v26-0003-Separate-TBM-Shared-Private-Iterator-and-TBMIter.patch

From cadf9b662830ac19e71b40a9a8689feee83178a2 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Fri, 17 Jan 2025 17:20:28 -0500
Subject: [PATCH v26 3/5] Separate TBM[Shared|Private]Iterator and
 TBMIterateResult

Remove the TBMIterateResult member from the TBMPrivateIterator and
TBMSharedIterator and make tbm_[shared|private_]iterate() take a
TBMIterateResult as a parameter.

This will allow multiple TBMIterateResults to exist concurrently,
allowing asynchronous use of the TIDBitmap for prefetching.

tbm_[shared|private]_iterate() now sets blockno to InvalidBlockNumber
when the bitmap is exhausted instead of returning NULL.

BitmapHeapScan callers of tbm_iterate make a TBMIterateResult locally
and pass it in.

Because GIN only needs a single TBMIterateResult, we inline the
matchResult in the GinScanEntry to avoid having to separately manage
memory for the TBMIterateResult.
---
 src/backend/access/gin/ginget.c           | 51 +++++++++------
 src/backend/access/gin/ginscan.c          |  2 +-
 src/backend/access/heap/heapam_handler.c  | 30 ++++-----
 src/backend/executor/nodeBitmapHeapscan.c | 40 ++++++------
 src/backend/nodes/tidbitmap.c             | 79 +++++++++++------------
 src/include/access/gin_private.h          |  2 +-
 src/include/nodes/tidbitmap.h             |  6 +-
 7 files changed, 111 insertions(+), 99 deletions(-)

diff --git a/src/backend/access/gin/ginget.c b/src/backend/access/gin/ginget.c
index 330805626ee..7cf3dd2a4b9 100644
--- a/src/backend/access/gin/ginget.c
+++ b/src/backend/access/gin/ginget.c
@@ -332,10 +332,22 @@ restartScanEntry:
 	entry->list = NULL;
 	entry->nlist = 0;
 	entry->matchBitmap = NULL;
-	entry->matchResult = NULL;
 	entry->reduceResult = false;
 	entry->predictNumberResult = 0;
 
+	/*
+	 * MTODO: is it enough to set blockno to InvalidBlockNumber? In all the
+	 * places were we previously set matchResult to NULL, I just set blockno
+	 * to InvalidBlockNumber. It seems like this should be okay because that
+	 * is usually what we check before using the matchResult members. But it
+	 * might be safer to zero out the offsets array. But that is expensive.
+	 */
+	entry->matchResult.blockno = InvalidBlockNumber;
+	entry->matchResult.ntuples = 0;
+	entry->matchResult.recheck = true;
+	memset(entry->matchResult.offsets, 0,
+		   sizeof(OffsetNumber) * MaxHeapTuplesPerPage);
+
 	/*
 	 * we should find entry, and begin scan of posting tree or just store
 	 * posting list in memory
@@ -374,6 +386,7 @@ restartScanEntry:
 			{
 				if (entry->matchIterator)
 					tbm_end_private_iterate(entry->matchIterator);
+				entry->matchResult.blockno = InvalidBlockNumber;
 				entry->matchIterator = NULL;
 				tbm_free(entry->matchBitmap);
 				entry->matchBitmap = NULL;
@@ -824,19 +837,19 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
 		{
 			/*
 			 * If we've exhausted all items on this block, move to next block
-			 * in the bitmap.
+			 * in the bitmap. tbm_private_iterate() sets matchResult->blockno
+			 * to InvalidBlockNumber when the bitmap is exhausted.
 			 */
-			while (entry->matchResult == NULL ||
-				   (entry->matchResult->ntuples >= 0 &&
-					entry->offset >= entry->matchResult->ntuples) ||
-				   entry->matchResult->blockno < advancePastBlk ||
+			while ((!BlockNumberIsValid(entry->matchResult.blockno)) ||
+				   (entry->matchResult.ntuples >= 0 &&
+					entry->offset >= entry->matchResult.ntuples) ||
+				   entry->matchResult.blockno < advancePastBlk ||
 				   (ItemPointerIsLossyPage(&advancePast) &&
-					entry->matchResult->blockno == advancePastBlk))
+					entry->matchResult.blockno == advancePastBlk))
 			{
-				entry->matchResult =
-					tbm_private_iterate(entry->matchIterator);
+				tbm_private_iterate(entry->matchIterator, &entry->matchResult);
 
