defenses in CommandCounterIncrement and elsewhere
* against performing unsafe operations in parallel mode, but this gives
* a more user-friendly error message.
*/
if (XactReadOnly && !(eflags & EXEC_FLAG_EXPLAIN_ONLY))
if ((XactReadOnly || IsInParallelMode()) &&
!(eflags & EXEC_FLAG_EXPLAIN_ONLY))
ExecCheckXactReadOnly(queryDesc->plannedstmt);
/*
@ -691,18 +703,23 @@ ExecCheckRTEPerms(RangeTblEntry *rte)
}
/*
* Check that the query does not imply any writes to non-temp tables.
* Check that the query does not imply any writes to non-temp tables;
* unless we're in parallel mode, in which case don't even allow writes
* to temp tables.
*
* Note: in a Hot Standby slave this would need to reject writes to temp
* tables as well; but an HS slave can't have created any temp tables
* in the first place, so no need to check that.
* tables just as we do in parallel mode; but an HS slave can't have created
* any temp tables in the first place, so no need to check that.
*/
static void
ExecCheckXactReadOnly(PlannedStmt *plannedstmt)
{
ListCell *l;
/* Fail if write permissions are requested on any non-temp table */
/*
* Fail if write permissions are requested in parallel mode for
* table (temp or non-temp), otherwise fail for any non-temp table.
*/
foreach(l, plannedstmt->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
@ -718,6 +735,9 @@ ExecCheckXactReadOnly(PlannedStmt *plannedstmt)
PreventCommandIfReadOnly(CreateCommandTag((Node *) plannedstmt));
}
if (plannedstmt->commandType != CMD_SELECT || plannedstmt->hasModifyingCTE)
PreventCommandIfParallelMode(CreateCommandTag((Node *) plannedstmt));
}

3
src/backend/executor/functions.c
View file

@ -513,6 +513,9 @@ init_execution_state(List *queryTree_list,
errmsg("%s is not allowed in a non-volatile function",
CreateCommandTag(stmt))));
if (IsInParallelMode() && !CommandIsReadOnly(stmt))
PreventCommandIfParallelMode(CreateCommandTag(stmt));
/* OK, build the execution_state for this query */
newes = (execution_state *) palloc(sizeof(execution_state));
if (preves)

32
src/backend/executor/spi.c
View file

@ -23,6 +23,7 @@
#include "commands/trigger.h"
#include "executor/executor.h"
#include "executor/spi_priv.h"
#include "miscadmin.h"
#include "tcop/pquery.h"
#include "tcop/utility.h"
#include "utils/builtins.h"
@ -1322,13 +1323,14 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
}
/*
* If told to be read-only, we'd better check for read-only queries. This
* can't be done earlier because we need to look at the finished, planned
* queries. (In particular, we don't want to do it between GetCachedPlan
* and PortalDefineQuery, because throwing an error between those steps
* would result in leaking our plancache refcount.)
* If told to be read-only, or in parallel mode, verify that this query
* is in fact read-only. This can't be done earlier because we need to
* look at the finished, planned queries. (In particular, we don't want
* to do it between GetCachedPlan and PortalDefineQuery, because throwing
* an error between those steps would result in leaking our plancache
* refcount.)
*/
if (read_only)
if (read_only || IsInParallelMode())
{
ListCell *lc;
@ -1337,11 +1339,16 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
Node *pstmt = (Node *) lfirst(lc);
if (!CommandIsReadOnly(pstmt))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/* translator: %s is a SQL statement name */
errmsg("%s is not allowed in a non-volatile function",
CreateCommandTag(pstmt))));
{
if (read_only)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/* translator: %s is a SQL statement name */
errmsg("%s is not allowed in a non-volatile function",
CreateCommandTag(pstmt))));
else
PreventCommandIfParallelMode(CreateCommandTag(pstmt));
}
}
}
@ -2129,6 +2136,9 @@ _SPI_execute_plan(SPIPlanPtr plan, ParamListInfo paramLI,
errmsg("%s is not allowed in a non-volatile function",
CreateCommandTag(stmt))));
if (IsInParallelMode() && !CommandIsReadOnly(stmt))
PreventCommandIfParallelMode(CreateCommandTag(stmt));
/*
* If not read-only mode, advance the command counter before each
* command and update the snapshot.

33
src/backend/libpq/pqmq.c
View file

@ -16,12 +16,15 @@
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "libpq/pqmq.h"
#include "miscadmin.h"
#include "tcop/tcopprot.h"
#include "utils/builtins.h"
static shm_mq *pq_mq;
static shm_mq_handle *pq_mq_handle;
static bool pq_mq_busy = false;
static pid_t pq_mq_parallel_master_pid = 0;
static pid_t pq_mq_parallel_master_backend_id = InvalidBackendId;
static void mq_comm_reset(void);
static int mq_flush(void);
@ -57,6 +60,18 @@ pq_redirect_to_shm_mq(shm_mq *mq, shm_mq_handle *mqh)
FrontendProtocol = PG_PROTOCOL_LATEST;
}
/*
* Arrange to SendProcSignal() to the parallel master each time we transmit
* message data via the shm_mq.
*/
void
pq_set_parallel_master(pid_t pid, BackendId backend_id)
{
Assert(PqCommMethods == &PqCommMqMethods);
pq_mq_parallel_master_pid = pid;
pq_mq_parallel_master_backend_id = backend_id;
}
static void
mq_comm_reset(void)
{
@ -120,7 +135,23 @@ mq_putmessage(char msgtype, const char *s, size_t len)
iov[1].len = len;
Assert(pq_mq_handle != NULL);
result = shm_mq_sendv(pq_mq_handle, iov, 2, false);
for (;;)
{
result = shm_mq_sendv(pq_mq_handle, iov, 2, true);
if (pq_mq_parallel_master_pid != 0)
SendProcSignal(pq_mq_parallel_master_pid,
PROCSIG_PARALLEL_MESSAGE,
pq_mq_parallel_master_backend_id);
if (result != SHM_MQ_WOULD_BLOCK)
break;
WaitLatch(&MyProc->procLatch, WL_LATCH_SET, 0);
CHECK_FOR_INTERRUPTS();
ResetLatch(&MyProc->procLatch);
}
pq_mq_busy = false;

