parallel.h File Reference

#include "access/xlogdefs.h"
#include "lib/ilist.h"
#include "postmaster/bgworker.h"
#include "storage/shm_mq.h"
#include "storage/shm_toc.h"

Include dependency graph for parallel.h:

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Go to the source code of this file.

Data Structures
struct	ParallelWorkerInfo
struct	ParallelContext
struct	ParallelWorkerContext

Macros
#define	IsParallelWorker()   (ParallelWorkerNumber >= 0)

Typedefs
typedef void(*	parallel_worker_main_type) (dsm_segment *seg, shm_toc *toc)
typedef struct ParallelWorkerInfo	ParallelWorkerInfo
typedef struct ParallelContext	ParallelContext
typedef struct ParallelWorkerContext	ParallelWorkerContext

Functions
ParallelContext *	CreateParallelContext (const char *library_name, const char *function_name, int nworkers)
void	InitializeParallelDSM (ParallelContext *pcxt)
void	ReinitializeParallelDSM (ParallelContext *pcxt)
void	ReinitializeParallelWorkers (ParallelContext *pcxt, int nworkers_to_launch)
void	LaunchParallelWorkers (ParallelContext *pcxt)
void	WaitForParallelWorkersToAttach (ParallelContext *pcxt)
void	WaitForParallelWorkersToFinish (ParallelContext *pcxt)
void	DestroyParallelContext (ParallelContext *pcxt)
bool	ParallelContextActive (void)
void	HandleParallelMessageInterrupt (void)
void	ProcessParallelMessages (void)
void	AtEOXact_Parallel (bool isCommit)
void	AtEOSubXact_Parallel (bool isCommit, SubTransactionId mySubId)
void	ParallelWorkerReportLastRecEnd (XLogRecPtr last_xlog_end)
void	ParallelWorkerMain (Datum main_arg)

Variables
PGDLLIMPORT volatile sig_atomic_t	ParallelMessagePending
PGDLLIMPORT int	ParallelWorkerNumber
PGDLLIMPORT bool	InitializingParallelWorker

Macro Definition Documentation

IsParallelWorker

#define IsParallelWorker

(

)

(ParallelWorkerNumber >= 0)

Definition at line 60 of file parallel.h.

Typedef Documentation

parallel_worker_main_type

typedef void(* parallel_worker_main_type) (dsm_segment *seg, shm_toc *toc)

Definition at line 23 of file parallel.h.

ParallelContext

typedef struct ParallelContext ParallelContext

ParallelWorkerContext

typedef struct ParallelWorkerContext ParallelWorkerContext

ParallelWorkerInfo

typedef struct ParallelWorkerInfo ParallelWorkerInfo

Function Documentation

AtEOSubXact_Parallel()

void AtEOSubXact_Parallel	(	bool	isCommit,
		SubTransactionId	mySubId
	)

Definition at line 1261 of file parallel.c.

{
    while (!dlist_is_empty(&pcxt_list))
    {
        ParallelContext *pcxt;
 
        pcxt = dlist_head_element(ParallelContext, node, &pcxt_list);
        if (pcxt->subid != mySubId)
            break;
        if (isCommit)
            elog(WARNING, "leaked parallel context");
        DestroyParallelContext(pcxt);
    }
}

References DestroyParallelContext(), dlist_head_element, dlist_is_empty(), elog, pcxt_list, ParallelContext::subid, and WARNING.

Referenced by AbortSubTransaction(), and CommitSubTransaction().

AtEOXact_Parallel()

void AtEOXact_Parallel

(

bool

isCommit

)

Definition at line 1282 of file parallel.c.

{
    while (!dlist_is_empty(&pcxt_list))
    {
        ParallelContext *pcxt;
 
        pcxt = dlist_head_element(ParallelContext, node, &pcxt_list);
        if (isCommit)
            elog(WARNING, "leaked parallel context");
        DestroyParallelContext(pcxt);
    }
}

References DestroyParallelContext(), dlist_head_element, dlist_is_empty(), elog, pcxt_list, and WARNING.

Referenced by AbortTransaction(), and CommitTransaction().

CreateParallelContext()

ParallelContext * CreateParallelContext	(	const char *	library_name,
		const char *	function_name,
		int	nworkers
	)

Definition at line 173 of file parallel.c.

{
    MemoryContext oldcontext;
    ParallelContext *pcxt;
 
    /* It is unsafe to create a parallel context if not in parallel mode. */
    Assert(IsInParallelMode());
 
    /* Number of workers should be non-negative. */
    Assert(nworkers >= 0);
 
    /* We might be running in a short-lived memory context. */
    oldcontext = MemoryContextSwitchTo(TopTransactionContext);
 
    /* Initialize a new ParallelContext. */
    pcxt = palloc0_object(ParallelContext);
    pcxt->subid = GetCurrentSubTransactionId();
    pcxt->nworkers = nworkers;
    pcxt->nworkers_to_launch = nworkers;
    pcxt->library_name = pstrdup(library_name);
    pcxt->function_name = pstrdup(function_name);
    pcxt->error_context_stack = error_context_stack;
    shm_toc_initialize_estimator(&pcxt->estimator);
    dlist_push_head(&pcxt_list, &pcxt->node);
 
    /* Restore previous memory context. */
    MemoryContextSwitchTo(oldcontext);
 
    return pcxt;
}

References Assert(), dlist_push_head(), error_context_stack, ParallelContext::error_context_stack, ParallelContext::estimator, ParallelContext::function_name, GetCurrentSubTransactionId(), IsInParallelMode(), ParallelContext::library_name, MemoryContextSwitchTo(), ParallelContext::node, ParallelContext::nworkers, ParallelContext::nworkers_to_launch, palloc0_object, pcxt_list, pstrdup(), shm_toc_initialize_estimator, ParallelContext::subid, and TopTransactionContext.

Referenced by _brin_begin_parallel(), _bt_begin_parallel(), _gin_begin_parallel(), ExecInitParallelPlan(), and parallel_vacuum_init().

DestroyParallelContext()

void DestroyParallelContext

(

ParallelContext *

pcxt

)

Definition at line 957 of file parallel.c.

{
    int         i;
 
    /*
     * Be careful about order of operations here!  We remove the parallel
     * context from the list before we do anything else; otherwise, if an
     * error occurs during a subsequent step, we might try to nuke it again
     * from AtEOXact_Parallel or AtEOSubXact_Parallel.
     */
    dlist_delete(&pcxt->node);
 
    /* Kill each worker in turn, and forget their error queues. */
    if (pcxt->worker != NULL)
    {
        for (i = 0; i < pcxt->nworkers_launched; ++i)
        {
            if (pcxt->worker[i].error_mqh != NULL)
            {
                TerminateBackgroundWorker(pcxt->worker[i].bgwhandle);
 
                shm_mq_detach(pcxt->worker[i].error_mqh);
                pcxt->worker[i].error_mqh = NULL;
            }
        }
    }
 
    /*
     * If we have allocated a shared memory segment, detach it.  This will
     * implicitly detach the error queues, and any other shared memory queues,
     * stored there.
     */
    if (pcxt->seg != NULL)
    {
        dsm_detach(pcxt->seg);
        pcxt->seg = NULL;
    }
 
    /*
     * If this parallel context is actually in backend-private memory rather
     * than shared memory, free that memory instead.
     */
    if (pcxt->private_memory != NULL)
    {
        pfree(pcxt->private_memory);
        pcxt->private_memory = NULL;
    }
 
    /*
     * We can't finish transaction commit or abort until all of the workers
     * have exited.  This means, in particular, that we can't respond to
     * interrupts at this stage.
     */
    HOLD_INTERRUPTS();
    WaitForParallelWorkersToExit(pcxt);
    RESUME_INTERRUPTS();
 
    /* Free the worker array itself. */
    if (pcxt->worker != NULL)
    {
        pfree(pcxt->worker);
        pcxt->worker = NULL;
    }
 
    /* Free memory. */
    pfree(pcxt->library_name);
    pfree(pcxt->function_name);
    pfree(pcxt);
}

References ParallelWorkerInfo::bgwhandle, dlist_delete(), dsm_detach(), ParallelWorkerInfo::error_mqh, ParallelContext::function_name, HOLD_INTERRUPTS, i, ParallelContext::library_name, ParallelContext::node, ParallelContext::nworkers_launched, pfree(), ParallelContext::private_memory, RESUME_INTERRUPTS, ParallelContext::seg, shm_mq_detach(), TerminateBackgroundWorker(), WaitForParallelWorkersToExit(), and ParallelContext::worker.

