Function ParallelWorkerMain

src/backend/access/transam/parallel.c:1299–1578

* Main entrypoint for parallel workers. */

 * Main entrypoint for parallel workers.
 */
void
ParallelWorkerMain(Datum main_arg)
{
	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;
	StringInfoData msgbuf;
	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")));