50
src/backend/postmaster/bgworker.c
View file

@ -995,6 +995,56 @@ WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pidp)
return status;
}
/*
* Wait for a background worker to stop.
*
* If the worker hasn't yet started, or is running, we wait for it to stop
* and then return BGWH_STOPPED. However, if the postmaster has died, we give
* up and return BGWH_POSTMASTER_DIED, because it's the postmaster that
* notifies us when a worker's state changes.
*/
BgwHandleStatus
WaitForBackgroundWorkerShutdown(BackgroundWorkerHandle *handle)
{
BgwHandleStatus status;
int rc;
bool save_set_latch_on_sigusr1;
save_set_latch_on_sigusr1 = set_latch_on_sigusr1;
set_latch_on_sigusr1 = true;
PG_TRY();
{
for (;;)
{
pid_t pid;
CHECK_FOR_INTERRUPTS();
status = GetBackgroundWorkerPid(handle, &pid);
if (status == BGWH_STOPPED)
return status;
rc = WaitLatch(&MyProc->procLatch,
WL_LATCH_SET | WL_POSTMASTER_DEATH, 0);
if (rc & WL_POSTMASTER_DEATH)
return BGWH_POSTMASTER_DIED;
ResetLatch(&MyProc->procLatch);
}
}
PG_CATCH();
{
set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
PG_RE_THROW();
}
PG_END_TRY();
set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
return status;
}
/*
* Instruct the postmaster to terminate a background worker.
*

44
src/backend/storage/ipc/procarray.c
View file

@ -1682,6 +1682,50 @@ ProcArrayInstallImportedXmin(TransactionId xmin, TransactionId sourcexid)
return result;
}
/*
* ProcArrayInstallRestoredXmin -- install restored xmin into MyPgXact->xmin
*
* This is like ProcArrayInstallImportedXmin, but we have a pointer to the
* PGPROC of the transaction from which we imported the snapshot, rather than
* an XID.
*
* Returns TRUE if successful, FALSE if source xact is no longer running.
*/
bool
ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc)
{
bool result = false;
TransactionId xid;
volatile PGXACT *pgxact;
Assert(TransactionIdIsNormal(xmin));
Assert(proc != NULL);
/* Get lock so source xact can't end while we're doing this */
LWLockAcquire(ProcArrayLock, LW_SHARED);
pgxact = &allPgXact[proc->pgprocno];
/*
* Be certain that the referenced PGPROC has an advertised xmin which
* is no later than the one we're installing, so that the system-wide
* xmin can't go backwards. Also, make sure it's running in the same
* database, so that the per-database xmin cannot go backwards.
*/
xid = pgxact->xmin; /* fetch just once */
if (proc->databaseId == MyDatabaseId &&
TransactionIdIsNormal(xid) &&
TransactionIdPrecedesOrEquals(xid, xmin))
{
MyPgXact->xmin = TransactionXmin = xmin;
result = true;
}
LWLockRelease(ProcArrayLock);
return result;
}
/*
* GetRunningTransactionData -- returns information about running transactions.
*

4
src/backend/storage/ipc/procsignal.c
View file

@ -17,6 +17,7 @@
#include <signal.h>
#include <unistd.h>
#include "access/parallel.h"
#include "commands/async.h"
#include "miscadmin.h"
#include "storage/latch.h"
@ -274,6 +275,9 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
if (CheckProcSignal(PROCSIG_NOTIFY_INTERRUPT))
HandleNotifyInterrupt();
if (CheckProcSignal(PROCSIG_PARALLEL_MESSAGE))
HandleParallelMessageInterrupt();
if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_DATABASE))
RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_DATABASE);

8
src/backend/storage/lmgr/predicate.c
View file

@ -1653,6 +1653,14 @@ GetSerializableTransactionSnapshotInt(Snapshot snapshot,
Assert(!RecoveryInProgress());
/*
* Since all parts of a serializable transaction must use the same
* snapshot, it is too late to establish one after a parallel operation
* has begun.
*/
if (IsInParallelMode())
elog(ERROR, "cannot establish serializable snapshot during a parallel operation");
proc = MyProc;
Assert(proc != NULL);
GET_VXID_FROM_PGPROC(vxid, *proc);

4
src/backend/tcop/postgres.c
View file

@ -36,6 +36,7 @@
#include "rusagestub.h"
#endif
#include "access/parallel.h"
#include "access/printtup.h"
#include "access/xact.h"
#include "catalog/pg_type.h"
@ -2988,7 +2989,8 @@ ProcessInterrupts(void)
}
}
/* If we get here, do nothing (probably, QueryCancelPending was reset) */
if (ParallelMessagePending)
HandleParallelMessages();
}

