*** pgsql/src/backend/access/nbtree/nbtree.c	2009/07/29 20:56:18	1.172
--- pgsql/src/backend/access/nbtree/nbtree.c	2009/12/19 01:32:33	1.173
***************
*** 12,18 ****
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * IDENTIFICATION
!  *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.171 2009/06/11 14:48:54 momjian Exp $
   *
   *-------------------------------------------------------------------------
   */
--- 12,18 ----
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * IDENTIFICATION
!  *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.172 2009/07/29 20:56:18 tgl Exp $
   *
   *-------------------------------------------------------------------------
   */
*************** typedef struct
*** 57,63 ****
  	IndexBulkDeleteCallback callback;
  	void	   *callback_state;
  	BTCycleId	cycleid;
! 	BlockNumber lastUsedPage;
  	BlockNumber totFreePages;	/* true total # of free pages */
  	MemoryContext pagedelcontext;
  } BTVacState;
--- 57,64 ----
  	IndexBulkDeleteCallback callback;
  	void	   *callback_state;
  	BTCycleId	cycleid;
! 	BlockNumber lastBlockVacuumed; 	/* last blkno reached by Vacuum scan */
! 	BlockNumber lastUsedPage;		/* blkno of last non-recyclable page */
  	BlockNumber totFreePages;	/* true total # of free pages */
  	MemoryContext pagedelcontext;
  } BTVacState;
*************** btvacuumscan(IndexVacuumInfo *info, Inde
*** 629,634 ****
--- 630,636 ----
  	vstate.callback = callback;
  	vstate.callback_state = callback_state;
  	vstate.cycleid = cycleid;
+ 	vstate.lastBlockVacuumed = BTREE_METAPAGE; /* Initialise at first block */
  	vstate.lastUsedPage = BTREE_METAPAGE;
  	vstate.totFreePages = 0;
  
*************** btvacuumscan(IndexVacuumInfo *info, Inde
*** 705,710 ****
--- 707,738 ----
  		num_pages = new_pages;
  	}
  
+ 	/*
+ 	 * InHotStandby we need to scan right up to the end of the index for
+ 	 * correct locking, so we may need to write a WAL record for the final
+ 	 * block in the index if it was not vacuumed. It's possible that VACUUMing
+ 	 * has actually removed zeroed pages at the end of the index so we need to
+ 	 * take care to issue the record for last actual block and not for the
+ 	 * last block that was scanned. Ignore empty indexes.
+ 	 */
+ 	if (XLogStandbyInfoActive() &&
+ 		num_pages > 1 && vstate.lastBlockVacuumed < (num_pages - 1))
+ 	{
+ 		Buffer		buf;
+ 
+ 		/*
+ 		 * We can't use _bt_getbuf() here because it always applies
+ 		 * _bt_checkpage(), which will barf on an all-zero page. We want to
+ 		 * recycle all-zero pages, not fail.  Also, we want to use a nondefault
+ 		 * buffer access strategy.
+ 		 */
+ 		buf = ReadBufferExtended(rel, MAIN_FORKNUM, num_pages - 1, RBM_NORMAL,
+ 								 info->strategy);
+ 		LockBufferForCleanup(buf);
+ 		_bt_delitems(rel, buf, NULL, 0, true, vstate.lastBlockVacuumed);
+ 		_bt_relbuf(rel, buf);
+ 	}
+ 
  	MemoryContextDelete(vstate.pagedelcontext);
  
  	/* update statistics */
*************** restart:
*** 847,852 ****
--- 875,900 ----
  				itup = (IndexTuple) PageGetItem(page,
  												PageGetItemId(page, offnum));
  				htup = &(itup->t_tid);
+ 
+ 				/*
+ 				 * During Hot Standby we currently assume that XLOG_BTREE_VACUUM
+ 				 * records do not produce conflicts. That is only true as long
+ 				 * as the callback function depends only upon whether the index
+ 				 * tuple refers to heap tuples removed in the initial heap scan.
+ 				 * When vacuum starts it derives a value of OldestXmin. Backends
+ 				 * taking later snapshots could have a RecentGlobalXmin with a
+ 				 * later xid than the vacuum's OldestXmin, so it is possible that
+ 				 * row versions deleted after OldestXmin could be marked as killed
+ 				 * by other backends. The callback function *could* look at the
+ 				 * index tuple state in isolation and decide to delete the index
+ 				 * tuple, though currently it does not. If it ever did, we would
+ 				 * need to reconsider whether XLOG_BTREE_VACUUM records should
+ 				 * cause conflicts. If they did cause conflicts they would be
+ 				 * fairly harsh conflicts, since we haven't yet worked out a way
+ 				 * to pass a useful value for latestRemovedXid on the
+ 				 * XLOG_BTREE_VACUUM records. This applies to *any* type of index
+ 				 * that marks index tuples as killed.
+ 				 */
  				if (callback(htup, callback_state))
  					deletable[ndeletable++] = offnum;
  			}
*************** restart:
*** 858,864 ****
  		 */
  		if (ndeletable > 0)
  		{
! 			_bt_delitems(rel, buf, deletable, ndeletable);
  			stats->tuples_removed += ndeletable;
  			/* must recompute maxoff */
  			maxoff = PageGetMaxOffsetNumber(page);
--- 906,924 ----
  		 */
  		if (ndeletable > 0)
  		{
! 			BlockNumber	lastBlockVacuumed = BufferGetBlockNumber(buf);
! 
! 			_bt_delitems(rel, buf, deletable, ndeletable, true, vstate->lastBlockVacuumed);
! 
! 			/*
! 			 * Keep track of the block number of the lastBlockVacuumed, so
! 			 * we can scan those blocks as well during WAL replay. This then
! 			 * provides concurrency protection and allows btrees to be used
! 			 * while in recovery.
! 			 */
! 			if (lastBlockVacuumed > vstate->lastBlockVacuumed)
! 				vstate->lastBlockVacuumed = lastBlockVacuumed;
! 
  			stats->tuples_removed += ndeletable;
  			/* must recompute maxoff */
  			maxoff = PageGetMaxOffsetNumber(page);