-				if (entry->matchResult == NULL)
+				if (!BlockNumberIsValid(entry->matchResult.blockno))
 				{
 					ItemPointerSetInvalid(&entry->curItem);
 					tbm_end_private_iterate(entry->matchIterator);
@@ -847,7 +860,7 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
 
 				/*
 				 * Reset counter to the beginning of entry->matchResult. Note:
-				 * entry->offset is still greater than matchResult->ntuples if
+				 * entry->offset is still greater than matchResult.ntuples if
 				 * matchResult is lossy.  So, on next call we will get next
 				 * result from TIDBitmap.
 				 */
@@ -860,10 +873,10 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
 			 * We're now on the first page after advancePast which has any
 			 * items on it. If it's a lossy result, return that.
 			 */
-			if (entry->matchResult->ntuples < 0)
+			if (entry->matchResult.ntuples < 0)
 			{
 				ItemPointerSetLossyPage(&entry->curItem,
-										entry->matchResult->blockno);
+										entry->matchResult.blockno);
 
 				/*
 				 * We might as well fall out of the loop; we could not
@@ -877,27 +890,27 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
 			 * Not a lossy page. Skip over any offsets <= advancePast, and
 			 * return that.
 			 */
-			if (entry->matchResult->blockno == advancePastBlk)
+			if (entry->matchResult.blockno == advancePastBlk)
 			{
 				/*
 				 * First, do a quick check against the last offset on the
 				 * page. If that's > advancePast, so are all the other
 				 * offsets, so just go back to the top to get the next page.
 				 */
-				if (entry->matchResult->offsets[entry->matchResult->ntuples - 1] <= advancePastOff)
+				if (entry->matchResult.offsets[entry->matchResult.ntuples - 1] <= advancePastOff)
 				{
-					entry->offset = entry->matchResult->ntuples;
+					entry->offset = entry->matchResult.ntuples;
 					continue;
 				}
 
 				/* Otherwise scan to find the first item > advancePast */
-				while (entry->matchResult->offsets[entry->offset] <= advancePastOff)
+				while (entry->matchResult.offsets[entry->offset] <= advancePastOff)
 					entry->offset++;
 			}
 
 			ItemPointerSet(&entry->curItem,
-						   entry->matchResult->blockno,
-						   entry->matchResult->offsets[entry->offset]);
+						   entry->matchResult.blockno,
+						   entry->matchResult.offsets[entry->offset]);
 			entry->offset++;
 
 			/* Done unless we need to reduce the result */
diff --git a/src/backend/access/gin/ginscan.c b/src/backend/access/gin/ginscan.c
index 7d1e6615260..625140fdf25 100644
--- a/src/backend/access/gin/ginscan.c
+++ b/src/backend/access/gin/ginscan.c
@@ -106,7 +106,7 @@ ginFillScanEntry(GinScanOpaque so, OffsetNumber attnum,
 	ItemPointerSetMin(&scanEntry->curItem);
 	scanEntry->matchBitmap = NULL;
 	scanEntry->matchIterator = NULL;
-	scanEntry->matchResult = NULL;
+	scanEntry->matchResult.blockno = InvalidBlockNumber;
 	scanEntry->list = NULL;
 	scanEntry->nlist = 0;
 	scanEntry->offset = InvalidOffsetNumber;
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index a4003cf59e1..bd567760f2d 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -2124,7 +2124,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
 	Buffer		buffer;
 	Snapshot	snapshot;
 	int			ntup;
-	TBMIterateResult *tbmres;
+	TBMIterateResult tbmres;
 
 	Assert(scan->rs_flags & SO_TYPE_BITMAPSCAN);
 
@@ -2138,9 +2138,9 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
 	{
 		CHECK_FOR_INTERRUPTS();
 