30
src/backend/tcop/utility.c
View file

@ -128,14 +128,15 @@ CommandIsReadOnly(Node *parsetree)
static void
check_xact_readonly(Node *parsetree)
{
if (!XactReadOnly)
/* Only perform the check if we have a reason to do so. */
if (!XactReadOnly && !IsInParallelMode())
return;
/*
* Note: Commands that need to do more complicated checking are handled
* elsewhere, in particular COPY and plannable statements do their own
* checking. However they should all call PreventCommandIfReadOnly to
* actually throw the error.
* checking. However they should all call PreventCommandIfReadOnly
* or PreventCommandIfParallelMode to actually throw the error.
*/
switch (nodeTag(parsetree))
@ -208,6 +209,7 @@ check_xact_readonly(Node *parsetree)
case T_ImportForeignSchemaStmt:
case T_SecLabelStmt:
PreventCommandIfReadOnly(CreateCommandTag(parsetree));
PreventCommandIfParallelMode(CreateCommandTag(parsetree));
break;
default:
/* do nothing */
@ -232,6 +234,24 @@ PreventCommandIfReadOnly(const char *cmdname)
cmdname)));
}
/*
* PreventCommandIfParallelMode: throw error if current (sub)transaction is
* in parallel mode.
*
* This is useful mainly to ensure consistency of the error message wording;
* most callers have checked IsInParallelMode() for themselves.
*/
void
PreventCommandIfParallelMode(const char *cmdname)
{
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
/* translator: %s is name of a SQL command, eg CREATE */
errmsg("cannot execute %s during a parallel operation",
cmdname)));
}
/*
* PreventCommandDuringRecovery: throw error if RecoveryInProgress
*
@ -618,6 +638,7 @@ standard_ProcessUtility(Node *parsetree,
case T_ClusterStmt:
/* we choose to allow this during "read only" transactions */
PreventCommandDuringRecovery("CLUSTER");
/* forbidden in parallel mode due to CommandIsReadOnly */
cluster((ClusterStmt *) parsetree, isTopLevel);
break;
@ -628,6 +649,7 @@ standard_ProcessUtility(Node *parsetree,
/* we choose to allow this during "read only" transactions */
PreventCommandDuringRecovery((stmt->options & VACOPT_VACUUM) ?
"VACUUM" : "ANALYZE");
/* forbidden in parallel mode due to CommandIsReadOnly */
ExecVacuum(stmt, isTopLevel);
}
break;
@ -704,6 +726,7 @@ standard_ProcessUtility(Node *parsetree,
* outside a transaction block is presumed to be user error.
*/
RequireTransactionChain(isTopLevel, "LOCK TABLE");
/* forbidden in parallel mode due to CommandIsReadOnly */
LockTableCommand((LockStmt *) parsetree);
break;
@ -735,6 +758,7 @@ standard_ProcessUtility(Node *parsetree,
/* we choose to allow this during "read only" transactions */
PreventCommandDuringRecovery("REINDEX");
/* forbidden in parallel mode due to CommandIsReadOnly */
switch (stmt->kind)
{
case REINDEX_OBJECT_INDEX:

