v22b-0006-Add-common-interface-for-TBMIterators.patch

From 90551a3422285d9c1207256e8f90dd5e8d753d29 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Sat, 6 Apr 2024 12:41:05 -0400
Subject: [PATCH v22b 06/29] Add common interface for TBMIterators

Add and use TBMSerialIterator, which replaces the current TBMIterator
for serial use cases, and repurpose TBMIterator to be a unified
interface for both the serial and parallel TID Bitmap iterator
interfaces. This encapsulation simplifies call sites for callers
supporting both parallel and serial TID Bitmap access. TBMIterator is
not yet used in this commit.

Author: Melanie Plageman
Discussion: https://postgr.es/m/CAAKRu_ZwCwWFeL_H3ia26bP2e7HiKLWt0ZmGXPVwPO6uXq0vaA%40mail.gmail.com
---
 src/backend/access/gin/ginget.c           |   8 +-
 src/backend/access/gin/ginscan.c          |   2 +-
 src/backend/access/heap/heapam_handler.c  |   2 +-
 src/backend/executor/nodeBitmapHeapscan.c |  22 ++---
 src/backend/nodes/tidbitmap.c             | 102 +++++++++++++++++-----
 src/include/access/gin_private.h          |   2 +-
 src/include/access/relscan.h              |   4 +-
 src/include/access/tableam.h              |   4 +-
 src/include/nodes/execnodes.h             |   2 +-
 src/include/nodes/tidbitmap.h             |  27 ++++--
 src/tools/pgindent/typedefs.list          |   1 +
 11 files changed, 126 insertions(+), 50 deletions(-)

diff --git a/src/backend/access/gin/ginget.c b/src/backend/access/gin/ginget.c
index 0b4f2ebadb6..9c53ca19f06 100644
--- a/src/backend/access/gin/ginget.c
+++ b/src/backend/access/gin/ginget.c
@@ -373,7 +373,7 @@ restartScanEntry:
 			if (entry->matchBitmap)
 			{
 				if (entry->matchIterator)
-					tbm_end_iterate(entry->matchIterator);
+					tbm_end_private_iterate(entry->matchIterator);
 				entry->matchIterator = NULL;
 				tbm_free(entry->matchBitmap);
 				entry->matchBitmap = NULL;
@@ -385,7 +385,7 @@ restartScanEntry:
 
 		if (entry->matchBitmap && !tbm_is_empty(entry->matchBitmap))
 		{
-			entry->matchIterator = tbm_begin_iterate(entry->matchBitmap);
+			entry->matchIterator = tbm_begin_private_iterate(entry->matchBitmap);
 			entry->isFinished = false;
 		}
 	}
@@ -832,12 +832,12 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
 				   (ItemPointerIsLossyPage(&advancePast) &&
 					entry->matchResult->blockno == advancePastBlk))
 			{
-				entry->matchResult = tbm_iterate(entry->matchIterator);
+				entry->matchResult = tbm_private_iterate(entry->matchIterator);
 
 				if (entry->matchResult == NULL)
 				{
 					ItemPointerSetInvalid(&entry->curItem);
-					tbm_end_iterate(entry->matchIterator);
+					tbm_end_private_iterate(entry->matchIterator);
 					entry->matchIterator = NULL;
 					entry->isFinished = true;
 					break;
diff --git a/src/backend/access/gin/ginscan.c b/src/backend/access/gin/ginscan.c
index af24d38544e..5b9a0eaea73 100644
--- a/src/backend/access/gin/ginscan.c
+++ b/src/backend/access/gin/ginscan.c
@@ -246,7 +246,7 @@ ginFreeScanKeys(GinScanOpaque so)
 		if (entry->list)
 			pfree(entry->list);
 		if (entry->matchIterator)
-			tbm_end_iterate(entry->matchIterator);
+			tbm_end_private_iterate(entry->matchIterator);
 		if (entry->matchBitmap)
 			tbm_free(entry->matchBitmap);
 	}
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index e92c44d9049..9a097f1ce76 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -2143,7 +2143,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
 		if (scan->shared_tbmiterator)
 			tbmres = tbm_shared_iterate(scan->shared_tbmiterator);
 		else
-			tbmres = tbm_iterate(scan->tbmiterator);
+			tbmres = tbm_private_iterate(scan->tbmiterator);
 