-		tbmres = tbm_iterate(&scan->st.rs_tbmiterator);
+		tbm_iterate(&scan->st.rs_tbmiterator, &tbmres);
 
-		if (tbmres == NULL)
+		if (!BlockNumberIsValid(tbmres.blockno))
 			return false;
 
 		/*
@@ -2152,11 +2152,11 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
 		 * reachable by the index.
 		 */
 	} while (!IsolationIsSerializable() &&
-			 tbmres->blockno >= hscan->rs_nblocks);
+			 tbmres.blockno >= hscan->rs_nblocks);
 
 	/* Got a valid block */
-	*blockno = tbmres->blockno;
-	*recheck = tbmres->recheck;
+	*blockno = tbmres.blockno;
+	*recheck = tbmres.recheck;
 
 	/*
 	 * We can skip fetching the heap page if we don't need any fields from the
@@ -2164,19 +2164,19 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
 	 * page are visible to our transaction.
 	 */
 	if (!(scan->rs_flags & SO_NEED_TUPLES) &&
-		!tbmres->recheck &&
-		VM_ALL_VISIBLE(scan->rs_rd, tbmres->blockno, &bscan->rs_vmbuffer))
+		!tbmres.recheck &&
+		VM_ALL_VISIBLE(scan->rs_rd, tbmres.blockno, &bscan->rs_vmbuffer))
 	{
 		/* can't be lossy in the skip_fetch case */
-		Assert(tbmres->ntuples >= 0);
+		Assert(tbmres.ntuples >= 0);
 		Assert(bscan->rs_empty_tuples_pending >= 0);
 
-		bscan->rs_empty_tuples_pending += tbmres->ntuples;
+		bscan->rs_empty_tuples_pending += tbmres.ntuples;
 
 		return true;
 	}
 
-	block = tbmres->blockno;
+	block = tbmres.blockno;
 
 	/*
 	 * Acquire pin on the target heap page, trading in any pin we held before.
@@ -2205,7 +2205,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
 	/*
 	 * We need two separate strategies for lossy and non-lossy cases.
 	 */
-	if (tbmres->ntuples >= 0)
+	if (tbmres.ntuples >= 0)
 	{
 		/*
 		 * Bitmap is non-lossy, so we just look through the offsets listed in
@@ -2214,9 +2214,9 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
 		 */
 		int			curslot;
 
-		for (curslot = 0; curslot < tbmres->ntuples; curslot++)
+		for (curslot = 0; curslot < tbmres.ntuples; curslot++)
 		{
-			OffsetNumber offnum = tbmres->offsets[curslot];
+			OffsetNumber offnum = tbmres.offsets[curslot];
 			ItemPointerData tid;
 			HeapTupleData heapTuple;
 
@@ -2266,7 +2266,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
 	Assert(ntup <= MaxHeapTuplesPerPage);
 	hscan->rs_ntuples = ntup;
 
-	if (tbmres->ntuples >= 0)
+	if (tbmres.ntuples >= 0)
 		(*exact_pages)++;
 	else
 		(*lossy_pages)++;
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index 92a199c1e87..da3c76f4744 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -316,7 +316,7 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node)
 {
 #ifdef USE_PREFETCH
 	ParallelBitmapHeapState *pstate = node->pstate;
-	TBMIterateResult *tbmpre;
+	TBMIterateResult tbmpre;
 
 	if (pstate == NULL)
 	{
@@ -329,9 +329,8 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node)
 		}
 		else if (!tbm_exhausted(prefetch_iterator))
 		{
-			tbmpre = tbm_iterate(prefetch_iterator);
-			node->prefetch_blockno = tbmpre ? tbmpre->blockno :
-				InvalidBlockNumber;
+			tbm_iterate(prefetch_iterator, &tbmpre);
+			node->prefetch_blockno = tbmpre.blockno;
 		}
 		return;
 	}
@@ -370,9 +369,8 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node)
 			 */
 			if (!tbm_exhausted(prefetch_iterator))
 			{
-				tbmpre = tbm_iterate(prefetch_iterator);
-				node->prefetch_blockno = tbmpre ? tbmpre->blockno :
-					InvalidBlockNumber;
+				tbm_iterate(prefetch_iterator, &tbmpre);
+				node->prefetch_blockno = tbmpre.blockno;
 			}
 		}
 	}
@@ -440,17 +438,19 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
 		{
 			while (node->prefetch_pages < node->prefetch_target)
 			{
-				TBMIterateResult *tbmpre = tbm_iterate(prefetch_iterator);
+				TBMIterateResult tbmpre;
 				bool		skip_fetch;
 