30
src/backend/utils/adt/lockfuncs.c
View file

@ -13,6 +13,7 @@
#include "postgres.h"
#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "miscadmin.h"
@ -411,6 +412,15 @@ pg_lock_status(PG_FUNCTION_ARGS)
#define SET_LOCKTAG_INT32(tag, key1, key2) \
SET_LOCKTAG_ADVISORY(tag, MyDatabaseId, key1, key2, 2)
static void
PreventAdvisoryLocksInParallelMode(void)
{
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot use advisory locks during a parallel operation")));
}
/*
* pg_advisory_lock(int8) - acquire exclusive lock on an int8 key
*/
@ -420,6 +430,7 @@ pg_advisory_lock_int8(PG_FUNCTION_ARGS)
int64 key = PG_GETARG_INT64(0);
LOCKTAG tag;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT64(tag, key);
(void) LockAcquire(&tag, ExclusiveLock, true, false);
@ -437,6 +448,7 @@ pg_advisory_xact_lock_int8(PG_FUNCTION_ARGS)
int64 key = PG_GETARG_INT64(0);
LOCKTAG tag;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT64(tag, key);
(void) LockAcquire(&tag, ExclusiveLock, false, false);
@ -453,6 +465,7 @@ pg_advisory_lock_shared_int8(PG_FUNCTION_ARGS)
int64 key = PG_GETARG_INT64(0);
LOCKTAG tag;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT64(tag, key);
(void) LockAcquire(&tag, ShareLock, true, false);
@ -470,6 +483,7 @@ pg_advisory_xact_lock_shared_int8(PG_FUNCTION_ARGS)
int64 key = PG_GETARG_INT64(0);
LOCKTAG tag;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT64(tag, key);
(void) LockAcquire(&tag, ShareLock, false, false);
@ -489,6 +503,7 @@ pg_try_advisory_lock_int8(PG_FUNCTION_ARGS)
LOCKTAG tag;
LockAcquireResult res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT64(tag, key);
res = LockAcquire(&tag, ExclusiveLock, true, true);
@ -509,6 +524,7 @@ pg_try_advisory_xact_lock_int8(PG_FUNCTION_ARGS)
LOCKTAG tag;
LockAcquireResult res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT64(tag, key);
res = LockAcquire(&tag, ExclusiveLock, false, true);
@ -528,6 +544,7 @@ pg_try_advisory_lock_shared_int8(PG_FUNCTION_ARGS)
LOCKTAG tag;
LockAcquireResult res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT64(tag, key);
res = LockAcquire(&tag, ShareLock, true, true);
@ -548,6 +565,7 @@ pg_try_advisory_xact_lock_shared_int8(PG_FUNCTION_ARGS)
LOCKTAG tag;
LockAcquireResult res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT64(tag, key);
res = LockAcquire(&tag, ShareLock, false, true);
@ -567,6 +585,7 @@ pg_advisory_unlock_int8(PG_FUNCTION_ARGS)
LOCKTAG tag;
bool res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT64(tag, key);
res = LockRelease(&tag, ExclusiveLock, true);
@ -586,6 +605,7 @@ pg_advisory_unlock_shared_int8(PG_FUNCTION_ARGS)
LOCKTAG tag;
bool res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT64(tag, key);
res = LockRelease(&tag, ShareLock, true);
@ -603,6 +623,7 @@ pg_advisory_lock_int4(PG_FUNCTION_ARGS)
int32 key2 = PG_GETARG_INT32(1);
LOCKTAG tag;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT32(tag, key1, key2);
(void) LockAcquire(&tag, ExclusiveLock, true, false);
@ -621,6 +642,7 @@ pg_advisory_xact_lock_int4(PG_FUNCTION_ARGS)
int32 key2 = PG_GETARG_INT32(1);
LOCKTAG tag;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT32(tag, key1, key2);
(void) LockAcquire(&tag, ExclusiveLock, false, false);
@ -638,6 +660,7 @@ pg_advisory_lock_shared_int4(PG_FUNCTION_ARGS)
int32 key2 = PG_GETARG_INT32(1);
LOCKTAG tag;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT32(tag, key1, key2);
(void) LockAcquire(&tag, ShareLock, true, false);
@ -656,6 +679,7 @@ pg_advisory_xact_lock_shared_int4(PG_FUNCTION_ARGS)
int32 key2 = PG_GETARG_INT32(1);
LOCKTAG tag;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT32(tag, key1, key2);
(void) LockAcquire(&tag, ShareLock, false, false);
@ -676,6 +700,7 @@ pg_try_advisory_lock_int4(PG_FUNCTION_ARGS)
LOCKTAG tag;
LockAcquireResult res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT32(tag, key1, key2);
res = LockAcquire(&tag, ExclusiveLock, true, true);
@ -697,6 +722,7 @@ pg_try_advisory_xact_lock_int4(PG_FUNCTION_ARGS)
LOCKTAG tag;
LockAcquireResult res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT32(tag, key1, key2);
res = LockAcquire(&tag, ExclusiveLock, false, true);
@ -717,6 +743,7 @@ pg_try_advisory_lock_shared_int4(PG_FUNCTION_ARGS)
LOCKTAG tag;
LockAcquireResult res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT32(tag, key1, key2);
res = LockAcquire(&tag, ShareLock, true, true);
@ -738,6 +765,7 @@ pg_try_advisory_xact_lock_shared_int4(PG_FUNCTION_ARGS)
LOCKTAG tag;
LockAcquireResult res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT32(tag, key1, key2);
res = LockAcquire(&tag, ShareLock, false, true);
@ -758,6 +786,7 @@ pg_advisory_unlock_int4(PG_FUNCTION_ARGS)
LOCKTAG tag;
bool res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT32(tag, key1, key2);
res = LockRelease(&tag, ExclusiveLock, true);
@ -778,6 +807,7 @@ pg_advisory_unlock_shared_int4(PG_FUNCTION_ARGS)
LOCKTAG tag;
bool res;
PreventAdvisoryLocksInParallelMode();
SET_LOCKTAG_INT32(tag, key1, key2);
res = LockRelease(&tag, ShareLock, true);

54
src/backend/utils/fmgr/dfmgr.c
View file

@ -23,6 +23,7 @@
#endif
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "storage/shmem.h"
#include "utils/dynamic_loader.h"
#include "utils/hsearch.h"
@ -692,3 +693,56 @@ find_rendezvous_variable(const char *varName)
return &hentry->varValue;
}
/*
* Estimate the amount of space needed to serialize the list of libraries
* we have loaded.
*/
Size
EstimateLibraryStateSpace(void)
{
DynamicFileList *file_scanner;
Size size = 1;
for (file_scanner = file_list;
file_scanner != NULL;
file_scanner = file_scanner->next)
size = add_size(size, strlen(file_scanner->filename) + 1);
return size;
}
/*
* Serialize the list of libraries we have loaded to a chunk of memory.
*/
void
SerializeLibraryState(Size maxsize, char *start_address)
{
DynamicFileList *file_scanner;
for (file_scanner = file_list;
file_scanner != NULL;
file_scanner = file_scanner->next)
{
Size len;
len = strlcpy(start_address, file_scanner->filename, maxsize) + 1;
Assert(len < maxsize);
maxsize -= len;
start_address += len;
}
start_address[0] = '\0';
}
/*
* Load every library the serializing backend had loaded.
*/
void
RestoreLibraryState(char *start_address)
{
while (*start_address != '\0')
{
internal_load_library(start_address);
start_address += strlen(start_address) + 1;
}
}