Referenced by _brin_begin_parallel(), _brin_end_parallel(), _bt_begin_parallel(), _bt_end_parallel(), _gin_begin_parallel(), _gin_end_parallel(), AtEOSubXact_Parallel(), AtEOXact_Parallel(), ExecParallelCleanup(), and parallel_vacuum_end().

HandleParallelMessageInterrupt()

void HandleParallelMessageInterrupt

(

void

)

Definition at line 1044 of file parallel.c.

{
    InterruptPending = true;
    ParallelMessagePending = true;
    SetLatch(MyLatch);
}

References InterruptPending, MyLatch, ParallelMessagePending, and SetLatch().

Referenced by procsignal_sigusr1_handler().

InitializeParallelDSM()

void InitializeParallelDSM

(

ParallelContext *

pcxt

)

Definition at line 211 of file parallel.c.

{
    MemoryContext oldcontext;
    Size        library_len = 0;
    Size        guc_len = 0;
    Size        combocidlen = 0;
    Size        tsnaplen = 0;
    Size        asnaplen = 0;
    Size        tstatelen = 0;
    Size        pendingsyncslen = 0;
    Size        reindexlen = 0;
    Size        relmapperlen = 0;
    Size        uncommittedenumslen = 0;
    Size        clientconninfolen = 0;
    Size        segsize = 0;
    int         i;
    FixedParallelState *fps;
    dsm_handle  session_dsm_handle = DSM_HANDLE_INVALID;
    Snapshot    transaction_snapshot = GetTransactionSnapshot();
    Snapshot    active_snapshot = GetActiveSnapshot();
 
    /* We might be running in a very short-lived memory context. */
    oldcontext = MemoryContextSwitchTo(TopTransactionContext);
 
    /* Allow space to store the fixed-size parallel state. */
    shm_toc_estimate_chunk(&pcxt->estimator, sizeof(FixedParallelState));
    shm_toc_estimate_keys(&pcxt->estimator, 1);
 
    /*
     * If we manage to reach here while non-interruptible, it's unsafe to
     * launch any workers: we would fail to process interrupts sent by them.
     * We can deal with that edge case by pretending no workers were
     * requested.
     */
    if (!INTERRUPTS_CAN_BE_PROCESSED())
        pcxt->nworkers = 0;
 
    /*
     * Normally, the user will have requested at least one worker process, but
     * if by chance they have not, we can skip a bunch of things here.
     */
    if (pcxt->nworkers > 0)
    {
        /* Get (or create) the per-session DSM segment's handle. */
        session_dsm_handle = GetSessionDsmHandle();
 
        /*
         * If we weren't able to create a per-session DSM segment, then we can
         * continue but we can't safely launch any workers because their
         * record typmods would be incompatible so they couldn't exchange
         * tuples.
         */
        if (session_dsm_handle == DSM_HANDLE_INVALID)
            pcxt->nworkers = 0;
    }
 
    if (pcxt->nworkers > 0)
    {
        StaticAssertDecl(BUFFERALIGN(PARALLEL_ERROR_QUEUE_SIZE) ==
                         PARALLEL_ERROR_QUEUE_SIZE,
                         "parallel error queue size not buffer-aligned");
 
        /* Estimate space for various kinds of state sharing. */
        library_len = EstimateLibraryStateSpace();
        shm_toc_estimate_chunk(&pcxt->estimator, library_len);
        guc_len = EstimateGUCStateSpace();
        shm_toc_estimate_chunk(&pcxt->estimator, guc_len);
        combocidlen = EstimateComboCIDStateSpace();
        shm_toc_estimate_chunk(&pcxt->estimator, combocidlen);
        if (IsolationUsesXactSnapshot())
        {
            tsnaplen = EstimateSnapshotSpace(transaction_snapshot);
            shm_toc_estimate_chunk(&pcxt->estimator, tsnaplen);
        }
        asnaplen = EstimateSnapshotSpace(active_snapshot);
        shm_toc_estimate_chunk(&pcxt->estimator, asnaplen);
        tstatelen = EstimateTransactionStateSpace();
        shm_toc_estimate_chunk(&pcxt->estimator, tstatelen);
        shm_toc_estimate_chunk(&pcxt->estimator, sizeof(dsm_handle));
        pendingsyncslen = EstimatePendingSyncsSpace();
        shm_toc_estimate_chunk(&pcxt->estimator, pendingsyncslen);
        reindexlen = EstimateReindexStateSpace();
        shm_toc_estimate_chunk(&pcxt->estimator, reindexlen);
        relmapperlen = EstimateRelationMapSpace();
        shm_toc_estimate_chunk(&pcxt->estimator, relmapperlen);
        uncommittedenumslen = EstimateUncommittedEnumsSpace();
        shm_toc_estimate_chunk(&pcxt->estimator, uncommittedenumslen);
        clientconninfolen = EstimateClientConnectionInfoSpace();
        shm_toc_estimate_chunk(&pcxt->estimator, clientconninfolen);
        /* If you add more chunks here, you probably need to add keys. */
        shm_toc_estimate_keys(&pcxt->estimator, 12);
 
        /* Estimate space need for error queues. */
        shm_toc_estimate_chunk(&pcxt->estimator,
                               mul_size(PARALLEL_ERROR_QUEUE_SIZE,
                                        pcxt->nworkers));
        shm_toc_estimate_keys(&pcxt->estimator, 1);
 
        /* Estimate how much we'll need for the entrypoint info. */
        shm_toc_estimate_chunk(&pcxt->estimator, strlen(pcxt->library_name) +
                               strlen(pcxt->function_name) + 2);
        shm_toc_estimate_keys(&pcxt->estimator, 1);
    }
 
    /*
     * Create DSM and initialize with new table of contents.  But if the user
     * didn't request any workers, then don't bother creating a dynamic shared
     * memory segment; instead, just use backend-private memory.
     *
     * Also, if we can't create a dynamic shared memory segment because the
     * maximum number of segments have already been created, then fall back to
     * backend-private memory, and plan not to use any workers.  We hope this
     * won't happen very often, but it's better to abandon the use of
     * parallelism than to fail outright.
     */
    segsize = shm_toc_estimate(&pcxt->estimator);
    if (pcxt->nworkers > 0)
        pcxt->seg = dsm_create(segsize, DSM_CREATE_NULL_IF_MAXSEGMENTS);
    if (pcxt->seg != NULL)
        pcxt->toc = shm_toc_create(PARALLEL_MAGIC,
                                   dsm_segment_address(pcxt->seg),
                                   segsize);
    else
    {
        pcxt->nworkers = 0;
        pcxt->private_memory = MemoryContextAlloc(TopMemoryContext, segsize);
        pcxt->toc = shm_toc_create(PARALLEL_MAGIC, pcxt->private_memory,
                                   segsize);
    }
 
    /* Initialize fixed-size state in shared memory. */
    fps = (FixedParallelState *)
        shm_toc_allocate(pcxt->toc, sizeof(FixedParallelState));
    fps->database_id = MyDatabaseId;
    fps->authenticated_user_id = GetAuthenticatedUserId();
    fps->session_user_id = GetSessionUserId();
    fps->outer_user_id = GetCurrentRoleId();
    GetUserIdAndSecContext(&fps->current_user_id, &fps->sec_context);
    fps->session_user_is_superuser = GetSessionUserIsSuperuser();
    fps->role_is_superuser = current_role_is_superuser;
    GetTempNamespaceState(&fps->temp_namespace_id,
                          &fps->temp_toast_namespace_id);
    fps->parallel_leader_pgproc = MyProc;
    fps->parallel_leader_pid = MyProcPid;
    fps->parallel_leader_proc_number = MyProcNumber;
    fps->xact_ts = GetCurrentTransactionStartTimestamp();
    fps->stmt_ts = GetCurrentStatementStartTimestamp();
    fps->serializable_xact_handle = ShareSerializableXact();
    SpinLockInit(&fps->mutex);
    fps->last_xlog_end = 0;
    shm_toc_insert(pcxt->toc, PARALLEL_KEY_FIXED, fps);
 
