Function ExecHashJoinGetSavedTuple

src/backend/executor/nodeHashjoin.c:1619–1665

* ExecHashJoinGetSavedTuple * read the next tuple from a batch file. Return NULL if no more. * * On success, *hashvalue is set to the tuple's hash value, and the tuple * itself is stored in the given slot. */

 * itself is stored in the given slot.
 */
static TupleTableSlot *
ExecHashJoinGetSavedTuple(HashJoinState *hjstate,
						  BufFile *file,
						  uint32 *hashvalue,
						  TupleTableSlot *tupleSlot)
{
	uint32		header[2];
	size_t		nread;
	MinimalTuple tuple;

	/*
	 * We check for interrupts here because this is typically taken as an
	 * alternative code path to an ExecProcNode() call, which would include
	 * such a check.
	 */
	CHECK_FOR_INTERRUPTS();

	/*
	 * Since both the hash value and the MinimalTuple length word are uint32,
	 * we can read them both in one BufFileRead() call without any type
	 * cheating.
	 */
	nread = BufFileRead(file, (void *) header, sizeof(header));
	if (nread == 0)				/* end of file */
	{
		ExecClearTuple(tupleSlot);
		return NULL;
	}
	if (nread != sizeof(header))
		ereport(ERROR,
				(errcode_for_file_access(),
				 errmsg("could not read from hash-join temporary file: read only %zu of %zu bytes",
						nread, sizeof(header))));
	*hashvalue = header[0];
	tuple = (MinimalTuple) palloc(header[1]);
	tuple->t_len = header[1];
	nread = BufFileRead(file,
						(void *) ((char *) tuple + sizeof(uint32)),
						header[1] - sizeof(uint32));
	if (nread != header[1] - sizeof(uint32))
		ereport(ERROR,
				(errcode_for_file_access(),
				 errmsg("could not read from hash-join temporary file: read only %zu of %zu bytes",
						nread, header[1] - sizeof(uint32))));
	ExecForceStoreMinimalTuple(tuple, tupleSlot, true);
	return tupleSlot;
}


void