23
src/backend/utils/misc/guc.c
View file

@ -5665,6 +5665,20 @@ set_config_option(const char *name, const char *value,
elevel = ERROR;
}
/*
* GUC_ACTION_SAVE changes are acceptable during a parallel operation,
* because the current worker will also pop the change. We're probably
* dealing with a function having a proconfig entry. Only the function's
* body should observe the change, and peer workers do not share in the
* execution of a function call started by this worker.
*
* Other changes might need to affect other workers, so forbid them.
*/
if (IsInParallelMode() && changeVal && action != GUC_ACTION_SAVE)
ereport(elevel,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot set parameters during a parallel operation")));
record = find_option(name, true, elevel);
if (record == NULL)
{
@ -6969,6 +6983,15 @@ ExecSetVariableStmt(VariableSetStmt *stmt, bool isTopLevel)
{
GucAction action = stmt->is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET;
/*
* Workers synchronize these parameters at the start of the parallel
* operation; then, we block SET during the operation.
*/
if (IsInParallelMode())
ereport(ERROR,
(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
errmsg("cannot set parameters during a parallel operation")));
switch (stmt->kind)
{
case VAR_SET_VALUE:

74
src/backend/utils/time/combocid.c
View file

@ -44,6 +44,7 @@
#include "miscadmin.h"
#include "access/htup_details.h"
#include "access/xact.h"
#include "storage/shmem.h"
#include "utils/combocid.h"
#include "utils/hsearch.h"
#include "utils/memutils.h"
@ -286,3 +287,76 @@ GetRealCmax(CommandId combocid)
Assert(combocid < usedComboCids);
return comboCids[combocid].cmax;
}
/*
* Estimate the amount of space required to serialize the current ComboCID
* state.
*/
Size
EstimateComboCIDStateSpace(void)
{
Size size;
/* Add space required for saving usedComboCids */
size = sizeof(int);
/* Add space required for saving the combocids key */
size = add_size(size, mul_size(sizeof(ComboCidKeyData), usedComboCids));
return size;
}
/*
* Serialize the ComboCID state into the memory, beginning at start_address.
* maxsize should be at least as large as the value returned by
* EstimateComboCIDStateSpace.
*/
void
SerializeComboCIDState(Size maxsize, char *start_address)
{
char *endptr;
/* First, we store the number of currently-existing ComboCIDs. */
* (int *) start_address = usedComboCids;
/* If maxsize is too small, throw an error. */
endptr = start_address + sizeof(int) +
(sizeof(ComboCidKeyData) * usedComboCids);
if (endptr < start_address || endptr > start_address + maxsize)
elog(ERROR, "not enough space to serialize ComboCID state");
/* Now, copy the actual cmin/cmax pairs. */
memcpy(start_address + sizeof(int), comboCids,
(sizeof(ComboCidKeyData) * usedComboCids));
}
/*
* Read the ComboCID state at the specified address and initialize this
* backend with the same ComboCIDs. This is only valid in a backend that
* currently has no ComboCIDs (and only makes sense if the transaction state
* is serialized and restored as well).
*/
void
RestoreComboCIDState(char *comboCIDstate)
{
int num_elements;
ComboCidKeyData *keydata;
int i;
CommandId cid;
Assert(!comboCids && !comboHash);
/* First, we retrieve the number of ComboCIDs that were serialized. */
num_elements = * (int *) comboCIDstate;
keydata = (ComboCidKeyData *) (comboCIDstate + sizeof(int));
/* Use GetComboCommandId to restore each ComboCID. */
for (i = 0; i < num_elements; i++)
{
cid = GetComboCommandId(keydata[i].cmin, keydata[i].cmax);
/* Verify that we got the expected answer. */
if (cid != i)
elog(ERROR, "unexpected command ID while restoring combo CIDs");
}
}