    /* We can skip the rest of this if we're not budgeting for any workers. */
    if (pcxt->nworkers > 0)
    {
        char       *libraryspace;
        char       *gucspace;
        char       *combocidspace;
        char       *tsnapspace;
        char       *asnapspace;
        char       *tstatespace;
        char       *pendingsyncsspace;
        char       *reindexspace;
        char       *relmapperspace;
        char       *error_queue_space;
        char       *session_dsm_handle_space;
        char       *entrypointstate;
        char       *uncommittedenumsspace;
        char       *clientconninfospace;
        Size        lnamelen;
 
        /* Serialize shared libraries we have loaded. */
        libraryspace = shm_toc_allocate(pcxt->toc, library_len);
        SerializeLibraryState(library_len, libraryspace);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_LIBRARY, libraryspace);
 
        /* Serialize GUC settings. */
        gucspace = shm_toc_allocate(pcxt->toc, guc_len);
        SerializeGUCState(guc_len, gucspace);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_GUC, gucspace);
 
        /* Serialize combo CID state. */
        combocidspace = shm_toc_allocate(pcxt->toc, combocidlen);
        SerializeComboCIDState(combocidlen, combocidspace);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_COMBO_CID, combocidspace);
 
        /*
         * Serialize the transaction snapshot if the transaction isolation
         * level uses a transaction snapshot.
         */
        if (IsolationUsesXactSnapshot())
        {
            tsnapspace = shm_toc_allocate(pcxt->toc, tsnaplen);
            SerializeSnapshot(transaction_snapshot, tsnapspace);
            shm_toc_insert(pcxt->toc, PARALLEL_KEY_TRANSACTION_SNAPSHOT,
                           tsnapspace);
        }
 
        /* Serialize the active snapshot. */
        asnapspace = shm_toc_allocate(pcxt->toc, asnaplen);
        SerializeSnapshot(active_snapshot, asnapspace);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_ACTIVE_SNAPSHOT, asnapspace);
 
        /* Provide the handle for per-session segment. */
        session_dsm_handle_space = shm_toc_allocate(pcxt->toc,
                                                    sizeof(dsm_handle));
        *(dsm_handle *) session_dsm_handle_space = session_dsm_handle;
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_SESSION_DSM,
                       session_dsm_handle_space);
 
        /* Serialize transaction state. */
        tstatespace = shm_toc_allocate(pcxt->toc, tstatelen);
        SerializeTransactionState(tstatelen, tstatespace);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_TRANSACTION_STATE, tstatespace);
 
        /* Serialize pending syncs. */
        pendingsyncsspace = shm_toc_allocate(pcxt->toc, pendingsyncslen);
        SerializePendingSyncs(pendingsyncslen, pendingsyncsspace);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_PENDING_SYNCS,
                       pendingsyncsspace);
 
        /* Serialize reindex state. */
        reindexspace = shm_toc_allocate(pcxt->toc, reindexlen);
        SerializeReindexState(reindexlen, reindexspace);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_REINDEX_STATE, reindexspace);
 
        /* Serialize relmapper state. */
        relmapperspace = shm_toc_allocate(pcxt->toc, relmapperlen);
        SerializeRelationMap(relmapperlen, relmapperspace);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_RELMAPPER_STATE,
                       relmapperspace);
 
        /* Serialize uncommitted enum state. */
        uncommittedenumsspace = shm_toc_allocate(pcxt->toc,
                                                 uncommittedenumslen);
        SerializeUncommittedEnums(uncommittedenumsspace, uncommittedenumslen);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_UNCOMMITTEDENUMS,
                       uncommittedenumsspace);
 
        /* Serialize our ClientConnectionInfo. */
        clientconninfospace = shm_toc_allocate(pcxt->toc, clientconninfolen);
        SerializeClientConnectionInfo(clientconninfolen, clientconninfospace);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_CLIENTCONNINFO,
                       clientconninfospace);
 
        /* Allocate space for worker information. */
        pcxt->worker = palloc0_array(ParallelWorkerInfo, pcxt->nworkers);
 
        /*
         * Establish error queues in dynamic shared memory.
         *
         * These queues should be used only for transmitting ErrorResponse,
         * NoticeResponse, and NotifyResponse protocol messages.  Tuple data
         * should be transmitted via separate (possibly larger?) queues.
         */
        error_queue_space =
            shm_toc_allocate(pcxt->toc,
                             mul_size(PARALLEL_ERROR_QUEUE_SIZE,
                                      pcxt->nworkers));
        for (i = 0; i < pcxt->nworkers; ++i)
        {
            char       *start;
            shm_mq     *mq;
 
            start = error_queue_space + i * PARALLEL_ERROR_QUEUE_SIZE;
            mq = shm_mq_create(start, PARALLEL_ERROR_QUEUE_SIZE);
            shm_mq_set_receiver(mq, MyProc);
            pcxt->worker[i].error_mqh = shm_mq_attach(mq, pcxt->seg, NULL);
        }
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_ERROR_QUEUE, error_queue_space);
 
        /*
         * Serialize entrypoint information.  It's unsafe to pass function
         * pointers across processes, as the function pointer may be different
         * in each process in EXEC_BACKEND builds, so we always pass library
         * and function name.  (We use library name "postgres" for functions
         * in the core backend.)
         */
        lnamelen = strlen(pcxt->library_name);
        entrypointstate = shm_toc_allocate(pcxt->toc, lnamelen +
                                           strlen(pcxt->function_name) + 2);
        strcpy(entrypointstate, pcxt->library_name);
        strcpy(entrypointstate + lnamelen + 1, pcxt->function_name);
        shm_toc_insert(pcxt->toc, PARALLEL_KEY_ENTRYPOINT, entrypointstate);
    }
 
    /* Update nworkers_to_launch, in case we changed nworkers above. */
    pcxt->nworkers_to_launch = pcxt->nworkers;
 