 		if (tbmres == NULL)
 			return false;
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index 6d7ef9ced19..12a85f0e72f 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -96,7 +96,7 @@ BitmapHeapNext(BitmapHeapScanState *node)
 	 */
 	if (!node->initialized)
 	{
-		TBMIterator *tbmiterator = NULL;
+		TBMPrivateIterator *tbmiterator = NULL;
 		TBMSharedIterator *shared_tbmiterator = NULL;
 
 		if (!pstate)
@@ -107,12 +107,12 @@ BitmapHeapNext(BitmapHeapScanState *node)
 				elog(ERROR, "unrecognized result from subplan");
 
 			node->tbm = tbm;
-			tbmiterator = tbm_begin_iterate(tbm);
+			tbmiterator = tbm_begin_private_iterate(tbm);
 
 #ifdef USE_PREFETCH
 			if (node->prefetch_maximum > 0)
 			{
-				node->prefetch_iterator = tbm_begin_iterate(tbm);
+				node->prefetch_iterator = tbm_begin_private_iterate(tbm);
 				node->prefetch_pages = 0;
 				node->prefetch_target = -1;
 			}
@@ -289,7 +289,7 @@ new_page:
 			break;
 
 		/*
-		 * If serial, we can error out if the the prefetch block doesn't stay
+		 * If private, we can error out if the the prefetch block doesn't stay
 		 * ahead of the current block.
 		 */
 		if (node->pstate == NULL &&
@@ -338,7 +338,7 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node)
 
 	if (pstate == NULL)
 	{
-		TBMIterator *prefetch_iterator = node->prefetch_iterator;
+		TBMPrivateIterator *prefetch_iterator = node->prefetch_iterator;
 
 		if (node->prefetch_pages > 0)
 		{
@@ -348,7 +348,7 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node)
 		else if (prefetch_iterator)
 		{
 			/* Do not let the prefetch iterator get behind the main one */
-			tbmpre = tbm_iterate(prefetch_iterator);
+			tbmpre = tbm_private_iterate(prefetch_iterator);
 			node->pfblockno = tbmpre ? tbmpre->blockno : InvalidBlockNumber;
 		}
 		return;
@@ -451,19 +451,19 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
 
 	if (pstate == NULL)
 	{
-		TBMIterator *prefetch_iterator = node->prefetch_iterator;
+		TBMPrivateIterator *prefetch_iterator = node->prefetch_iterator;
 
 		if (prefetch_iterator)
 		{
 			while (node->prefetch_pages < node->prefetch_target)
 			{
-				TBMIterateResult *tbmpre = tbm_iterate(prefetch_iterator);
+				TBMIterateResult *tbmpre = tbm_private_iterate(prefetch_iterator);
 				bool		skip_fetch;
 
 				if (tbmpre == NULL)
 				{
 					/* No more pages to prefetch */
-					tbm_end_iterate(prefetch_iterator);
+					tbm_end_private_iterate(prefetch_iterator);
 					node->prefetch_iterator = NULL;
 					break;
 				}
@@ -590,7 +590,7 @@ ExecReScanBitmapHeapScan(BitmapHeapScanState *node)
 
 	/* release bitmaps and buffers if any */
 	if (node->prefetch_iterator)
-		tbm_end_iterate(node->prefetch_iterator);
+		tbm_end_private_iterate(node->prefetch_iterator);
 	if (node->shared_prefetch_iterator)
 		tbm_end_shared_iterate(node->shared_prefetch_iterator);
 	if (node->tbm)
@@ -646,7 +646,7 @@ ExecEndBitmapHeapScan(BitmapHeapScanState *node)
 	 * release bitmaps and buffers if any
 	 */
 	if (node->prefetch_iterator)
-		tbm_end_iterate(node->prefetch_iterator);
+		tbm_end_private_iterate(node->prefetch_iterator);
 	if (node->tbm)
 		tbm_free(node->tbm);
 	if (node->shared_prefetch_iterator)
diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
index e8ab5d78fcc..6d1fbcb03e9 100644
--- a/src/backend/nodes/tidbitmap.c
+++ b/src/backend/nodes/tidbitmap.c
@@ -170,12 +170,12 @@ struct TIDBitmap
 };
 