210
src/backend/utils/time/snapmgr.c
View file

@ -157,6 +157,22 @@ static Snapshot CopySnapshot(Snapshot snapshot);
static void FreeSnapshot(Snapshot snapshot);
static void SnapshotResetXmin(void);
/*
* Snapshot fields to be serialized.
*
* Only these fields need to be sent to the cooperating backend; the
* remaining ones can (and must) set by the receiver upon restore.
*/
typedef struct SerializedSnapshotData
{
TransactionId xmin;
TransactionId xmax;
uint32 xcnt;
int32 subxcnt;
bool suboverflowed;
bool takenDuringRecovery;
CommandId curcid;
} SerializedSnapshotData;
/*
* GetTransactionSnapshot
@ -188,6 +204,10 @@ GetTransactionSnapshot(void)
Assert(pairingheap_is_empty(&RegisteredSnapshots));
Assert(FirstXactSnapshot == NULL);
if (IsInParallelMode())
elog(ERROR,
"cannot take query snapshot during a parallel operation");
/*
* In transaction-snapshot mode, the first snapshot must live until
* end of xact regardless of what the caller does with it, so we must
@ -238,6 +258,14 @@ GetTransactionSnapshot(void)
Snapshot
GetLatestSnapshot(void)
{
/*
* We might be able to relax this, but nothing that could otherwise work
* needs it.
*/
if (IsInParallelMode())
elog(ERROR,
"cannot update SecondarySnapshot during a parallel operation");
/*
* So far there are no cases requiring support for GetLatestSnapshot()
* during logical decoding, but it wouldn't be hard to add if required.
@ -347,7 +375,8 @@ SnapshotSetCommandId(CommandId curcid)
* in GetTransactionSnapshot.
*/
static void
SetTransactionSnapshot(Snapshot sourcesnap, TransactionId sourcexid)
SetTransactionSnapshot(Snapshot sourcesnap, TransactionId sourcexid,
PGPROC *sourceproc)
{
/* Caller should have checked this already */
Assert(!FirstSnapshotSet);
@ -394,7 +423,15 @@ SetTransactionSnapshot(Snapshot sourcesnap, TransactionId sourcexid)
* doesn't seem worth contorting the logic here to avoid two calls,
* especially since it's not clear that predicate.c *must* do this.
*/
if (!ProcArrayInstallImportedXmin(CurrentSnapshot->xmin, sourcexid))
if (sourceproc != NULL)
{
if (!ProcArrayInstallRestoredXmin(CurrentSnapshot->xmin, sourceproc))
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("could not import the requested snapshot"),
errdetail("The source transaction is not running anymore.")));
}
else if (!ProcArrayInstallImportedXmin(CurrentSnapshot->xmin, sourcexid))
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("could not import the requested snapshot"),
@ -550,11 +587,24 @@ PushCopiedSnapshot(Snapshot snapshot)
void
UpdateActiveSnapshotCommandId(void)
{
CommandId save_curcid, curcid;
Assert(ActiveSnapshot != NULL);
Assert(ActiveSnapshot->as_snap->active_count == 1);
Assert(ActiveSnapshot->as_snap->regd_count == 0);
ActiveSnapshot->as_snap->curcid = GetCurrentCommandId(false);
/*
* Don't allow modification of the active snapshot during parallel
* operation. We share the snapshot to worker backends at beginning of
* parallel operation, so any change to snapshot can lead to
* inconsistencies. We have other defenses against
* CommandCounterIncrement, but there are a few places that call this
* directly, so we put an additional guard here.
*/
save_curcid = ActiveSnapshot->as_snap->curcid;
curcid = GetCurrentCommandId(false);
if (IsInParallelMode() && save_curcid != curcid)
elog(ERROR, "cannot modify commandid in active snapshot during a parallel operation");
ActiveSnapshot->as_snap->curcid = curcid;
}
/*
@ -1289,7 +1339,7 @@ ImportSnapshot(const char *idstr)
errmsg("cannot import a snapshot from a different database")));
/* OK, install the snapshot */
SetTransactionSnapshot(&snapshot, src_xid);
SetTransactionSnapshot(&snapshot, src_xid, NULL);
}
/*
@ -1393,3 +1443,155 @@ HistoricSnapshotGetTupleCids(void)
Assert(HistoricSnapshotActive());
return tuplecid_data;
}
/*
* EstimateSnapshotSpace
* Returns the size need to store the given snapshot.
*
* We are exporting only required fields from the Snapshot, stored in
* SerializedSnapshotData.
*/
Size
EstimateSnapshotSpace(Snapshot snap)
{
Size size;
Assert(snap != InvalidSnapshot);
Assert(snap->satisfies == HeapTupleSatisfiesMVCC);
/* We allocate any XID arrays needed in the same palloc block. */
size = add_size(sizeof(SerializedSnapshotData),
mul_size(snap->xcnt, sizeof(TransactionId)));
if (snap->subxcnt > 0 &&
(!snap->suboverflowed || snap->takenDuringRecovery))
size = add_size(size,
mul_size(snap->subxcnt, sizeof(TransactionId)));
return size;
}
/*
* SerializeSnapshot
* Dumps the serialized snapshot (extracted from given snapshot) onto the
* memory location at start_address.
*/
void
SerializeSnapshot(Snapshot snapshot, char *start_address)
{
SerializedSnapshotData *serialized_snapshot;
Assert(snapshot->xcnt >= 0);
Assert(snapshot->subxcnt >= 0);
serialized_snapshot = (SerializedSnapshotData *) start_address;
/* Copy all required fields */
serialized_snapshot->xmin = snapshot->xmin;
serialized_snapshot->xmax = snapshot->xmax;
serialized_snapshot->xcnt = snapshot->xcnt;
serialized_snapshot->subxcnt = snapshot->subxcnt;
serialized_snapshot->suboverflowed = snapshot->suboverflowed;
serialized_snapshot->takenDuringRecovery = snapshot->takenDuringRecovery;
serialized_snapshot->curcid = snapshot->curcid;
/*
* Ignore the SubXID array if it has overflowed, unless the snapshot
* was taken during recovey - in that case, top-level XIDs are in subxip
* as well, and we mustn't lose them.
*/
if (serialized_snapshot->suboverflowed && !snapshot->takenDuringRecovery)
serialized_snapshot->subxcnt = 0;
/* Copy XID array */
if (snapshot->xcnt > 0)
memcpy((TransactionId *) (serialized_snapshot + 1),
snapshot->xip, snapshot->xcnt * sizeof(TransactionId));
/*
* Copy SubXID array. Don't bother to copy it if it had overflowed,
* though, because it's not used anywhere in that case. Except if it's a
* snapshot taken during recovery; all the top-level XIDs are in subxip as
* well in that case, so we mustn't lose them.
*/
if (snapshot->subxcnt > 0)
{
Size subxipoff = sizeof(SerializedSnapshotData) +
snapshot->xcnt * sizeof(TransactionId);
memcpy((TransactionId *) ((char *) serialized_snapshot + subxipoff),
snapshot->subxip, snapshot->subxcnt * sizeof(TransactionId));
}
}
/*
* RestoreSnapshot
* Restore a serialized snapshot from the specified address.
*
* The copy is palloc'd in TopTransactionContext and has initial refcounts set
* to 0. The returned snapshot has the copied flag set.
*/
Snapshot
RestoreSnapshot(char *start_address)
{
SerializedSnapshotData *serialized_snapshot;
Size size;
Snapshot snapshot;
TransactionId *serialized_xids;
serialized_snapshot = (SerializedSnapshotData *) start_address;
serialized_xids = (TransactionId *)
(start_address + sizeof(SerializedSnapshotData));
/* We allocate any XID arrays needed in the same palloc block. */
size = sizeof(SnapshotData)
+ serialized_snapshot->xcnt * sizeof(TransactionId)
+ serialized_snapshot->subxcnt * sizeof(TransactionId);
/* Copy all required fields */
snapshot = (Snapshot) MemoryContextAlloc(TopTransactionContext, size);
snapshot->satisfies = HeapTupleSatisfiesMVCC;
snapshot->xmin = serialized_snapshot->xmin;
snapshot->xmax = serialized_snapshot->xmax;
snapshot->xip = NULL;
snapshot->xcnt = serialized_snapshot->xcnt;
snapshot->subxip = NULL;
snapshot->subxcnt = serialized_snapshot->subxcnt;
snapshot->suboverflowed = serialized_snapshot->suboverflowed;
snapshot->takenDuringRecovery = serialized_snapshot->takenDuringRecovery;
snapshot->curcid = serialized_snapshot->curcid;
/* Copy XIDs, if present. */
if (serialized_snapshot->xcnt > 0)
{
snapshot->xip = (TransactionId *) (snapshot + 1);
memcpy(snapshot->xip, serialized_xids,
serialized_snapshot->xcnt * sizeof(TransactionId));
}
/* Copy SubXIDs, if present. */
if (serialized_snapshot->subxcnt > 0)
{
snapshot->subxip = snapshot->xip + serialized_snapshot->xcnt;
memcpy(snapshot->subxip, serialized_xids + serialized_snapshot->xcnt,
serialized_snapshot->subxcnt * sizeof(TransactionId));
}
/* Set the copied flag so that the caller will set refcounts correctly. */
snapshot->regd_count = 0;
snapshot->active_count = 0;
snapshot->copied = true;
return snapshot;
}
/*
* Install a restored snapshot as the transaction snapshot.
*
* The second argument is of type void * so that snapmgr.h need not include
* the declaration for PGPROC.
*/
void
RestoreTransactionSnapshot(Snapshot snapshot, void *master_pgproc)
{
SetTransactionSnapshot(snapshot, InvalidTransactionId, master_pgproc);
}

