Rename MaxTupleSize to MaxHeapTupleSize to clarify that it's not meant to

describe the maximum size of index tuples (which is typically AM-dependent
anyway); and consequently remove the bogus deduction for "special space"
that was built into it.

Adjust TOAST_TUPLE_THRESHOLD and TOAST_MAX_CHUNK_SIZE to avoid wasting two
bytes per toast chunk, and to ensure that the calculation correctly tracks any
future changes in page header size.  The computation had been inaccurate in a
way that didn't cause any harm except space wastage, but future changes could
have broken it more drastically.

Fix the calculation of BTMaxItemSize, which was formerly computed as 1 byte
more than it could safely be.  This didn't cause any harm in practice because
it's only compared against maxalign'd lengths, but future changes in the size
of page headers or btree special space could have exposed the problem.

initdb forced because of change in TOAST_MAX_CHUNK_SIZE, which alters the
storage of toast tables.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 43647d7989f..5f9f787eeea 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -13,7 +13,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.344 2007/02/01 19:10:26 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.345 2007/02/05 04:22:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1236,7 +1236,7 @@ scan_heap(VRelStats *vacrelstats, Relation onerel,
 				nunused;
 	double		free_space,
 				usable_free_space;
-	Size		min_tlen = MaxTupleSize;
+	Size		min_tlen = MaxHeapTupleSize;
 	Size		max_tlen = 0;
 	bool		do_shrinking = true;
 	VTupleLink	vtlinks = (VTupleLink) palloc(100 * sizeof(VTupleLinkData));