-				if (tbmpre == NULL)
+				tbm_iterate(prefetch_iterator, &tbmpre);
+
+				if (!BlockNumberIsValid(tbmpre.blockno))
 				{
 					/* No more pages to prefetch */
 					tbm_end_iterate(prefetch_iterator);
 					break;
 				}
 				node->prefetch_pages++;
-				node->prefetch_blockno = tbmpre->blockno;
+				node->prefetch_blockno = tbmpre.blockno;
 
 				/*
 				 * If we expect not to have to actually read this heap page,
@@ -459,13 +459,13 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
 				 * prefetch_pages?)
 				 */
 				skip_fetch = (!(scan->rs_flags & SO_NEED_TUPLES) &&
-							  !tbmpre->recheck &&
+							  !tbmpre.recheck &&
 							  VM_ALL_VISIBLE(node->ss.ss_currentRelation,
-											 tbmpre->blockno,
+											 tbmpre.blockno,
 											 &node->pvmbuffer));
 
 				if (!skip_fetch)
-					PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre->blockno);
+					PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre.blockno);
 			}
 		}
 
@@ -480,7 +480,7 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
 		{
 			while (1)
 			{
-				TBMIterateResult *tbmpre;
+				TBMIterateResult tbmpre;
 				bool		do_prefetch = false;
 				bool		skip_fetch;
 
@@ -499,25 +499,25 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
 				if (!do_prefetch)
 					return;
 
-				tbmpre = tbm_iterate(prefetch_iterator);
-				if (tbmpre == NULL)
+				tbm_iterate(prefetch_iterator, &tbmpre);
+				if (!BlockNumberIsValid(tbmpre.blockno))
 				{
 					/* No more pages to prefetch */
 					tbm_end_iterate(prefetch_iterator);
 					break;
 				}
 
-				node->prefetch_blockno = tbmpre->blockno;
+				node->prefetch_blockno = tbmpre.blockno;
 
 				/* As above, skip prefetch if we expect not to need page */
 				skip_fetch = (!(scan->rs_flags & SO_NEED_TUPLES) &&
-							  !tbmpre->recheck &&
+							  !tbmpre.recheck &&
 							  VM_ALL_VISIBLE(node->ss.ss_currentRelation,
-											 tbmpre->blockno,
+											 tbmpre.blockno,
 											 &node->pvmbuffer));
 
 				if (!skip_fetch)
-					PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre->blockno);
+					PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre.blockno);
 			}
 		}
 	}
diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
index 3d38cc04cc5..40d7b9f7505 100644
--- a/src/backend/nodes/tidbitmap.c
+++ b/src/backend/nodes/tidbitmap.c
@@ -172,7 +172,6 @@ struct TBMPrivateIterator
 	int			spageptr;		/* next spages index */
 	int			schunkptr;		/* next schunks index */
 	int			schunkbit;		/* next bit to check in current schunk */
-	TBMIterateResult output;
 };
 
 /*
@@ -213,7 +212,6 @@ struct TBMSharedIterator
 	PTEntryArray *ptbase;		/* pagetable element array */
 	PTIterationArray *ptpages;	/* sorted exact page index list */
 	PTIterationArray *ptchunks; /* sorted lossy page index list */
-	TBMIterateResult output;
 };
 