 /*
- * When iterating over a bitmap in sorted order, a TBMIterator is used to
- * track our progress.  There can be several iterators scanning the same
- * bitmap concurrently.  Note that the bitmap becomes read-only as soon as
- * any iterator is created.
+ * When iterating over a backend-local bitmap in sorted order, a
+ * TBMPrivateIterator is used to track our progress.  There can be several
+ * iterators scanning the same bitmap concurrently.  Note that the bitmap
+ * becomes read-only as soon as any iterator is created.
  */
-struct TBMIterator
+struct TBMPrivateIterator
 {
 	TIDBitmap  *tbm;			/* TIDBitmap we're iterating over */
 	int			spageptr;		/* next spages index */
@@ -213,8 +213,8 @@ typedef struct PTIterationArray
 } PTIterationArray;
 
 /*
- * same as TBMIterator, but it is used for joint iteration, therefore this
- * also holds a reference to the shared state.
+ * same as TBMPrivateIterator, but it is used for joint iteration, therefore
+ * this also holds a reference to the shared state.
  */
 struct TBMSharedIterator
 {
@@ -673,31 +673,31 @@ tbm_is_empty(const TIDBitmap *tbm)
 }
 
 /*
- * tbm_begin_iterate - prepare to iterate through a TIDBitmap
+ * tbm_begin_private_iterate - prepare to iterate through a TIDBitmap
  *
- * The TBMIterator struct is created in the caller's memory context.
- * For a clean shutdown of the iteration, call tbm_end_iterate; but it's
- * okay to just allow the memory context to be released, too.  It is caller's
- * responsibility not to touch the TBMIterator anymore once the TIDBitmap
+ * The TBMPrivateIterator struct is created in the caller's memory context. For
+ * a clean shutdown of the iteration, call tbm_end_iterate; but it's okay to
+ * just allow the memory context to be released, too.  It is caller's
+ * responsibility not to touch the TBMPrivateIterator anymore once the TIDBitmap
  * is freed.
  *
  * NB: after this is called, it is no longer allowed to modify the contents
  * of the bitmap.  However, you can call this multiple times to scan the
  * contents repeatedly, including parallel scans.
  */
-TBMIterator *
-tbm_begin_iterate(TIDBitmap *tbm)
+TBMPrivateIterator *
+tbm_begin_private_iterate(TIDBitmap *tbm)
 {
-	TBMIterator *iterator;
+	TBMPrivateIterator *iterator;
 
 	Assert(tbm->iterating != TBM_ITERATING_SHARED);
 
 	/*
-	 * Create the TBMIterator struct, with enough trailing space to serve the
-	 * needs of the TBMIterateResult sub-struct.
+	 * Create the TBMPrivateIterator struct, with enough trailing space to
+	 * serve the needs of the TBMIterateResult sub-struct.
 	 */
-	iterator = (TBMIterator *) palloc(sizeof(TBMIterator) +
-									  MAX_TUPLES_PER_PAGE * sizeof(OffsetNumber));
+	iterator = (TBMPrivateIterator *) palloc(sizeof(TBMPrivateIterator) +
+											 MAX_TUPLES_PER_PAGE * sizeof(OffsetNumber));
 	iterator->tbm = tbm;
 
 	/*
@@ -956,7 +956,7 @@ tbm_advance_schunkbit(PagetableEntry *chunk, int *schunkbitp)
 }
 
