Allow rewriting ALTER TABLE to skip WAL logging.

Itagaki Takahiro, with small changes by me and Simon.

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 24cbe1dd9427f4f2e11154cc41aaa7e43fa3a244..3e0c8191c7ec43a15ca4f7b920882f6ff36c0563 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.304 2009/10/14 22:14:21 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.305 2009/11/04 12:24:23 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3037,6 +3037,9 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
        int                     i;
        ListCell   *l;
        EState     *estate;
+       CommandId       mycid;
+       BulkInsertState bistate;
+       int                     hi_options;
 
        /*
         * Open the relation(s).  We have surely already locked the existing
@@ -3051,6 +3054,29 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
        else
                newrel = NULL;
 
+       /*
+        * Prepare a BulkInsertState and options for heap_insert. Because
+        * we're building a new heap, we can skip WAL-logging and fsync it
+        * to disk at the end instead (unless WAL-logging is required for
+        * archiving). The FSM is empty too, so don't bother using it.
+        */
+       if (newrel)
+       {
+               mycid = GetCurrentCommandId(true);
+               bistate = GetBulkInsertState();
+
+               hi_options = HEAP_INSERT_SKIP_FSM;
+               if (!XLogArchivingActive())
+                       hi_options |= HEAP_INSERT_SKIP_WAL;
+       }
+       else
+       {
+               /* keep compiler quiet about using these uninitialized */
+               mycid = 0;
+               bistate = NULL;
+               hi_options = 0;
+       }
+
        /*
         * If we need to rewrite the table, the operation has to be propagated to
         * tables that use this table's rowtype as a column type.
@@ -3252,7 +3278,7 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
 
                        /* Write the tuple out to the new relation */
                        if (newrel)
-                               simple_heap_insert(newrel, tuple);
+                               heap_insert(newrel, tuple, mycid, hi_options, bistate);
 
                        ResetExprContext(econtext);
 
@@ -3270,7 +3296,15 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
 
        heap_close(oldrel, NoLock);
        if (newrel)
+       {
+               FreeBulkInsertState(bistate);
+
+               /* If we skipped writing WAL, then we need to sync the heap. */
+               if (hi_options & HEAP_INSERT_SKIP_WAL)
+                       heap_sync(newrel);
+
                heap_close(newrel, NoLock);
+       }
 }
 
 /*