68
src/include/access/parallel.h Normal file
View file

@ -0,0 +1,68 @@
/*-------------------------------------------------------------------------
*
* parallel.h
* Infrastructure for launching parallel workers
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/access/parallel.h
*
*-------------------------------------------------------------------------
*/
#ifndef PARALLEL_H
#define PARALLEL_H
#include "access/xlogdefs.h"
#include "lib/ilist.h"
#include "postmaster/bgworker.h"
#include "storage/shm_mq.h"
#include "storage/shm_toc.h"
#include "utils/elog.h"
typedef void (*parallel_worker_main_type)(dsm_segment *seg, shm_toc *toc);
typedef struct ParallelWorkerInfo
{
BackgroundWorkerHandle *bgwhandle;
shm_mq_handle *error_mqh;
int32 pid;
} ParallelWorkerInfo;
typedef struct ParallelContext
{
dlist_node node;
SubTransactionId subid;
int nworkers;
parallel_worker_main_type entrypoint;
char *library_name;
char *function_name;
ErrorContextCallback *error_context_stack;
shm_toc_estimator estimator;
dsm_segment *seg;
void *private;
shm_toc *toc;
ParallelWorkerInfo *worker;
} ParallelContext;
extern bool ParallelMessagePending;
extern int ParallelWorkerNumber;
#define IsParallelWorker() (ParallelWorkerNumber >= 0)
extern ParallelContext *CreateParallelContext(parallel_worker_main_type entrypoint, int nworkers);
extern ParallelContext *CreateParallelContextForExternalFunction(char *library_name, char *function_name, int nworkers);
extern void InitializeParallelDSM(ParallelContext *);
extern void LaunchParallelWorkers(ParallelContext *);
extern void WaitForParallelWorkersToFinish(ParallelContext *);
extern void DestroyParallelContext(ParallelContext *);
extern bool ParallelContextActive(void);
extern void HandleParallelMessageInterrupt(void);
extern void HandleParallelMessages(void);
extern void AtEOXact_Parallel(bool isCommit);
extern void AtEOSubXact_Parallel(bool isCommit, SubTransactionId mySubId);
extern void ParallelWorkerReportLastRecEnd(XLogRecPtr);
#endif /* PARALLEL_H */

