Actually there's a better way to do this, which is to count tuples

during the vacuumcleanup scan that we're going to do anyway.  Should
save a few cycles (one calculation per page, not per tuple) as well
as not having to depend on assumptions about heap and index being
in step.
I think this could probably be made to work for GIST too, but that
code looks messy enough that I'm disinclined to try right now.

diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index e28faef141d83b966f3ba34d7dad669e7ffbdb16..dd6f1df6d2e871ca410e55417bcb513d4499a1ba 100644 (file)
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.139 2006/02/11 23:31:33 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.140 2006/02/12 00:18:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -539,16 +539,12 @@ btbulkdelete(PG_FUNCTION_ARGS)
        IndexBulkDeleteCallback callback = (IndexBulkDeleteCallback) PG_GETARG_POINTER(1);
        void       *callback_state = (void *) PG_GETARG_POINTER(2);
        IndexBulkDeleteResult *result;
-       double          tuples_removed;
-       double          num_index_tuples;
+       double          tuples_removed = 0;
        OffsetNumber deletable[MaxOffsetNumber];
        int                     ndeletable;
        Buffer          buf;
        BlockNumber num_pages;
 
-       tuples_removed = 0;
-       num_index_tuples = 0;
-
        /*
         * The outer loop iterates over index leaf pages, the inner over items on
         * a leaf page.  We issue just one _bt_delitems() call per page, so as to
@@ -566,19 +562,12 @@ btbulkdelete(PG_FUNCTION_ARGS)
         * could be stopped on those.
         *
         * We can skip the scan entirely if there's nothing to delete (indicated
-        * by callback_state == NULL) and the index isn't partial.  For a partial
-        * index we must scan in order to derive a trustworthy tuple count.
+        * by callback_state == NULL).
         */
-       if (callback_state || vac_is_partial_index(rel))
-       {
+       if (callback_state)
                buf = _bt_get_endpoint(rel, 0, false);
-       }
        else
-       {
-               /* skip scan and set flag for btvacuumcleanup */
                buf = InvalidBuffer;
-               num_index_tuples = -1;
-       }
 
        if (BufferIsValid(buf))         /* check for empty index */
        {
@@ -634,8 +623,6 @@ btbulkdelete(PG_FUNCTION_ARGS)
                                                deletable[ndeletable++] = offnum;
                                                tuples_removed += 1;
                                        }
-                                       else
-                                               num_index_tuples += 1;
                                }
                        }
 
@@ -663,7 +650,7 @@ btbulkdelete(PG_FUNCTION_ARGS)
 
        result = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult));
        result->num_pages = num_pages;
-       result->num_index_tuples = num_index_tuples;
+       /* btvacuumcleanup will fill in num_index_tuples */
        result->tuples_removed = tuples_removed;
 
        PG_RETURN_POINTER(result);
@@ -687,6 +674,7 @@ btvacuumcleanup(PG_FUNCTION_ARGS)
        BlockNumber *freePages;
        int                     nFreePages,
                                maxFreePages;
+       double          num_index_tuples = 0;
        BlockNumber pages_deleted = 0;
        MemoryContext mycontext;
        MemoryContext oldcontext;
@@ -801,6 +789,12 @@ btvacuumcleanup(PG_FUNCTION_ARGS)
                        MemoryContextSwitchTo(oldcontext);
                        continue;                       /* pagedel released buffer */
                }
+               else if (P_ISLEAF(opaque))
+               {
+                       /* Count the index entries of live leaf pages */
+                       num_index_tuples += PageGetMaxOffsetNumber(page) + 1 -
+                               P_FIRSTDATAKEY(opaque);
+               }
                _bt_relbuf(rel, buf);
        }
 
@@ -847,16 +841,10 @@ btvacuumcleanup(PG_FUNCTION_ARGS)
 
        /* update statistics */
        stats->num_pages = num_pages;
+       stats->num_index_tuples = num_index_tuples;
        stats->pages_deleted = pages_deleted;
        stats->pages_free = nFreePages;
 
-       /* if btbulkdelete skipped the scan, use heap's tuple count */
-       if (stats->num_index_tuples < 0)
-       {
-               Assert(info->num_heap_tuples >= 0);
-               stats->num_index_tuples = info->num_heap_tuples;
-       }
-
        PG_RETURN_POINTER(stats);
 }