 /* Local function prototypes */
@@ -948,20 +946,21 @@ tbm_advance_schunkbit(PagetableEntry *chunk, int *schunkbitp)
 /*
  * tbm_private_iterate - scan through next page of a TIDBitmap
  *
- * Returns a TBMIterateResult representing one page, or NULL if there are
- * no more pages to scan.  Pages are guaranteed to be delivered in numerical
- * order.  If result->ntuples < 0, then the bitmap is "lossy" and failed to
- * remember the exact tuples to look at on this page --- the caller must
- * examine all tuples on the page and check if they meet the intended
- * condition.  If result->recheck is true, only the indicated tuples need
- * be examined, but the condition must be rechecked anyway.  (For ease of
- * testing, recheck is always set true when ntuples < 0.)
+ * Caller must pass in a TBMIterateResult to be filled.
+ *
+ * Pages are guaranteed to be delivered in numerical order.  tbmres->blockno is
+ * set to InvalidBlockNumber when there are no more pages to scan. If
+ * tbmres->ntuples < 0, then the bitmap is "lossy" and failed to remember the
+ * exact tuples to look at on this page --- the caller must examine all tuples
+ * on the page and check if they meet the intended condition.  If
+ * tbmres->recheck is true, only the indicated tuples need be examined, but the
+ * condition must be rechecked anyway.  (For ease of testing, recheck is always
+ * set true when ntuples < 0.)
  */
-TBMIterateResult *
-tbm_private_iterate(TBMPrivateIterator *iterator)
+void
+tbm_private_iterate(TBMPrivateIterator *iterator, TBMIterateResult *tbmres)
 {
 	TIDBitmap  *tbm = iterator->tbm;
-	TBMIterateResult *output = &(iterator->output);
 
 	Assert(tbm->iterating == TBM_ITERATING_PRIVATE);
 
@@ -999,11 +998,11 @@ tbm_private_iterate(TBMPrivateIterator *iterator)
 			chunk_blockno < tbm->spages[iterator->spageptr]->blockno)
 		{
 			/* Return a lossy page indicator from the chunk */
-			output->blockno = chunk_blockno;
-			output->ntuples = -1;
-			output->recheck = true;
+			tbmres->blockno = chunk_blockno;
+			tbmres->ntuples = -1;
+			tbmres->recheck = true;
 			iterator->schunkbit++;
-			return output;
+			return;
 		}
 	}
 
@@ -1019,16 +1018,16 @@ tbm_private_iterate(TBMPrivateIterator *iterator)
 			page = tbm->spages[iterator->spageptr];
 
 		/* scan bitmap to extract individual offset numbers */
-		ntuples = tbm_extract_page_tuple(page, output);
-		output->blockno = page->blockno;
-		output->ntuples = ntuples;
-		output->recheck = page->recheck;
+		ntuples = tbm_extract_page_tuple(page, tbmres);
+		tbmres->blockno = page->blockno;
+		tbmres->ntuples = ntuples;
+		tbmres->recheck = page->recheck;
 		iterator->spageptr++;
-		return output;
+		return;
 	}
 
 	/* Nothing more in the bitmap */
-	return NULL;
+	tbmres->blockno = InvalidBlockNumber;
 }
 
 /*
@@ -1038,10 +1037,9 @@ tbm_private_iterate(TBMPrivateIterator *iterator)
  *	across multiple processes.  We need to acquire the iterator LWLock,
  *	before accessing the shared members.
  */
-TBMIterateResult *
-tbm_shared_iterate(TBMSharedIterator *iterator)
+void
+tbm_shared_iterate(TBMSharedIterator *iterator, TBMIterateResult *tbmres)
 {
-	TBMIterateResult *output = &iterator->output;
 	TBMSharedIteratorState *istate = iterator->state;
 	PagetableEntry *ptbase = NULL;
 	int		   *idxpages = NULL;
@@ -1092,13 +1090,13 @@ tbm_shared_iterate(TBMSharedIterator *iterator)
 			chunk_blockno < ptbase[idxpages[istate->spageptr]].blockno)
 		{
 			/* Return a lossy page indicator from the chunk */
-			output->blockno = chunk_blockno;
-			output->ntuples = -1;
-			output->recheck = true;
+			tbmres->blockno = chunk_blockno;
+			tbmres->ntuples = -1;
+			tbmres->recheck = true;
 			istate->schunkbit++;
 