    /* Restore previous memory context. */
    MemoryContextSwitchTo(oldcontext);
}

References FixedParallelState::authenticated_user_id, BUFFERALIGN, current_role_is_superuser, FixedParallelState::current_user_id, FixedParallelState::database_id, dsm_create(), DSM_CREATE_NULL_IF_MAXSEGMENTS, DSM_HANDLE_INVALID, dsm_segment_address(), ParallelWorkerInfo::error_mqh, EstimateClientConnectionInfoSpace(), EstimateComboCIDStateSpace(), EstimateGUCStateSpace(), EstimateLibraryStateSpace(), EstimatePendingSyncsSpace(), EstimateReindexStateSpace(), EstimateRelationMapSpace(), EstimateSnapshotSpace(), EstimateTransactionStateSpace(), EstimateUncommittedEnumsSpace(), ParallelContext::estimator, ParallelContext::function_name, GetActiveSnapshot(), GetAuthenticatedUserId(), GetCurrentRoleId(), GetCurrentStatementStartTimestamp(), GetCurrentTransactionStartTimestamp(), GetSessionDsmHandle(), GetSessionUserId(), GetSessionUserIsSuperuser(), GetTempNamespaceState(), GetTransactionSnapshot(), GetUserIdAndSecContext(), i, INTERRUPTS_CAN_BE_PROCESSED, IsolationUsesXactSnapshot, FixedParallelState::last_xlog_end, ParallelContext::library_name, MemoryContextAlloc(), MemoryContextSwitchTo(), mul_size(), FixedParallelState::mutex, MyDatabaseId, MyProc, MyProcNumber, MyProcPid, ParallelContext::nworkers, ParallelContext::nworkers_to_launch, FixedParallelState::outer_user_id, palloc0_array, PARALLEL_ERROR_QUEUE_SIZE, PARALLEL_KEY_ACTIVE_SNAPSHOT, PARALLEL_KEY_CLIENTCONNINFO, PARALLEL_KEY_COMBO_CID, PARALLEL_KEY_ENTRYPOINT, PARALLEL_KEY_ERROR_QUEUE, PARALLEL_KEY_FIXED, PARALLEL_KEY_GUC, PARALLEL_KEY_LIBRARY, PARALLEL_KEY_PENDING_SYNCS, PARALLEL_KEY_REINDEX_STATE, PARALLEL_KEY_RELMAPPER_STATE, PARALLEL_KEY_SESSION_DSM, PARALLEL_KEY_TRANSACTION_SNAPSHOT, PARALLEL_KEY_TRANSACTION_STATE, PARALLEL_KEY_UNCOMMITTEDENUMS, FixedParallelState::parallel_leader_pgproc, FixedParallelState::parallel_leader_pid, FixedParallelState::parallel_leader_proc_number, PARALLEL_MAGIC, ParallelContext::private_memory, FixedParallelState::role_is_superuser, FixedParallelState::sec_context, ParallelContext::seg, FixedParallelState::serializable_xact_handle, SerializeClientConnectionInfo(), SerializeComboCIDState(), SerializeGUCState(), SerializeLibraryState(), SerializePendingSyncs(), SerializeReindexState(), SerializeRelationMap(), SerializeSnapshot(), SerializeTransactionState(), SerializeUncommittedEnums(), FixedParallelState::session_user_id, FixedParallelState::session_user_is_superuser, ShareSerializableXact(), shm_mq_attach(), shm_mq_create(), shm_mq_set_receiver(), shm_toc_allocate(), shm_toc_create(), shm_toc_estimate(), shm_toc_estimate_chunk, shm_toc_estimate_keys, shm_toc_insert(), SpinLockInit, start, StaticAssertDecl, FixedParallelState::stmt_ts, FixedParallelState::temp_namespace_id, FixedParallelState::temp_toast_namespace_id, ParallelContext::toc, TopMemoryContext, TopTransactionContext, ParallelContext::worker, and FixedParallelState::xact_ts.

Referenced by _brin_begin_parallel(), _bt_begin_parallel(), _gin_begin_parallel(), ExecInitParallelPlan(), and parallel_vacuum_init().

LaunchParallelWorkers()

void LaunchParallelWorkers

(

ParallelContext *

pcxt

)

Definition at line 581 of file parallel.c.

{
    MemoryContext oldcontext;
    BackgroundWorker worker;
    int         i;
    bool        any_registrations_failed = false;
 
    /* Skip this if we have no workers. */
    if (pcxt->nworkers == 0 || pcxt->nworkers_to_launch == 0)
        return;
 
    /* We need to be a lock group leader. */
    BecomeLockGroupLeader();
 
    /* If we do have workers, we'd better have a DSM segment. */
    Assert(pcxt->seg != NULL);
 
    /* We might be running in a short-lived memory context. */
    oldcontext = MemoryContextSwitchTo(TopTransactionContext);
 
    /* Configure a worker. */
    memset(&worker, 0, sizeof(worker));
    snprintf(worker.bgw_name, BGW_MAXLEN, "parallel worker for PID %d",
             MyProcPid);
    snprintf(worker.bgw_type, BGW_MAXLEN, "parallel worker");
    worker.bgw_flags =
        BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION
        | BGWORKER_CLASS_PARALLEL;
    worker.bgw_start_time = BgWorkerStart_ConsistentState;
    worker.bgw_restart_time = BGW_NEVER_RESTART;
    sprintf(worker.bgw_library_name, "postgres");
    sprintf(worker.bgw_function_name, "ParallelWorkerMain");
    worker.bgw_main_arg = UInt32GetDatum(dsm_segment_handle(pcxt->seg));
    worker.bgw_notify_pid = MyProcPid;
 
    /*
     * Start workers.
     *
     * The caller must be able to tolerate ending up with fewer workers than
     * expected, so there is no need to throw an error here if registration
     * fails.  It wouldn't help much anyway, because registering the worker in
     * no way guarantees that it will start up and initialize successfully.
     */
    for (i = 0; i < pcxt->nworkers_to_launch; ++i)
    {
        memcpy(worker.bgw_extra, &i, sizeof(int));
        if (!any_registrations_failed &&
            RegisterDynamicBackgroundWorker(&worker,
                                            &pcxt->worker[i].bgwhandle))
        {
            shm_mq_set_handle(pcxt->worker[i].error_mqh,
                              pcxt->worker[i].bgwhandle);
            pcxt->nworkers_launched++;
        }
        else
        {
            /*
             * If we weren't able to register the worker, then we've bumped up
             * against the max_worker_processes limit, and future
             * registrations will probably fail too, so arrange to skip them.
             * But we still have to execute this code for the remaining slots
             * to make sure that we forget about the error queues we budgeted
             * for those workers.  Otherwise, we'll wait for them to start,
             * but they never will.
             */
            any_registrations_failed = true;
            pcxt->worker[i].bgwhandle = NULL;
            shm_mq_detach(pcxt->worker[i].error_mqh);
            pcxt->worker[i].error_mqh = NULL;
        }
    }
 
    /*
     * Now that nworkers_launched has taken its final value, we can initialize
     * known_attached_workers.
     */
    if (pcxt->nworkers_launched > 0)
    {
        pcxt->known_attached_workers = palloc0_array(bool, pcxt->nworkers_launched);
        pcxt->nknown_attached_workers = 0;
    }
 
    /* Restore previous memory context. */
    MemoryContextSwitchTo(oldcontext);
}

References Assert(), BecomeLockGroupLeader(), BackgroundWorker::bgw_extra, BackgroundWorker::bgw_flags, BackgroundWorker::bgw_function_name, BackgroundWorker::bgw_library_name, BackgroundWorker::bgw_main_arg, BGW_MAXLEN, BackgroundWorker::bgw_name, BGW_NEVER_RESTART, BackgroundWorker::bgw_notify_pid, BackgroundWorker::bgw_restart_time, BackgroundWorker::bgw_start_time, BackgroundWorker::bgw_type, ParallelWorkerInfo::bgwhandle, BGWORKER_BACKEND_DATABASE_CONNECTION, BGWORKER_CLASS_PARALLEL, BGWORKER_SHMEM_ACCESS, BgWorkerStart_ConsistentState, dsm_segment_handle(), ParallelWorkerInfo::error_mqh, i, ParallelContext::known_attached_workers, MemoryContextSwitchTo(), MyProcPid, ParallelContext::nknown_attached_workers, ParallelContext::nworkers, ParallelContext::nworkers_launched, ParallelContext::nworkers_to_launch, palloc0_array, RegisterDynamicBackgroundWorker(), ParallelContext::seg, shm_mq_detach(), shm_mq_set_handle(), snprintf, sprintf, TopTransactionContext, UInt32GetDatum(), and ParallelContext::worker.

Referenced by _brin_begin_parallel(), _bt_begin_parallel(), _gin_begin_parallel(), ExecGather(), ExecGatherMerge(), and parallel_vacuum_process_all_indexes().

ParallelContextActive()

bool ParallelContextActive

(

void

)

Definition at line 1031 of file parallel.c.

{
    return !dlist_is_empty(&pcxt_list);
}

References dlist_is_empty(), and pcxt_list.

Referenced by AtPrepare_PredicateLocks(), ExitParallelMode(), and ReleasePredicateLocks().

ParallelWorkerMain()

void ParallelWorkerMain

(

Datum

main_arg

)

Definition at line 1299 of file parallel.c.

