Move the tuple freezing point in CLUSTER to a point further back in the past,

to avoid losing useful Xid information in not-so-old tuples.  This makes
CLUSTER behave the same as VACUUM as far a tuple-freezing behavior goes
(though CLUSTER does not yet advance the table's relfrozenxid).

While at it, move the actual freezing operation in rewriteheap.c to a more
appropriate place, and document it thoroughly.  This part of the patch from
Tom Lane.

diff --git a/src/backend/access/heap/rewriteheap.c b/src/backend/access/heap/rewriteheap.c
index be389c647aa8460dc165e13efbef1ec39d55221a..fe8edeedae7e3527cb17eff79a2516ec1efa05cf 100644 (file)
--- a/src/backend/access/heap/rewriteheap.c
+++ b/src/backend/access/heap/rewriteheap.c
@@ -96,7 +96,7 @@
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/access/heap/rewriteheap.c,v 1.4 2007/05/16 16:36:56 alvherre Exp $
+ *   $PostgreSQL: pgsql/src/backend/access/heap/rewriteheap.c,v 1.5 2007/05/17 15:28:29 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -123,6 +123,8 @@ typedef struct RewriteStateData
    bool            rs_use_wal;         /* must we WAL-log inserts? */
    TransactionId   rs_oldest_xmin;     /* oldest xmin used by caller to
                                         * determine tuple visibility */
+   TransactionId   rs_freeze_xid;      /* Xid that will be used as freeze
+                                        * cutoff point */
    MemoryContext   rs_cxt;             /* for hash tables and entries and
                                         * tuples in them */
    HTAB           *rs_unresolved_tups; /* unmatched A tuples */
@@ -171,6 +173,7 @@ static void raw_heap_insert(RewriteState state, HeapTuple tup);
  *
  * new_heap        new, locked heap relation to insert tuples to
  * oldest_xmin xid used by the caller to determine which tuples are dead
+ * freeze_xid  xid before which tuples will be frozen
  * use_wal     should the inserts to the new heap be WAL-logged?
  *
  * Returns an opaque RewriteState, allocated in current memory context,
@@ -178,7 +181,7 @@ static void raw_heap_insert(RewriteState state, HeapTuple tup);
  */
 RewriteState
 begin_heap_rewrite(Relation new_heap, TransactionId oldest_xmin,
-                  bool use_wal)
+                  TransactionId freeze_xid, bool use_wal)
 {
    RewriteState state;
    MemoryContext rw_cxt;
@@ -206,6 +209,7 @@ begin_heap_rewrite(Relation new_heap, TransactionId oldest_xmin,
    state->rs_buffer_valid = false;
    state->rs_use_wal = use_wal;
    state->rs_oldest_xmin = oldest_xmin;
+   state->rs_freeze_xid = freeze_xid;
    state->rs_cxt = rw_cxt;
 
    /* Initialize hash tables used to track update chains */
@@ -292,7 +296,9 @@ end_heap_rewrite(RewriteState state)
 /*
  * Add a tuple to the new heap.
  *
- * Visibility information is copied from the original tuple.
+ * Visibility information is copied from the original tuple, except that
+ * we "freeze" very-old tuples.  Note that since we scribble on new_tuple,
+ * it had better be temp storage not a pointer to the original tuple.
  *
  * state       opaque state as returned by begin_heap_rewrite
  * old_tuple   original tuple in the old heap
@@ -323,6 +329,17 @@ rewrite_heap_tuple(RewriteState state,
    new_tuple->t_data->t_infomask |=
        old_tuple->t_data->t_infomask & HEAP_XACT_MASK;
 
+   /*
+    * While we have our hands on the tuple, we may as well freeze any
+    * very-old xmin or xmax, so that future VACUUM effort can be saved.
+    *
+    * Note we abuse heap_freeze_tuple() a bit here, since it's expecting
+    * to be given a pointer to a tuple in a disk buffer.  It happens
+    * though that we can get the right things to happen by passing
+    * InvalidBuffer for the buffer.
+    */
+   heap_freeze_tuple(new_tuple->t_data, state->rs_freeze_xid, InvalidBuffer);
+
    /*
     * Invalid ctid means that ctid should point to the tuple itself.
     * We'll override it later if the tuple is part of an update chain.
@@ -538,8 +555,6 @@ raw_heap_insert(RewriteState state, HeapTuple tup)
    OffsetNumber    newoff;
    HeapTuple       heaptup;
 
-   heap_freeze_tuple(tup->t_data, state->rs_oldest_xmin, InvalidBuffer);
-
    /*
     * If the new tuple is too big for storage or contains already toasted
     * out-of-line attributes from some other relation, invoke the toaster.

diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index 656d7d710f04df45c65b7be416dd197eb7d04677..3eee46fbd0a27de62644efd3b13a519b24613f21 100644 (file)
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.159 2007/04/08 01:26:28 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.160 2007/05/17 15:28:29 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -29,6 +29,7 @@
 #include "catalog/namespace.h"
 #include "catalog/toasting.h"
 #include "commands/cluster.h"
+#include "commands/vacuum.h"
 #include "miscadmin.h"
 #include "storage/procarray.h"
 #include "utils/acl.h"
@@ -657,6 +658,7 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
    HeapTuple   tuple;
    bool        use_wal;
    TransactionId OldestXmin;
+   TransactionId FreezeXid;
    RewriteState rwstate;
 
    /*
@@ -688,11 +690,16 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
    /* use_wal off requires rd_targblock be initially invalid */
    Assert(NewHeap->rd_targblock == InvalidBlockNumber);
 