 			LWLockRelease(&istate->lock);
-			return output;
+			return;
 		}
 	}
 
@@ -1108,21 +1106,21 @@ tbm_shared_iterate(TBMSharedIterator *iterator)
 		int			ntuples;
 
 		/* scan bitmap to extract individual offset numbers */
-		ntuples = tbm_extract_page_tuple(page, output);
-		output->blockno = page->blockno;
-		output->ntuples = ntuples;
-		output->recheck = page->recheck;
+		ntuples = tbm_extract_page_tuple(page, tbmres);
+		tbmres->blockno = page->blockno;
+		tbmres->ntuples = ntuples;
+		tbmres->recheck = page->recheck;
 		istate->spageptr++;
 
 		LWLockRelease(&istate->lock);
 
-		return output;
+		return;
 	}
 
 	LWLockRelease(&istate->lock);
 
 	/* Nothing more in the bitmap */
-	return NULL;
+	tbmres->blockno = InvalidBlockNumber;
 }
 
 /*
@@ -1598,13 +1596,14 @@ tbm_end_iterate(TBMIterator *iterator)
 /*
  * Get the next TBMIterateResult from the shared or private bitmap iterator.
  */
-TBMIterateResult *
-tbm_iterate(TBMIterator *iterator)
+void
+tbm_iterate(TBMIterator *iterator, TBMIterateResult *tbmres)
 {
 	Assert(iterator);
+	Assert(tbmres);
 
 	if (iterator->shared)
-		return tbm_shared_iterate(iterator->i.shared_iterator);
+		return tbm_shared_iterate(iterator->i.shared_iterator, tbmres);
 	else
-		return tbm_private_iterate(iterator->i.private_iterator);
+		return tbm_private_iterate(iterator->i.private_iterator, tbmres);
 }
diff --git a/src/include/access/gin_private.h b/src/include/access/gin_private.h
index dcd1ae3fc34..a7071c4cbdc 100644
--- a/src/include/access/gin_private.h
+++ b/src/include/access/gin_private.h
@@ -353,7 +353,7 @@ typedef struct GinScanEntryData
 	/* for a partial-match or full-scan query, we accumulate all TIDs here */
 	TIDBitmap  *matchBitmap;
 	TBMPrivateIterator *matchIterator;
-	TBMIterateResult *matchResult;
+	TBMIterateResult matchResult;
 
 	/* used for Posting list and one page in Posting tree */
 	ItemPointerData *list;
diff --git a/src/include/nodes/tidbitmap.h b/src/include/nodes/tidbitmap.h
index b2e322508a2..f3956d5171e 100644
--- a/src/include/nodes/tidbitmap.h
+++ b/src/include/nodes/tidbitmap.h
@@ -86,8 +86,8 @@ extern bool tbm_is_empty(const TIDBitmap *tbm);
 
 extern TBMPrivateIterator *tbm_begin_private_iterate(TIDBitmap *tbm);
 extern dsa_pointer tbm_prepare_shared_iterate(TIDBitmap *tbm);
-extern TBMIterateResult *tbm_private_iterate(TBMPrivateIterator *iterator);
-extern TBMIterateResult *tbm_shared_iterate(TBMSharedIterator *iterator);
+extern void tbm_private_iterate(TBMPrivateIterator *iterator, TBMIterateResult *tbmres);
+extern void tbm_shared_iterate(TBMSharedIterator *iterator, TBMIterateResult *tbmres);
 extern void tbm_end_private_iterate(TBMPrivateIterator *iterator);
 extern void tbm_end_shared_iterate(TBMSharedIterator *iterator);
 extern TBMSharedIterator *tbm_attach_shared_iterate(dsa_area *dsa,
@@ -98,7 +98,7 @@ extern TBMIterator tbm_begin_iterate(TIDBitmap *tbm,
 									 dsa_area *dsa, dsa_pointer dsp);
 extern void tbm_end_iterate(TBMIterator *iterator);
 
-extern TBMIterateResult *tbm_iterate(TBMIterator *iterator);
+extern void tbm_iterate(TBMIterator *iterator, TBMIterateResult *tbmres);
 
 static inline bool
 tbm_exhausted(TBMIterator *iterator)
-- 
2.34.1