{
    dsm_segment *seg;
    shm_toc    *toc;
    FixedParallelState *fps;
    char       *error_queue_space;
    shm_mq     *mq;
    shm_mq_handle *mqh;
    char       *libraryspace;
    char       *entrypointstate;
    char       *library_name;
    char       *function_name;
    parallel_worker_main_type entrypt;
    char       *gucspace;
    char       *combocidspace;
    char       *tsnapspace;
    char       *asnapspace;
    char       *tstatespace;
    char       *pendingsyncsspace;
    char       *reindexspace;
    char       *relmapperspace;
    char       *uncommittedenumsspace;
    char       *clientconninfospace;
    char       *session_dsm_handle_space;
    Snapshot    tsnapshot;
    Snapshot    asnapshot;
 
    /* Set flag to indicate that we're initializing a parallel worker. */
    InitializingParallelWorker = true;
 
    /* Establish signal handlers. */
    pqsignal(SIGTERM, die);
    BackgroundWorkerUnblockSignals();
 
    /* Determine and set our parallel worker number. */
    Assert(ParallelWorkerNumber == -1);
    memcpy(&ParallelWorkerNumber, MyBgworkerEntry->bgw_extra, sizeof(int));
 
    /* Set up a memory context to work in, just for cleanliness. */
    CurrentMemoryContext = AllocSetContextCreate(TopMemoryContext,
                                                 "Parallel worker",
                                                 ALLOCSET_DEFAULT_SIZES);
 
    /*
     * Attach to the dynamic shared memory segment for the parallel query, and
     * find its table of contents.
     *
     * Note: at this point, we have not created any ResourceOwner in this
     * process.  This will result in our DSM mapping surviving until process
     * exit, which is fine.  If there were a ResourceOwner, it would acquire
     * ownership of the mapping, but we have no need for that.
     */
    seg = dsm_attach(DatumGetUInt32(main_arg));
    if (seg == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("could not map dynamic shared memory segment")));
    toc = shm_toc_attach(PARALLEL_MAGIC, dsm_segment_address(seg));
    if (toc == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("invalid magic number in dynamic shared memory segment")));
 
    /* Look up fixed parallel state. */
    fps = shm_toc_lookup(toc, PARALLEL_KEY_FIXED, false);
    MyFixedParallelState = fps;
 
    /* Arrange to signal the leader if we exit. */
    ParallelLeaderPid = fps->parallel_leader_pid;
    ParallelLeaderProcNumber = fps->parallel_leader_proc_number;
    before_shmem_exit(ParallelWorkerShutdown, PointerGetDatum(seg));
 
    /*
     * Now we can find and attach to the error queue provided for us.  That's
     * good, because until we do that, any errors that happen here will not be
     * reported back to the process that requested that this worker be
     * launched.
     */
    error_queue_space = shm_toc_lookup(toc, PARALLEL_KEY_ERROR_QUEUE, false);
    mq = (shm_mq *) (error_queue_space +
                     ParallelWorkerNumber * PARALLEL_ERROR_QUEUE_SIZE);
    shm_mq_set_sender(mq, MyProc);
    mqh = shm_mq_attach(mq, seg, NULL);
    pq_redirect_to_shm_mq(seg, mqh);
    pq_set_parallel_leader(fps->parallel_leader_pid,
                           fps->parallel_leader_proc_number);
 
    /*
     * Hooray! Primary initialization is complete.  Now, we need to set up our
     * backend-local state to match the original backend.
     */
 
    /*
     * Join locking group.  We must do this before anything that could try to
     * acquire a heavyweight lock, because any heavyweight locks acquired to
     * this point could block either directly against the parallel group
     * leader or against some process which in turn waits for a lock that
     * conflicts with the parallel group leader, causing an undetected
     * deadlock.  (If we can't join the lock group, the leader has gone away,
     * so just exit quietly.)
     */
    if (!BecomeLockGroupMember(fps->parallel_leader_pgproc,
                               fps->parallel_leader_pid))
        return;
 
    /*
     * Restore transaction and statement start-time timestamps.  This must
     * happen before anything that would start a transaction, else asserts in
     * xact.c will fire.
     */
    SetParallelStartTimestamps(fps->xact_ts, fps->stmt_ts);
 
    /*
     * Identify the entry point to be called.  In theory this could result in
     * loading an additional library, though most likely the entry point is in
     * the core backend or in a library we just loaded.
     */
    entrypointstate = shm_toc_lookup(toc, PARALLEL_KEY_ENTRYPOINT, false);
    library_name = entrypointstate;
    function_name = entrypointstate + strlen(library_name) + 1;
 
    entrypt = LookupParallelWorkerFunction(library_name, function_name);
 
    /*
     * Restore current session authorization and role id.  No verification
     * happens here, we just blindly adopt the leader's state.  Note that this
     * has to happen before InitPostgres, since InitializeSessionUserId will
     * not set these variables.
     */
    SetAuthenticatedUserId(fps->authenticated_user_id);
    SetSessionAuthorization(fps->session_user_id,
                            fps->session_user_is_superuser);
    SetCurrentRoleId(fps->outer_user_id, fps->role_is_superuser);
 
    /*
     * Restore database connection.  We skip connection authorization checks,
     * reasoning that (a) the leader checked these things when it started, and
     * (b) we do not want parallel mode to cause these failures, because that
     * would make use of parallel query plans not transparent to applications.
     */
    BackgroundWorkerInitializeConnectionByOid(fps->database_id,
                                              fps->authenticated_user_id,
                                              BGWORKER_BYPASS_ALLOWCONN |
                                              BGWORKER_BYPASS_ROLELOGINCHECK);
 
    /*
     * Set the client encoding to the database encoding, since that is what
     * the leader will expect.  (We're cheating a bit by not calling
     * PrepareClientEncoding first.  It's okay because this call will always
     * result in installing a no-op conversion.  No error should be possible,
     * but check anyway.)
     */
    if (SetClientEncoding(GetDatabaseEncoding()) < 0)
        elog(ERROR, "SetClientEncoding(%d) failed", GetDatabaseEncoding());
 
    /*
     * Load libraries that were loaded by original backend.  We want to do
     * this before restoring GUCs, because the libraries might define custom
     * variables.
     */
    libraryspace = shm_toc_lookup(toc, PARALLEL_KEY_LIBRARY, false);
    StartTransactionCommand();
    RestoreLibraryState(libraryspace);
    CommitTransactionCommand();
 
    /* Crank up a transaction state appropriate to a parallel worker. */
    tstatespace = shm_toc_lookup(toc, PARALLEL_KEY_TRANSACTION_STATE, false);
    StartParallelWorkerTransaction(tstatespace);
 
    /*
     * Restore state that affects catalog access.  Ideally we'd do this even
     * before calling InitPostgres, but that has order-of-initialization
     * problems, and also the relmapper would get confused during the
     * CommitTransactionCommand call above.
     */
    pendingsyncsspace = shm_toc_lookup(toc, PARALLEL_KEY_PENDING_SYNCS,
                                       false);
    RestorePendingSyncs(pendingsyncsspace);
    relmapperspace = shm_toc_lookup(toc, PARALLEL_KEY_RELMAPPER_STATE, false);
    RestoreRelationMap(relmapperspace);
    reindexspace = shm_toc_lookup(toc, PARALLEL_KEY_REINDEX_STATE, false);
    RestoreReindexState(reindexspace);
    combocidspace = shm_toc_lookup(toc, PARALLEL_KEY_COMBO_CID, false);
    RestoreComboCIDState(combocidspace);
 
    /* Attach to the per-session DSM segment and contained objects. */
    session_dsm_handle_space =
        shm_toc_lookup(toc, PARALLEL_KEY_SESSION_DSM, false);
    AttachSession(*(dsm_handle *) session_dsm_handle_space);
 
