Function SharedFileSetInit

src/backend/storage/file/sharedfileset.c:63–121

* Initialize a space for temporary files that can be opened by other backends. * Other backends must attach to it before accessing it. Associate this * SharedFileSet with 'seg'. Any contained files will be deleted when the * last backend detaches. * * We can also use this interface if the temporary files are used only by * single backend but the files need to be opened and closed multiple

 * be deleted.
 */
void
SharedFileSetInit(SharedFileSet *fileset, dsm_segment *seg)
{
	static uint32 counter = 0;

	SpinLockInit(&fileset->mutex);
	fileset->refcnt = 1;
	fileset->creator_pid = MyProcPid;
	fileset->number = counter;
	counter = (counter + 1) % INT_MAX;

	/* Capture the tablespace OIDs so that all backends agree on them. */
	PrepareTempTablespaces();
	fileset->ntablespaces =
		GetTempTablespaces(&fileset->tablespaces[0],
						   lengthof(fileset->tablespaces));
	if (fileset->ntablespaces == 0)
	{
		/* If the GUC is empty, use current database's default tablespace */
		fileset->tablespaces[0] = MyDatabaseTableSpace;
		fileset->ntablespaces = 1;
	}
	else
	{
		int			i;

		/*
		 * An entry of InvalidOid means use the default tablespace for the
		 * current database.  Replace that now, to be sure that all users of
		 * the SharedFileSet agree on what to do.
		 */
		for (i = 0; i < fileset->ntablespaces; i++)
		{
			if (fileset->tablespaces[i] == InvalidOid)
				fileset->tablespaces[i] = MyDatabaseTableSpace;
		}
	}

	/* Register our cleanup callback. */
	if (seg)
		on_dsm_detach(seg, SharedFileSetOnDetach, PointerGetDatum(fileset));
	else
	{
		static bool registered_cleanup = false;

		if (!registered_cleanup)
		{
			/*
			 * We must not have registered any fileset before registering the
			 * fileset clean up.
			 */
			Assert(filesetlist == NIL);
			on_proc_exit(SharedFileSetDeleteOnProcExit, 0);
			registered_cleanup = true;
		}

		filesetlist = lcons((void *) fileset, filesetlist);
	}