-   /* Get the cutoff xmin we'll use to weed out dead tuples */
-   OldestXmin = GetOldestXmin(OldHeap->rd_rel->relisshared, true);
+   /*
+    * compute xids used to freeze and weed out dead tuples.  We use -1
+    * freeze_min_age to avoid having CLUSTER freeze tuples earlier than
+    * a plain VACUUM would.
+    */
+   vacuum_set_xid_limits(-1, OldHeap->rd_rel->relisshared,
+                         &OldestXmin, &FreezeXid);
 
    /* Initialize the rewrite operation */
-   rwstate = begin_heap_rewrite(NewHeap, OldestXmin, use_wal);
+   rwstate = begin_heap_rewrite(NewHeap, OldestXmin, FreezeXid, use_wal);
 
    /*
     * Scan through the OldHeap in OldIndex order and copy each tuple into the

diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index f275448756f506b6e5bcdd6c4ce43837908eb242..93885579cbb39a49e7e99937c4a24ad3ecfaa192 100644 (file)
--- 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 1.350 2007/04/16 18:29:50 alvherre Exp $
+ *   $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.351 2007/05/17 15:28:29 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -566,7 +566,7 @@ get_rel_oids(List *relids, const RangeVar *vacrel, const char *stmttype)
  * vacuum_set_xid_limits() -- compute oldest-Xmin and freeze cutoff points
  */
 void
-vacuum_set_xid_limits(VacuumStmt *vacstmt, bool sharedRel,
+vacuum_set_xid_limits(int freeze_min_age, bool sharedRel,
                      TransactionId *oldestXmin,
                      TransactionId *freezeLimit)
 {
@@ -588,12 +588,12 @@ vacuum_set_xid_limits(VacuumStmt *vacstmt, bool sharedRel,
    Assert(TransactionIdIsNormal(*oldestXmin));
 
    /*
-    * Determine the minimum freeze age to use: as specified in the vacstmt,
+    * Determine the minimum freeze age to use: as specified by the caller,
     * or vacuum_freeze_min_age, but in any case not more than half
     * autovacuum_freeze_max_age, so that autovacuums to prevent XID
     * wraparound won't occur too frequently.
     */
-   freezemin = vacstmt->freeze_min_age;
+   freezemin = freeze_min_age;
    if (freezemin < 0)
        freezemin = vacuum_freeze_min_age;
    freezemin = Min(freezemin, autovacuum_freeze_max_age / 2);
@@ -1154,7 +1154,7 @@ full_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
                i;
    VRelStats  *vacrelstats;
 
-   vacuum_set_xid_limits(vacstmt, onerel->rd_rel->relisshared,
+   vacuum_set_xid_limits(vacstmt->freeze_min_age, onerel->rd_rel->relisshared,
                          &OldestXmin, &FreezeLimit);
 
    /*

diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 2b6d8a07f76b93f5700abd924f64761539ce706f..2c9a80540c39e1783c628a550fb3f1c6682c70fe 100644 (file)
--- a/src/backend/commands/vacuumlazy.c
+++ b/src/backend/commands/vacuumlazy.c
@@ -36,7 +36,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.88 2007/04/30 03:23:48 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.89 2007/05/17 15:28:29 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -158,7 +158,7 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
    else
        elevel = DEBUG2;
 
-   vacuum_set_xid_limits(vacstmt, onerel->rd_rel->relisshared,
+   vacuum_set_xid_limits(vacstmt->freeze_min_age, onerel->rd_rel->relisshared,
                          &OldestXmin, &FreezeLimit);
 
    vacrelstats = (LVRelStats *) palloc0(sizeof(LVRelStats));

diff --git a/src/include/access/rewriteheap.h b/src/include/access/rewriteheap.h
index e8f53246a81008ea3c828e5384a8ab4f815e82b7..4f9515d566f46b5c1677ddeb4579e3ccf3a89717 100644 (file)
--- a/src/include/access/rewriteheap.h
+++ b/src/include/access/rewriteheap.h
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/rewriteheap.h,v 1.1 2007/04/08 01:26:33 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/access/rewriteheap.h,v 1.2 2007/05/17 15:28:29 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -20,10 +20,11 @@
 typedef struct RewriteStateData *RewriteState;
 
 extern RewriteState begin_heap_rewrite(Relation NewHeap,
-                                      TransactionId OldestXmin, bool use_wal);
+                  TransactionId OldestXmin, TransactionId FreezeXid,
+                  bool use_wal);
 extern void end_heap_rewrite(RewriteState state);
 extern void rewrite_heap_tuple(RewriteState state, HeapTuple oldTuple,
-                              HeapTuple newTuple);
+                  HeapTuple newTuple);
 extern void rewrite_heap_dead_tuple(RewriteState state, HeapTuple oldTuple);
 
 #endif /* REWRITE_HEAP_H */

diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index b77fbf4c7197e77b7164450aa00dddcd951bef31..acb2f623e2729ac4f392c5390af45467b643410a 100644 (file)
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.70 2007/03/13 00:33:43 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.71 2007/05/17 15:28:29 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -119,7 +119,7 @@ extern void vac_update_relstats(Oid relid,
                    double num_tuples,
                    bool hasindex,
                    TransactionId frozenxid);
-extern void vacuum_set_xid_limits(VacuumStmt *vacstmt, bool sharedRel,
+extern void vacuum_set_xid_limits(int freeze_min_age, bool sharedRel,
                      TransactionId *oldestXmin,
                      TransactionId *freezeLimit);
 extern void vac_update_datfrozenxid(void);