Function SetTempTablespaces

src/backend/storage/file/fd.c:2972–2991

* SetTempTablespaces * * Define a list (actually an array) of OIDs of tablespaces to use for * temporary files. This list will be used until end of transaction, * unless this function is called again before then. It is caller's * responsibility that the passed-in array has adequate lifespan (typically * it'd be allocated in TopTransactionContext). * * Some entries of the array may be Inv

 * database's default tablespace should be used.
 */
void
SetTempTablespaces(Oid *tableSpaces, int numSpaces)
{
	Assert(numSpaces >= 0);
	tempTableSpaces = tableSpaces;
	numTempTableSpaces = numSpaces;

	/*
	 * Select a random starting point in the list.  This is to minimize
	 * conflicts between backends that are most likely sharing the same list
	 * of temp tablespaces.  Note that if we create multiple temp files in the
	 * same transaction, we'll advance circularly through the list --- this
	 * ensures that large temporary sort files are nicely spread across all
	 * available tablespaces.
	 */
	if (numSpaces > 1)
		nextTempTableSpace = random() % numSpaces;
	else
		nextTempTableSpace = 0;
}

/*
 * TempTablespacesAreSet