11
src/include/access/xact.h
View file

@ -78,9 +78,12 @@ extern bool MyXactAccessedTempRel;
typedef enum
{
XACT_EVENT_COMMIT,
XACT_EVENT_PARALLEL_COMMIT,
XACT_EVENT_ABORT,
XACT_EVENT_PARALLEL_ABORT,
XACT_EVENT_PREPARE,
XACT_EVENT_PRE_COMMIT,
XACT_EVENT_PARALLEL_PRE_COMMIT,
XACT_EVENT_PRE_PREPARE
} XactEvent;
@ -332,6 +335,10 @@ extern void BeginInternalSubTransaction(char *name);
extern void ReleaseCurrentSubTransaction(void);
extern void RollbackAndReleaseCurrentSubTransaction(void);
extern bool IsSubTransaction(void);
extern Size EstimateTransactionStateSpace(void);
extern void SerializeTransactionState(Size maxsize, char *start_address);
extern void StartParallelWorkerTransaction(char *tstatespace);
extern void EndParallelWorkerTransaction(void);
extern bool IsTransactionBlock(void);
extern bool IsTransactionOrTransactionBlock(void);
extern char TransactionBlockStatusCode(void);
@ -368,4 +375,8 @@ extern const char *xact_identify(uint8 info);
extern void ParseCommitRecord(uint8 info, xl_xact_commit *xlrec, xl_xact_parsed_commit *parsed);
extern void ParseAbortRecord(uint8 info, xl_xact_abort *xlrec, xl_xact_parsed_abort *parsed);
extern void EnterParallelMode(void);
extern void ExitParallelMode(void);
extern bool IsInParallelMode(void);
#endif /* XACT_H */

2
src/include/catalog/namespace.h
View file

@ -140,7 +140,7 @@ extern Oid FindDefaultConversionProc(int32 for_encoding, int32 to_encoding);
/* initialization & transaction cleanup code */
extern void InitializeSearchPath(void);
extern void AtEOXact_Namespace(bool isCommit);
extern void AtEOXact_Namespace(bool isCommit, bool parallel);
extern void AtEOSubXact_Namespace(bool isCommit, SubTransactionId mySubid,
SubTransactionId parentSubid);

3
src/include/fmgr.h
View file

@ -642,6 +642,9 @@ extern PGFunction load_external_function(char *filename, char *funcname,
extern PGFunction lookup_external_function(void *filehandle, char *funcname);
extern void load_file(const char *filename, bool restricted);
extern void **find_rendezvous_variable(const char *varName);
extern Size EstimateLibraryStateSpace(void);
extern void SerializeLibraryState(Size maxsize, char *start_address);
extern void RestoreLibraryState(char *start_address);
/*
* Support for aggregate functions

1
src/include/libpq/pqmq.h
View file

@ -17,6 +17,7 @@
#include "storage/shm_mq.h"
extern void pq_redirect_to_shm_mq(shm_mq *, shm_mq_handle *);
extern void pq_set_parallel_master(pid_t pid, BackendId backend_id);
extern void pq_parse_errornotice(StringInfo str, ErrorData *edata);

1
src/include/miscadmin.h
View file

@ -271,6 +271,7 @@ extern void check_stack_depth(void);
/* in tcop/utility.c */
extern void PreventCommandIfReadOnly(const char *cmdname);
extern void PreventCommandIfParallelMode(const char *cmdname);
extern void PreventCommandDuringRecovery(const char *cmdname);
/* in utils/misc/guc.c */

2
src/include/postmaster/bgworker.h
View file

@ -112,6 +112,8 @@ extern BgwHandleStatus GetBackgroundWorkerPid(BackgroundWorkerHandle *handle,
extern BgwHandleStatus
WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *
handle, pid_t *pid);
extern BgwHandleStatus
WaitForBackgroundWorkerShutdown(BackgroundWorkerHandle *);
/* Terminate a bgworker */
extern void TerminateBackgroundWorker(BackgroundWorkerHandle *handle);

1
src/include/storage/procarray.h
View file

@ -46,6 +46,7 @@ extern Snapshot GetSnapshotData(Snapshot snapshot);
extern bool ProcArrayInstallImportedXmin(TransactionId xmin,
TransactionId sourcexid);
extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc);
extern RunningTransactions GetRunningTransactionData(void);

1
src/include/storage/procsignal.h
View file

@ -31,6 +31,7 @@ typedef enum
{
PROCSIG_CATCHUP_INTERRUPT, /* sinval catchup interrupt */
PROCSIG_NOTIFY_INTERRUPT, /* listen/notify interrupt */
PROCSIG_PARALLEL_MESSAGE, /* message from cooperating parallel backend */
/* Recovery conflict reasons */
PROCSIG_RECOVERY_CONFLICT_DATABASE,

3
src/include/utils/combocid.h
View file

@ -21,5 +21,8 @@
*/
extern void AtEOXact_ComboCid(void);
extern void RestoreComboCIDState(char *comboCIDstate);
extern void SerializeComboCIDState(Size maxsize, char *start_address);
extern Size EstimateComboCIDStateSpace(void);
#endif /* COMBOCID_H */

5
src/include/utils/snapmgr.h
View file

@ -64,4 +64,9 @@ extern void SetupHistoricSnapshot(Snapshot snapshot_now, struct HTAB *tuplecids)
extern void TeardownHistoricSnapshot(bool is_error);
extern bool HistoricSnapshotActive(void);
extern Size EstimateSnapshotSpace(Snapshot snapshot);
extern void SerializeSnapshot(Snapshot snapshot, char *start_address);
extern Snapshot RestoreSnapshot(char *start_address);
extern void RestoreTransactionSnapshot(Snapshot snapshot, void *master_pgproc);
#endif /* SNAPMGR_H */