 /*
- * tbm_iterate - scan through next page of a TIDBitmap
+ * 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
@@ -968,7 +968,7 @@ tbm_advance_schunkbit(PagetableEntry *chunk, int *schunkbitp)
  * testing, recheck is always set true when ntuples < 0.)
  */
 TBMIterateResult *
-tbm_iterate(TBMIterator *iterator)
+tbm_private_iterate(TBMPrivateIterator *iterator)
 {
 	TIDBitmap  *tbm = iterator->tbm;
 	TBMIterateResult *output = &(iterator->output);
@@ -1143,7 +1143,7 @@ tbm_shared_iterate(TBMSharedIterator *iterator)
  * bitmap to return to read/write status when there are no more iterators.)
  */
 void
-tbm_end_iterate(TBMIterator *iterator)
+tbm_end_private_iterate(TBMPrivateIterator *iterator)
 {
 	pfree(iterator);
 }
@@ -1556,3 +1556,61 @@ tbm_calculate_entries(double maxbytes)
 
 	return nbuckets;
 }
+
+/*
+ * Start iteration on a shared or non-shared bitmap iterator. Note that tbm
+ * will only be provided by private BitmapHeapScan callers. dsa and dsp will
+ * only be provided by parallel BitmapHeapScan callers. For shared callers, one
+ * process must already have called tbm_prepare_shared_iterate() to create and
+ * set up the TBMSharedIteratorState. The TBMIterator is passed by reference to
+ * accommodate callers who would like to allocate it inside an existing struct.
+ */
+void
+tbm_begin_iterate(TBMIterator *iterator, TIDBitmap *tbm,
+				  dsa_area *dsa, dsa_pointer dsp)
+{
+	Assert(iterator);
+
+	iterator->private = NULL;
+	iterator->parallel = NULL;
+	iterator->exhausted = false;
+
+	/* Allocate a private iterator and attach the shared state to it */
+	if (DsaPointerIsValid(dsp))
+		iterator->parallel = tbm_attach_shared_iterate(dsa, dsp);
+	else
+		iterator->private = tbm_begin_private_iterate(tbm);
+}
+
+/*
+ * Clean up shared or non-shared bitmap iterator.
+ */
+void
+tbm_end_iterate(TBMIterator *iterator)
+{
+	Assert(iterator);
+
+	if (iterator->private)
+		tbm_end_private_iterate(iterator->private);
+	else if (iterator->parallel)
+		tbm_end_shared_iterate(iterator->parallel);
+
+	iterator->private = NULL;
+	iterator->parallel = NULL;
+	iterator->exhausted = true;
+}
+
+/*
+ * Get the next TBMIterateResult from the shared or non-shared bitmap iterator.
+ */
+TBMIterateResult *
+tbm_iterate(TBMIterator *iterator)
+{
+	Assert(iterator);
+	Assert(!iterator->exhausted);
+
+	if (iterator->private)
+		return tbm_private_iterate(iterator->private);
+	else
+		return tbm_shared_iterate(iterator->parallel);
+}
diff --git a/src/include/access/gin_private.h b/src/include/access/gin_private.h
index 3013a44bae1..78800509367 100644
--- a/src/include/access/gin_private.h
+++ b/src/include/access/gin_private.h
@@ -352,7 +352,7 @@ typedef struct GinScanEntryData
 
 	/* for a partial-match or full-scan query, we accumulate all TIDs here */
 	TIDBitmap  *matchBitmap;
-	TBMIterator *matchIterator;
+	TBMPrivateIterator *matchIterator;
 	TBMIterateResult *matchResult;
 
 	/* used for Posting list and one page in Posting tree */
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 024dc08c420..159921ffb50 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -24,7 +24,7 @@
 
 struct ParallelTableScanDescData;
 
-struct TBMIterator;
+struct TBMPrivateIterator;
 struct TBMSharedIterator;
 
 /*
@@ -40,7 +40,7 @@ typedef struct TableScanDescData
 	struct ScanKeyData *rs_key; /* array of scan key descriptors */
 
 	/* Iterators for Bitmap Table Scans */
-	struct TBMIterator *tbmiterator;
+	struct TBMPrivateIterator *tbmiterator;
 	struct TBMSharedIterator *shared_tbmiterator;
 
