diff --git a/doc/src/sgml/spi.sgml b/doc/src/sgml/spi.sgml
index e39f99fbb3..9e37fc3a14 100644
--- a/doc/src/sgml/spi.sgml
+++ b/doc/src/sgml/spi.sgml
@@ -323,19 +323,23 @@ typedef struct SPITupleTable
     /* Public members */
     TupleDesc   tupdesc;        /* tuple descriptor */
     HeapTuple  *vals;           /* array of tuples */
+    uint64      numvals;        /* number of valid tuples */
 
     /* Private members, not intended for external callers */
+    uint64      alloced;        /* allocated length of vals array */
     MemoryContext tuptabcxt;    /* memory context of result table */
-    uint64      alloced;        /* # of alloced vals */
-    uint64      free;           /* # of free vals */
     slist_node  next;           /* link for internal bookkeeping */
     SubTransactionId subid;     /* subxact in which tuptable was created */
 } SPITupleTable;
 </programlisting>
-   <structfield>vals</structfield> and <structfield>tupdesc</structfield> can
-   be used by SPI callers, the remaining fields are internal.
-   <structfield>vals</structfield> is an array of pointers to rows.  (The number
-   of valid entries is given by <varname>SPI_processed</varname>.)
+   <structfield>tupdesc</structfield>,
+   <structfield>vals</structfield>, and
+   <structfield>numvals</structfield>
+   can be used by SPI callers; the remaining fields are internal.
+   <structfield>vals</structfield> is an array of pointers to rows.
+   The number of rows is given by <structfield>numvals</structfield>
+   (for somewhat historical reasons, this count is also returned
+   in <varname>SPI_processed</varname>).
    <structfield>tupdesc</structfield> is a row descriptor which you can pass to
    SPI functions dealing with rows.
   </para>
@@ -4631,12 +4635,12 @@ execq(PG_FUNCTION_ARGS)
      */
     if (ret &gt; 0 &amp;&amp; SPI_tuptable != NULL)
     {
-        TupleDesc tupdesc = SPI_tuptable-&gt;tupdesc;
         SPITupleTable *tuptable = SPI_tuptable;
+        TupleDesc tupdesc = tuptable-&gt;tupdesc;
         char buf[8192];
         uint64 j;
 
-        for (j = 0; j &lt; proc; j++)
+        for (j = 0; j &lt; tuptable-&gt;numvals; j++)
         {
             HeapTuple tuple = tuptable-&gt;vals[j];
             int i;
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 8eedb613a1..74f8d89bcb 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -1872,8 +1872,9 @@ spi_dest_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
 	slist_push_head(&_SPI_current->tuptables, &tuptable->next);
 
 	/* set up initial allocations */
-	tuptable->alloced = tuptable->free = 128;
+	tuptable->alloced = 128;
 	tuptable->vals = (HeapTuple *) palloc(tuptable->alloced * sizeof(HeapTuple));
+	tuptable->numvals = 0;
 	tuptable->tupdesc = CreateTupleDescCopy(typeinfo);
 
 	MemoryContextSwitchTo(oldcxt);
@@ -1899,18 +1900,18 @@ spi_printtup(TupleTableSlot *slot, DestReceiver *self)
 
 	oldcxt = MemoryContextSwitchTo(tuptable->tuptabcxt);
 
-	if (tuptable->free == 0)
+	if (tuptable->numvals >= tuptable->alloced)
 	{
 		/* Double the size of the pointer array */
-		tuptable->free = tuptable->alloced;
-		tuptable->alloced += tuptable->free;
+		uint64		newalloced = tuptable->alloced * 2;
+
 		tuptable->vals = (HeapTuple *) repalloc_huge(tuptable->vals,
-													 tuptable->alloced * sizeof(HeapTuple));
+													 newalloced * sizeof(HeapTuple));
+		tuptable->alloced = newalloced;
 	}
 
-	tuptable->vals[tuptable->alloced - tuptable->free] =
-		ExecCopySlotHeapTuple(slot);
-	(tuptable->free)--;
+	tuptable->vals[tuptable->numvals] = ExecCopySlotHeapTuple(slot);
+	(tuptable->numvals)++;
 
 	MemoryContextSwitchTo(oldcxt);
 
@@ -2324,8 +2325,7 @@ _SPI_execute_plan(SPIPlanPtr plan, ParamListInfo paramLI,
 
 				/* Update "processed" if stmt returned tuples */
 				if (_SPI_current->tuptable)
-					_SPI_current->processed = _SPI_current->tuptable->alloced -
-						_SPI_current->tuptable->free;
+					_SPI_current->processed = _SPI_current->tuptable->numvals;
 
 				res = SPI_OK_UTILITY;
 
@@ -2694,7 +2694,7 @@ _SPI_checktuples(void)
 
 	if (tuptable == NULL)		/* spi_dest_startup was not called */
 		failed = true;
-	else if (processed != (tuptable->alloced - tuptable->free))
+	else if (processed != tuptable->numvals)
 		failed = true;
 
 	return failed;
diff --git a/src/include/executor/spi.h b/src/include/executor/spi.h
index af4f8c875c..ad69a5ce43 100644
--- a/src/include/executor/spi.h
+++ b/src/include/executor/spi.h
@@ -24,11 +24,11 @@ typedef struct SPITupleTable
 	/* Public members */
 	TupleDesc	tupdesc;		/* tuple descriptor */
 	HeapTuple  *vals;			/* array of tuples */
+	uint64		numvals;		/* number of valid tuples */
 
 	/* Private members, not intended for external callers */
+	uint64		alloced;		/* allocated length of vals array */
 	MemoryContext tuptabcxt;	/* memory context of result table */
-	uint64		alloced;		/* # of alloced vals */
-	uint64		free;			/* # of free vals */
 	slist_node	next;			/* link for internal bookkeeping */
 	SubTransactionId subid;		/* subxact in which tuptable was created */
 } SPITupleTable;