    /*
     * If the transaction isolation level is REPEATABLE READ or SERIALIZABLE,
     * the leader has serialized the transaction snapshot and we must restore
     * it. At lower isolation levels, there is no transaction-lifetime
     * snapshot, but we need TransactionXmin to get set to a value which is
     * less than or equal to the xmin of every snapshot that will be used by
     * this worker. The easiest way to accomplish that is to install the
     * active snapshot as the transaction snapshot. Code running in this
     * parallel worker might take new snapshots via GetTransactionSnapshot()
     * or GetLatestSnapshot(), but it shouldn't have any way of acquiring a
     * snapshot older than the active snapshot.
     */
    asnapspace = shm_toc_lookup(toc, PARALLEL_KEY_ACTIVE_SNAPSHOT, false);
    tsnapspace = shm_toc_lookup(toc, PARALLEL_KEY_TRANSACTION_SNAPSHOT, true);
    asnapshot = RestoreSnapshot(asnapspace);
    tsnapshot = tsnapspace ? RestoreSnapshot(tsnapspace) : asnapshot;
    RestoreTransactionSnapshot(tsnapshot,
                               fps->parallel_leader_pgproc);
    PushActiveSnapshot(asnapshot);
 
    /*
     * We've changed which tuples we can see, and must therefore invalidate
     * system caches.
     */
    InvalidateSystemCaches();
 
    /*
     * Restore GUC values from launching backend.  We can't do this earlier,
     * because GUC check hooks that do catalog lookups need to see the same
     * database state as the leader.  Also, the check hooks for
     * session_authorization and role assume we already set the correct role
     * OIDs.
     */
    gucspace = shm_toc_lookup(toc, PARALLEL_KEY_GUC, false);
    RestoreGUCState(gucspace);
 
    /*
     * Restore current user ID and security context.  No verification happens
     * here, we just blindly adopt the leader's state.  We can't do this till
     * after restoring GUCs, else we'll get complaints about restoring
     * session_authorization and role.  (In effect, we're assuming that all
     * the restored values are okay to set, even if we are now inside a
     * restricted context.)
     */
    SetUserIdAndSecContext(fps->current_user_id, fps->sec_context);
 
    /* Restore temp-namespace state to ensure search path matches leader's. */
    SetTempNamespaceState(fps->temp_namespace_id,
                          fps->temp_toast_namespace_id);
 
    /* Restore uncommitted enums. */
    uncommittedenumsspace = shm_toc_lookup(toc, PARALLEL_KEY_UNCOMMITTEDENUMS,
                                           false);
    RestoreUncommittedEnums(uncommittedenumsspace);
 
    /* Restore the ClientConnectionInfo. */
    clientconninfospace = shm_toc_lookup(toc, PARALLEL_KEY_CLIENTCONNINFO,
                                         false);
    RestoreClientConnectionInfo(clientconninfospace);
 
    /*
     * Initialize SystemUser now that MyClientConnectionInfo is restored. Also
     * ensure that auth_method is actually valid, aka authn_id is not NULL.
     */
    if (MyClientConnectionInfo.authn_id)
        InitializeSystemUser(MyClientConnectionInfo.authn_id,
                             hba_authname(MyClientConnectionInfo.auth_method));
 
    /* Attach to the leader's serializable transaction, if SERIALIZABLE. */
    AttachSerializableXact(fps->serializable_xact_handle);
 
    /*
     * We've initialized all of our state now; nothing should change
     * hereafter.
     */
    InitializingParallelWorker = false;
    EnterParallelMode();
 
    /*
     * Time to do the real work: invoke the caller-supplied code.
     */
    entrypt(seg, toc);
 
    /* Must exit parallel mode to pop active snapshot. */
    ExitParallelMode();
 
    /* Must pop active snapshot so snapmgr.c doesn't complain. */
    PopActiveSnapshot();
 
    /* Shut down the parallel-worker transaction. */
    EndParallelWorkerTransaction();
 
    /* Detach from the per-session DSM segment. */
    DetachSession();
 
    /* Report success. */
    pq_putmessage(PqMsg_Terminate, NULL, 0);
}

References ALLOCSET_DEFAULT_SIZES, AllocSetContextCreate, Assert(), AttachSerializableXact(), AttachSession(), ClientConnectionInfo::auth_method, FixedParallelState::authenticated_user_id, ClientConnectionInfo::authn_id, BackgroundWorkerInitializeConnectionByOid(), BackgroundWorkerUnblockSignals(), BecomeLockGroupMember(), before_shmem_exit(), BackgroundWorker::bgw_extra, BGWORKER_BYPASS_ALLOWCONN, BGWORKER_BYPASS_ROLELOGINCHECK, CommitTransactionCommand(), FixedParallelState::current_user_id, CurrentMemoryContext, FixedParallelState::database_id, DatumGetUInt32(), DetachSession(), die, dsm_attach(), dsm_segment_address(), elog, EndParallelWorkerTransaction(), EnterParallelMode(), ereport, errcode(), errmsg(), ERROR, ExitParallelMode(), GetDatabaseEncoding(), hba_authname(), InitializeSystemUser(), InitializingParallelWorker, InvalidateSystemCaches(), LookupParallelWorkerFunction(), MyBgworkerEntry, MyClientConnectionInfo, MyFixedParallelState, MyProc, FixedParallelState::outer_user_id, PARALLEL_ERROR_QUEUE_SIZE, PARALLEL_KEY_ACTIVE_SNAPSHOT, PARALLEL_KEY_CLIENTCONNINFO, PARALLEL_KEY_COMBO_CID, PARALLEL_KEY_ENTRYPOINT, PARALLEL_KEY_ERROR_QUEUE, PARALLEL_KEY_FIXED, PARALLEL_KEY_GUC, PARALLEL_KEY_LIBRARY, PARALLEL_KEY_PENDING_SYNCS, PARALLEL_KEY_REINDEX_STATE, PARALLEL_KEY_RELMAPPER_STATE, PARALLEL_KEY_SESSION_DSM, PARALLEL_KEY_TRANSACTION_SNAPSHOT, PARALLEL_KEY_TRANSACTION_STATE, PARALLEL_KEY_UNCOMMITTEDENUMS, FixedParallelState::parallel_leader_pgproc, FixedParallelState::parallel_leader_pid, FixedParallelState::parallel_leader_proc_number, PARALLEL_MAGIC, ParallelLeaderPid, ParallelLeaderProcNumber, ParallelWorkerNumber, ParallelWorkerShutdown(), PointerGetDatum(), PopActiveSnapshot(), pq_putmessage, pq_redirect_to_shm_mq(), pq_set_parallel_leader(), PqMsg_Terminate, pqsignal, PushActiveSnapshot(), RestoreClientConnectionInfo(), RestoreComboCIDState(), RestoreGUCState(), RestoreLibraryState(), RestorePendingSyncs(), RestoreReindexState(), RestoreRelationMap(), RestoreSnapshot(), RestoreTransactionSnapshot(), RestoreUncommittedEnums(), FixedParallelState::role_is_superuser, FixedParallelState::sec_context, FixedParallelState::serializable_xact_handle, FixedParallelState::session_user_id, FixedParallelState::session_user_is_superuser, SetAuthenticatedUserId(), SetClientEncoding(), SetCurrentRoleId(), SetParallelStartTimestamps(), SetSessionAuthorization(), SetTempNamespaceState(), SetUserIdAndSecContext(), shm_mq_attach(), shm_mq_set_sender(), shm_toc_attach(), shm_toc_lookup(), StartParallelWorkerTransaction(), StartTransactionCommand(), FixedParallelState::stmt_ts, FixedParallelState::temp_namespace_id, FixedParallelState::temp_toast_namespace_id, TopMemoryContext, and FixedParallelState::xact_ts.

ParallelWorkerReportLastRecEnd()

void ParallelWorkerReportLastRecEnd

(

XLogRecPtr

last_xlog_end

)

Definition at line 1593 of file parallel.c.

{
    FixedParallelState *fps = MyFixedParallelState;
 
    Assert(fps != NULL);
    SpinLockAcquire(&fps->mutex);
    if (fps->last_xlog_end < last_xlog_end)
        fps->last_xlog_end = last_xlog_end;
    SpinLockRelease(&fps->mutex);
}

References Assert(), FixedParallelState::last_xlog_end, FixedParallelState::mutex, MyFixedParallelState, SpinLockAcquire, and SpinLockRelease.

Referenced by CommitTransaction().

ProcessParallelMessages()

void ProcessParallelMessages

(

void

)

Definition at line 1055 of file parallel.c.