 	/* Range of ItemPointers for table_scan_getnextslot_tidrange() to scan. */
diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index c6a9fb34bd6..5dc39f85925 100644
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -1034,7 +1034,7 @@ table_endscan(TableScanDesc scan)
 
 		if (scan->tbmiterator)
 		{
-			tbm_end_iterate(scan->tbmiterator);
+			tbm_end_private_iterate(scan->tbmiterator);
 			scan->tbmiterator = NULL;
 		}
 	}
@@ -1060,7 +1060,7 @@ table_rescan(TableScanDesc scan,
 
 		if (scan->tbmiterator)
 		{
-			tbm_end_iterate(scan->tbmiterator);
+			tbm_end_private_iterate(scan->tbmiterator);
 			scan->tbmiterator = NULL;
 		}
 	}
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 0af7906a184..81447fea8c5 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1818,7 +1818,7 @@ typedef struct BitmapHeapScanState
 	Buffer		pvmbuffer;
 	long		exact_pages;
 	long		lossy_pages;
-	TBMIterator *prefetch_iterator;
+	TBMPrivateIterator *prefetch_iterator;
 	int			prefetch_pages;
 	int			prefetch_target;
 	int			prefetch_maximum;
diff --git a/src/include/nodes/tidbitmap.h b/src/include/nodes/tidbitmap.h
index 1945f0639bf..472c0b444bf 100644
--- a/src/include/nodes/tidbitmap.h
+++ b/src/include/nodes/tidbitmap.h
@@ -32,8 +32,8 @@
  */
 typedef struct TIDBitmap TIDBitmap;
 
-/* Likewise, TBMIterator is private */
-typedef struct TBMIterator TBMIterator;
+/* Likewise, TBMPrivateIterator is private */
+typedef struct TBMPrivateIterator TBMPrivateIterator;
 typedef struct TBMSharedIterator TBMSharedIterator;
 
 /* Result structure for tbm_iterate */
@@ -46,6 +46,17 @@ typedef struct TBMIterateResult
 	OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
 } TBMIterateResult;
 
+/*
+ * Callers with both private and parallel implementations can use this unified
+ * API.
+ */
+typedef struct TBMIterator
+{
+	TBMPrivateIterator *private;
+	TBMSharedIterator *parallel;
+	bool		exhausted;
+} TBMIterator;
+
 /* function prototypes in nodes/tidbitmap.c */
 
 extern TIDBitmap *tbm_create(long maxbytes, dsa_area *dsa);
@@ -62,14 +73,20 @@ extern void tbm_intersect(TIDBitmap *a, const TIDBitmap *b);
 
 extern bool tbm_is_empty(const TIDBitmap *tbm);
 
-extern TBMIterator *tbm_begin_iterate(TIDBitmap *tbm);
+extern TBMPrivateIterator *tbm_begin_private_iterate(TIDBitmap *tbm);
 extern dsa_pointer tbm_prepare_shared_iterate(TIDBitmap *tbm);
-extern TBMIterateResult *tbm_iterate(TBMIterator *iterator);
+extern TBMIterateResult *tbm_private_iterate(TBMPrivateIterator *iterator);
 extern TBMIterateResult *tbm_shared_iterate(TBMSharedIterator *iterator);
-extern void tbm_end_iterate(TBMIterator *iterator);
+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,
 													dsa_pointer dp);
 extern long tbm_calculate_entries(double maxbytes);
 
+extern void tbm_begin_iterate(TBMIterator *iterator, TIDBitmap *tbm,
+							  dsa_area *dsa, dsa_pointer dsp);
+extern void tbm_end_iterate(TBMIterator *iterator);
+extern TBMIterateResult *tbm_iterate(TBMIterator *iterator);
+
+
 #endif							/* TIDBITMAP_H */
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 61ad417cde6..757a9a3a41e 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2795,6 +2795,7 @@ TAR_MEMBER
 TBMIterateResult
 TBMIteratingState
 TBMIterator
+TBMPrivateIterator
 TBMSharedIterator
 TBMSharedIteratorState
 TBMStatus
-- 
2.45.2