Index: src/backend/commands/vacuumlazy.c
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/backend/commands/vacuumlazy.c,v
retrieving revision 1.90
diff -c -p -r1.90 vacuumlazy.c
*** src/backend/commands/vacuumlazy.c	30 May 2007 20:11:57 -0000	1.90
--- src/backend/commands/vacuumlazy.c	30 Aug 2007 17:23:34 -0000
***************
*** 11,20 ****
   * on the number of tuples and pages we will keep track of at once.
   *
   * We are willing to use at most maintenance_work_mem memory space to keep
!  * track of dead tuples.  We initially allocate an array of TIDs of that size.
!  * If the array threatens to overflow, we suspend the heap scan phase and
!  * perform a pass of index cleanup and page compaction, then resume the heap
!  * scan with an empty TID array.
   *
   * We can limit the storage for page free space to MaxFSMPages entries,
   * since that's the most the free space map will be willing to remember
--- 11,22 ----
   * on the number of tuples and pages we will keep track of at once.
   *
   * We are willing to use at most maintenance_work_mem memory space to keep
!  * track of dead tuples.  We initially allocate an array of TIDs of that size,
!  * with an upper limit that depends on table size (this limit ensures we don't
!  * allocate a huge area uselessly for vacuuming small tables).  If the array
!  * threatens to overflow, we suspend the heap scan phase and perform a pass of
!  * index cleanup and page compaction, then resume the heap scan with an empty
!  * TID array.
   *
   * We can limit the storage for page free space to MaxFSMPages entries,
   * since that's the most the free space map will be willing to remember
***************
*** 68,73 ****
--- 70,81 ----
  #define REL_TRUNCATE_MINIMUM	1000
  #define REL_TRUNCATE_FRACTION	16
  
+ /*
+  * Guesstimation of number of dead tuples per page.  This is used to
+  * provide an upper limit to memory allocated when vacuuming small
+  * tables.
+  */
+ #define LAZY_ALLOC_TUPLES		200
  
  typedef struct LVRelStats
  {
*************** lazy_space_alloc(LVRelStats *vacrelstats
*** 971,979 ****
  
  	if (vacrelstats->hasindex)
  	{
! 		maxtuples = (maintenance_work_mem * 1024L) / sizeof(ItemPointerData);
  		maxtuples = Min(maxtuples, INT_MAX);
  		maxtuples = Min(maxtuples, MaxAllocSize / sizeof(ItemPointerData));
  		/* stay sane if small maintenance_work_mem */
  		maxtuples = Max(maxtuples, MaxHeapTuplesPerPage);
  	}
--- 979,990 ----
  
  	if (vacrelstats->hasindex)
  	{
! 		/* no need to allocate more space than we have pages */
! 		maxtuples = LAZY_ALLOC_TUPLES * relblocks;
! 		maxtuples = Min(maxtuples, (maintenance_work_mem * 1024L) / sizeof(ItemPointerData));
  		maxtuples = Min(maxtuples, INT_MAX);
  		maxtuples = Min(maxtuples, MaxAllocSize / sizeof(ItemPointerData));
+ 
  		/* stay sane if small maintenance_work_mem */
  		maxtuples = Max(maxtuples, MaxHeapTuplesPerPage);
  	}