{
    dlist_iter  iter;
    MemoryContext oldcontext;
 
    static MemoryContext hpm_context = NULL;
 
    /*
     * This is invoked from ProcessInterrupts(), and since some of the
     * functions it calls contain CHECK_FOR_INTERRUPTS(), there is a potential
     * for recursive calls if more signals are received while this runs.  It's
     * unclear that recursive entry would be safe, and it doesn't seem useful
     * even if it is safe, so let's block interrupts until done.
     */
    HOLD_INTERRUPTS();
 
    /*
     * Moreover, CurrentMemoryContext might be pointing almost anywhere.  We
     * don't want to risk leaking data into long-lived contexts, so let's do
     * our work here in a private context that we can reset on each use.
     */
    if (hpm_context == NULL)    /* first time through? */
        hpm_context = AllocSetContextCreate(TopMemoryContext,
                                            "ProcessParallelMessages",
                                            ALLOCSET_DEFAULT_SIZES);
    else
        MemoryContextReset(hpm_context);
 
    oldcontext = MemoryContextSwitchTo(hpm_context);
 
    /* OK to process messages.  Reset the flag saying there are more to do. */
    ParallelMessagePending = false;
 
    dlist_foreach(iter, &pcxt_list)
    {
        ParallelContext *pcxt;
        int         i;
 
        pcxt = dlist_container(ParallelContext, node, iter.cur);
        if (pcxt->worker == NULL)
            continue;
 
        for (i = 0; i < pcxt->nworkers_launched; ++i)
        {
            /*
             * Read as many messages as we can from each worker, but stop when
             * either (1) the worker's error queue goes away, which can happen
             * if we receive a Terminate message from the worker; or (2) no
             * more messages can be read from the worker without blocking.
             */
            while (pcxt->worker[i].error_mqh != NULL)
            {
                shm_mq_result res;
                Size        nbytes;
                void       *data;
 
                res = shm_mq_receive(pcxt->worker[i].error_mqh, &nbytes,
                                     &data, true);
                if (res == SHM_MQ_WOULD_BLOCK)
                    break;
                else if (res == SHM_MQ_SUCCESS)
                {
                    StringInfoData msg;
 
                    initStringInfo(&msg);
                    appendBinaryStringInfo(&msg, data, nbytes);
                    ProcessParallelMessage(pcxt, i, &msg);
                    pfree(msg.data);
                }
                else
                    ereport(ERROR,
                            (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                             errmsg("lost connection to parallel worker")));
            }
        }
    }
 
    MemoryContextSwitchTo(oldcontext);
 
    /* Might as well clear the context on our way out */
    MemoryContextReset(hpm_context);
 
    RESUME_INTERRUPTS();
}

References ALLOCSET_DEFAULT_SIZES, AllocSetContextCreate, appendBinaryStringInfo(), dlist_iter::cur, StringInfoData::data, data, dlist_container, dlist_foreach, ereport, errcode(), errmsg(), ERROR, ParallelWorkerInfo::error_mqh, HOLD_INTERRUPTS, i, initStringInfo(), MemoryContextReset(), MemoryContextSwitchTo(), ParallelContext::nworkers_launched, ParallelMessagePending, pcxt_list, pfree(), ProcessParallelMessage(), RESUME_INTERRUPTS, shm_mq_receive(), SHM_MQ_SUCCESS, SHM_MQ_WOULD_BLOCK, TopMemoryContext, and ParallelContext::worker.

Referenced by ProcessInterrupts().

ReinitializeParallelDSM()

void ReinitializeParallelDSM

(

ParallelContext *

pcxt

)

Definition at line 509 of file parallel.c.

{
    MemoryContext oldcontext;
    FixedParallelState *fps;
 
    /* We might be running in a very short-lived memory context. */
    oldcontext = MemoryContextSwitchTo(TopTransactionContext);
 
    /* Wait for any old workers to exit. */
    if (pcxt->nworkers_launched > 0)
    {
        WaitForParallelWorkersToFinish(pcxt);
        WaitForParallelWorkersToExit(pcxt);
        pcxt->nworkers_launched = 0;
        if (pcxt->known_attached_workers)
        {
            pfree(pcxt->known_attached_workers);
            pcxt->known_attached_workers = NULL;
            pcxt->nknown_attached_workers = 0;
        }
    }
 
    /* Reset a few bits of fixed parallel state to a clean state. */
    fps = shm_toc_lookup(pcxt->toc, PARALLEL_KEY_FIXED, false);
    fps->last_xlog_end = 0;
 
    /* Recreate error queues (if they exist). */
    if (pcxt->nworkers > 0)
    {
        char       *error_queue_space;
        int         i;
 
        error_queue_space =
            shm_toc_lookup(pcxt->toc, PARALLEL_KEY_ERROR_QUEUE, false);
        for (i = 0; i < pcxt->nworkers; ++i)
        {
            char       *start;
            shm_mq     *mq;
 
            start = error_queue_space + i * PARALLEL_ERROR_QUEUE_SIZE;
            mq = shm_mq_create(start, PARALLEL_ERROR_QUEUE_SIZE);
            shm_mq_set_receiver(mq, MyProc);
            pcxt->worker[i].error_mqh = shm_mq_attach(mq, pcxt->seg, NULL);
        }
    }
 
    /* Restore previous memory context. */
    MemoryContextSwitchTo(oldcontext);
}

References ParallelWorkerInfo::error_mqh, i, ParallelContext::known_attached_workers, FixedParallelState::last_xlog_end, MemoryContextSwitchTo(), MyProc, ParallelContext::nknown_attached_workers, ParallelContext::nworkers, ParallelContext::nworkers_launched, PARALLEL_ERROR_QUEUE_SIZE, PARALLEL_KEY_ERROR_QUEUE, PARALLEL_KEY_FIXED, pfree(), ParallelContext::seg, shm_mq_attach(), shm_mq_create(), shm_mq_set_receiver(), shm_toc_lookup(), start, ParallelContext::toc, TopTransactionContext, WaitForParallelWorkersToExit(), WaitForParallelWorkersToFinish(), and ParallelContext::worker.

Referenced by ExecParallelReinitialize(), and parallel_vacuum_process_all_indexes().

ReinitializeParallelWorkers()

void ReinitializeParallelWorkers	(	ParallelContext *	pcxt,
		int	nworkers_to_launch
	)

Definition at line 566 of file parallel.c.

{
    /*
     * The number of workers that need to be launched must be less than the
     * number of workers with which the parallel context is initialized.  But
     * the caller might not know that InitializeParallelDSM reduced nworkers,
     * so just silently trim the request.
     */
    pcxt->nworkers_to_launch = Min(pcxt->nworkers, nworkers_to_launch);
}

References Min, ParallelContext::nworkers, and ParallelContext::nworkers_to_launch.

Referenced by parallel_vacuum_process_all_indexes().

WaitForParallelWorkersToAttach()

void WaitForParallelWorkersToAttach

(

ParallelContext *

pcxt

)

Definition at line 700 of file parallel.c.

