Tom Lane wrote:
> Alvaro Herrera <[EMAIL PROTECTED]> writes:
> > The part about actually advancing relfrozenxid is still not done though ...
> 
> Right.  Are you intending to make that happen?

See attached patch.  I'm intending to apply this sometime tomorrow.

Note that affecting CLUSTER changes code used by the ALTER TABLE
rewriting stuff as well; so with this patch, the latter also advances
relfrozenxid.  I could have chosen to keep it as it was, but instead I
chose RecentXmin as the new freeze point.  This is correct, because when
the table is rewritten, all the tuples are marked the rewriting
transaction's Xid, so for all purposes it behaves like a new table.

Curiously enough, TOAST tables are handled as fallout of other code, so
we don't need to do anything additional for this to work.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
Index: src/backend/commands/cluster.c
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/backend/commands/cluster.c,v
retrieving revision 1.160
diff -c -p -r1.160 cluster.c
*** src/backend/commands/cluster.c	17 May 2007 15:28:29 -0000	1.160
--- src/backend/commands/cluster.c	18 May 2007 01:01:45 -0000
*************** typedef struct
*** 55,61 ****
  
  static void cluster_rel(RelToCluster *rv, bool recheck);
  static void rebuild_relation(Relation OldHeap, Oid indexOid);
! static void copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex);
  static List *get_tables_to_cluster(MemoryContext cluster_context);
  
  
--- 55,61 ----
  
  static void cluster_rel(RelToCluster *rv, bool recheck);
  static void rebuild_relation(Relation OldHeap, Oid indexOid);
! static TransactionId copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex);
  static List *get_tables_to_cluster(MemoryContext cluster_context);
  
  
*************** rebuild_relation(Relation OldHeap, Oid i
*** 513,518 ****
--- 513,519 ----
  	Oid			tableSpace = OldHeap->rd_rel->reltablespace;
  	Oid			OIDNewHeap;
  	char		NewHeapName[NAMEDATALEN];
+ 	TransactionId frozenXid;
  	ObjectAddress object;
  
  	/* Mark the correct index as clustered */
*************** rebuild_relation(Relation OldHeap, Oid i
*** 539,551 ****
  	/*
  	 * Copy the heap data into the new table in the desired order.
  	 */
! 	copy_heap_data(OIDNewHeap, tableOid, indexOid);
  
  	/* To make the new heap's data visible (probably not needed?). */
  	CommandCounterIncrement();
  
  	/* Swap the physical files of the old and new heaps. */
! 	swap_relation_files(tableOid, OIDNewHeap);
  
  	CommandCounterIncrement();
  
--- 540,552 ----
  	/*
  	 * Copy the heap data into the new table in the desired order.
  	 */
! 	frozenXid = copy_heap_data(OIDNewHeap, tableOid, indexOid);
  
  	/* To make the new heap's data visible (probably not needed?). */
  	CommandCounterIncrement();
  
  	/* Swap the physical files of the old and new heaps. */
! 	swap_relation_files(tableOid, OIDNewHeap, frozenXid);
  
  	CommandCounterIncrement();
  
*************** make_new_heap(Oid OIDOldHeap, const char
*** 641,649 ****
  }
  
  /*
!  * Do the physical copying of heap data.
   */
! static void
  copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
  {
  	Relation	NewHeap,
--- 642,651 ----
  }
  
  /*
!  * Do the physical copying of heap data.  Returns the TransactionId used as
!  * freeze cutoff point for the tuples.
   */
! static TransactionId
  copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
  {
  	Relation	NewHeap,
*************** copy_heap_data(Oid OIDNewHeap, Oid OIDOl
*** 816,821 ****
--- 818,825 ----
  	index_close(OldIndex, NoLock);
  	heap_close(OldHeap, NoLock);
  	heap_close(NewHeap, NoLock);
+ 
+ 	return FreezeXid;
  }
  
  /*
*************** copy_heap_data(Oid OIDNewHeap, Oid OIDOl
*** 826,834 ****
   *
   * Also swap any TOAST links, so that the toast data moves along with
   * the main-table data.
   */
  void
! swap_relation_files(Oid r1, Oid r2)
  {
  	Relation	relRelation;
  	HeapTuple	reltup1,
--- 830,845 ----
   *
   * Also swap any TOAST links, so that the toast data moves along with
   * the main-table data.
+  *
+  * Additionally, the first relation is marked with relfrozenxid set to
+  * frozenXid.  It seems a bit ugly to have this here, but all callers would
+  * have to do it anyway, so having it here saves a heap_update.  Note: the
+  * TOAST table needs no special handling, because since we swapped the links,
+  * the entry for the TOAST table will now contain RecentXmin in relfrozenxid,
+  * which is the correct value.
   */
  void
! swap_relation_files(Oid r1, Oid r2, TransactionId frozenXid)
  {
  	Relation	relRelation;
  	HeapTuple	reltup1,
*************** swap_relation_files(Oid r1, Oid r2)
*** 872,877 ****
--- 883,891 ----
  
  	/* we should not swap reltoastidxid */
  
+ 	/* set rel1's frozen Xid */
+ 	relform1->relfrozenxid = frozenXid;
+ 
  	/* swap size statistics too, since new rel has freshly-updated stats */
  	{
  		int4		swap_pages;
Index: src/backend/commands/tablecmds.c
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/backend/commands/tablecmds.c,v
retrieving revision 1.224
diff -c -p -r1.224 tablecmds.c
*** src/backend/commands/tablecmds.c	16 May 2007 17:28:20 -0000	1.224
--- src/backend/commands/tablecmds.c	18 May 2007 00:08:51 -0000
*************** ATRewriteTables(List **wqueue)
*** 2285,2292 ****
  			 */
  			ATRewriteTable(tab, OIDNewHeap);
  
! 			/* Swap the physical files of the old and new heaps. */
! 			swap_relation_files(tab->relid, OIDNewHeap);
  
  			CommandCounterIncrement();
  
--- 2285,2297 ----
  			 */
  			ATRewriteTable(tab, OIDNewHeap);
  
! 			/*
! 			 * Swap the physical files of the old and new heaps.  Since we are
! 			 * generating a new heap, we can use RecentXmin for the table's new
! 			 * relfrozenxid because we rewrote all the tuples on
! 			 * ATRewriteTable, so no older Xid remains on the table.
! 			 */
! 			swap_relation_files(tab->relid, OIDNewHeap, RecentXmin);
  
  			CommandCounterIncrement();
  
Index: src/include/commands/cluster.h
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/include/commands/cluster.h,v
retrieving revision 1.32
diff -c -p -r1.32 cluster.h
*** src/include/commands/cluster.h	13 Mar 2007 00:33:43 -0000	1.32
--- src/include/commands/cluster.h	18 May 2007 00:22:26 -0000
*************** extern void check_index_is_clusterable(R
*** 24,29 ****
  extern void mark_index_clustered(Relation rel, Oid indexOid);
  extern Oid make_new_heap(Oid OIDOldHeap, const char *NewName,
  			  Oid NewTableSpace);
! extern void swap_relation_files(Oid r1, Oid r2);
  
  #endif   /* CLUSTER_H */
--- 24,29 ----
  extern void mark_index_clustered(Relation rel, Oid indexOid);
  extern Oid make_new_heap(Oid OIDOldHeap, const char *NewName,
  			  Oid NewTableSpace);
! extern void swap_relation_files(Oid r1, Oid r2, TransactionId frozenXid);
  
  #endif   /* CLUSTER_H */
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