{
    int         i;
 
    /* Skip this if we have no launched workers. */
    if (pcxt->nworkers_launched == 0)
        return;
 
    for (;;)
    {
        /*
         * This will process any parallel messages that are pending and it may
         * also throw an error propagated from a worker.
         */
        CHECK_FOR_INTERRUPTS();
 
        for (i = 0; i < pcxt->nworkers_launched; ++i)
        {
            BgwHandleStatus status;
            shm_mq     *mq;
            int         rc;
            pid_t       pid;
 
            if (pcxt->known_attached_workers[i])
                continue;
 
            /*
             * If error_mqh is NULL, then the worker has already exited
             * cleanly.
             */
            if (pcxt->worker[i].error_mqh == NULL)
            {
                pcxt->known_attached_workers[i] = true;
                ++pcxt->nknown_attached_workers;
                continue;
            }
 
            status = GetBackgroundWorkerPid(pcxt->worker[i].bgwhandle, &pid);
            if (status == BGWH_STARTED)
            {
                /* Has the worker attached to the error queue? */
                mq = shm_mq_get_queue(pcxt->worker[i].error_mqh);
                if (shm_mq_get_sender(mq) != NULL)
                {
                    /* Yes, so it is known to be attached. */
                    pcxt->known_attached_workers[i] = true;
                    ++pcxt->nknown_attached_workers;
                }
            }
            else if (status == BGWH_STOPPED)
            {
                /*
                 * If the worker stopped without attaching to the error queue,
                 * throw an error.
                 */
                mq = shm_mq_get_queue(pcxt->worker[i].error_mqh);
                if (shm_mq_get_sender(mq) == NULL)
                    ereport(ERROR,
                            (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                             errmsg("parallel worker failed to initialize"),
                             errhint("More details may be available in the server log.")));
 
                pcxt->known_attached_workers[i] = true;
                ++pcxt->nknown_attached_workers;
            }
            else
            {
                /*
                 * Worker not yet started, so we must wait.  The postmaster
                 * will notify us if the worker's state changes.  Our latch
                 * might also get set for some other reason, but if so we'll
                 * just end up waiting for the same worker again.
                 */
                rc = WaitLatch(MyLatch,
                               WL_LATCH_SET | WL_EXIT_ON_PM_DEATH,
                               -1, WAIT_EVENT_BGWORKER_STARTUP);
 
                if (rc & WL_LATCH_SET)
                    ResetLatch(MyLatch);
            }
        }
 
        /* If all workers are known to have started, we're done. */
        if (pcxt->nknown_attached_workers >= pcxt->nworkers_launched)
        {
            Assert(pcxt->nknown_attached_workers == pcxt->nworkers_launched);
            break;
        }
    }
}

References Assert(), BGWH_STARTED, BGWH_STOPPED, ParallelWorkerInfo::bgwhandle, CHECK_FOR_INTERRUPTS, ereport, errcode(), errhint(), errmsg(), ERROR, ParallelWorkerInfo::error_mqh, GetBackgroundWorkerPid(), i, ParallelContext::known_attached_workers, MyLatch, ParallelContext::nknown_attached_workers, ParallelContext::nworkers_launched, ResetLatch(), shm_mq_get_queue(), shm_mq_get_sender(), WaitLatch(), WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, and ParallelContext::worker.

Referenced by _brin_begin_parallel(), _bt_begin_parallel(), and _gin_begin_parallel().

WaitForParallelWorkersToFinish()

void WaitForParallelWorkersToFinish

(

ParallelContext *

pcxt

)

Definition at line 803 of file parallel.c.

{
    for (;;)
    {
        bool        anyone_alive = false;
        int         nfinished = 0;
        int         i;
 
        /*
         * This will process any parallel messages that are pending, which may
         * change the outcome of the loop that follows.  It may also throw an
         * error propagated from a worker.
         */
        CHECK_FOR_INTERRUPTS();
 
        for (i = 0; i < pcxt->nworkers_launched; ++i)
        {
            /*
             * If error_mqh is NULL, then the worker has already exited
             * cleanly.  If we have received a message through error_mqh from
             * the worker, we know it started up cleanly, and therefore we're
             * certain to be notified when it exits.
             */
            if (pcxt->worker[i].error_mqh == NULL)
                ++nfinished;
            else if (pcxt->known_attached_workers[i])
            {
                anyone_alive = true;
                break;
            }
        }
 
        if (!anyone_alive)
        {
            /* If all workers are known to have finished, we're done. */
            if (nfinished >= pcxt->nworkers_launched)
            {
                Assert(nfinished == pcxt->nworkers_launched);
                break;
            }
 
            /*
             * We didn't detect any living workers, but not all workers are
             * known to have exited cleanly.  Either not all workers have
             * launched yet, or maybe some of them failed to start or
             * terminated abnormally.
             */
            for (i = 0; i < pcxt->nworkers_launched; ++i)
            {
                pid_t       pid;
                shm_mq     *mq;
 
                /*
                 * If the worker is BGWH_NOT_YET_STARTED or BGWH_STARTED, we
                 * should just keep waiting.  If it is BGWH_STOPPED, then
                 * further investigation is needed.
                 */
                if (pcxt->worker[i].error_mqh == NULL ||
                    pcxt->worker[i].bgwhandle == NULL ||
                    GetBackgroundWorkerPid(pcxt->worker[i].bgwhandle,
                                           &pid) != BGWH_STOPPED)
                    continue;
 
                /*
                 * Check whether the worker ended up stopped without ever
                 * attaching to the error queue.  If so, the postmaster was
                 * unable to fork the worker or it exited without initializing
                 * properly.  We must throw an error, since the caller may
                 * have been expecting the worker to do some work before
                 * exiting.
                 */
                mq = shm_mq_get_queue(pcxt->worker[i].error_mqh);
                if (shm_mq_get_sender(mq) == NULL)
                    ereport(ERROR,
                            (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                             errmsg("parallel worker failed to initialize"),
                             errhint("More details may be available in the server log.")));
 
                /*
                 * The worker is stopped, but is attached to the error queue.
                 * Unless there's a bug somewhere, this will only happen when
                 * the worker writes messages and terminates after the
                 * CHECK_FOR_INTERRUPTS() near the top of this function and
                 * before the call to GetBackgroundWorkerPid().  In that case,
                 * our latch should have been set as well and the right things
                 * will happen on the next pass through the loop.
                 */
            }
        }
 
        (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, -1,
                         WAIT_EVENT_PARALLEL_FINISH);
        ResetLatch(MyLatch);
    }
 
    if (pcxt->toc != NULL)
    {
        FixedParallelState *fps;
 
        fps = shm_toc_lookup(pcxt->toc, PARALLEL_KEY_FIXED, false);
        if (fps->last_xlog_end > XactLastRecEnd)
            XactLastRecEnd = fps->last_xlog_end;
    }
}

References Assert(), BGWH_STOPPED, ParallelWorkerInfo::bgwhandle, CHECK_FOR_INTERRUPTS, ereport, errcode(), errhint(), errmsg(), ERROR, ParallelWorkerInfo::error_mqh, GetBackgroundWorkerPid(), i, ParallelContext::known_attached_workers, FixedParallelState::last_xlog_end, MyLatch, ParallelContext::nworkers_launched, PARALLEL_KEY_FIXED, ResetLatch(), shm_mq_get_queue(), shm_mq_get_sender(), shm_toc_lookup(), ParallelContext::toc, WaitLatch(), WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, ParallelContext::worker, and XactLastRecEnd.

Referenced by _brin_end_parallel(), _bt_end_parallel(), _gin_end_parallel(), ExecParallelFinish(), parallel_vacuum_process_all_indexes(), and ReinitializeParallelDSM().

Variable Documentation

InitializingParallelWorker

PGDLLIMPORT bool InitializingParallelWorker

extern

Definition at line 121 of file parallel.c.

Referenced by check_client_encoding(), check_role(), check_session_authorization(), check_transaction_deferrable(), check_transaction_isolation(), check_transaction_read_only(), InitializeSessionUserId(), and ParallelWorkerMain().

ParallelMessagePending

PGDLLIMPORT volatile sig_atomic_t ParallelMessagePending

extern

Definition at line 118 of file parallel.c.

Referenced by HandleParallelMessageInterrupt(), ProcessInterrupts(), and ProcessParallelMessages().

ParallelWorkerNumber

PGDLLIMPORT int ParallelWorkerNumber

extern

Definition at line 115 of file parallel.c.

Referenced by _brin_parallel_build_main(), _bt_parallel_build_main(), _gin_parallel_build_main(), BuildTupleHashTable(), ExecEndAgg(), ExecEndBitmapHeapScan(), ExecEndBitmapIndexScan(), ExecEndIndexOnlyScan(), ExecEndIndexScan(), ExecEndMemoize(), ExecHashInitializeWorker(), ExecParallelGetReceiver(), ExecParallelHashEnsureBatchAccessors(), ExecParallelHashJoinSetUpBatches(), ExecParallelHashRepartitionRest(), ExecParallelReportInstrumentation(), ExecSort(), parallel_vacuum_main(), ParallelQueryMain(), and ParallelWorkerMain().