Rename and relocate freeze plan dedup routines.

Rename the heapam.c freeze plan deduplication routines added by commit
9e54059 to names that follow conventions for functions in heapam.c.
Also relocate the functions so that they're next to their caller, which
runs during original execution, when FREEZE_PAGE WAL records are built.

The routines were initially placed next to (and followed the naming
conventions of) conceptually related REDO routine code, but that scheme
turned out to be kind of jarring when considered in a wider context.

Author: Peter Geoghegan <pg@bowt.ie>
Reported-By: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20230109214308.icz26oqvt3k2274c@awork3.anarazel.de

Author: petergeoghegan

src/backend/access/heap/heapam.c

@@ -95,6 +95,9 @@ static void compute_new_xmax_infomask(TransactionId xmax, uint16 old_infomask,
 static TM_Result heap_lock_updated_tuple(Relation rel, HeapTuple tuple,
 										 ItemPointer ctid, TransactionId xid,
 										 LockTupleMode mode);
+static int	heap_log_freeze_plan(HeapTupleFreeze *tuples, int ntuples,
+								 xl_heap_freeze_plan *plans_out,
+								 OffsetNumber *offsets_out);
 static void GetMultiXactIdHintBits(MultiXactId multi, uint16 *new_infomask,
 								   uint16 *new_infomask2);
 static TransactionId MultiXactIdGetUpdateXid(TransactionId xmax,
@@ -111,9 +114,6 @@ static int	bottomup_sort_and_shrink(TM_IndexDeleteOp *delstate);
 static XLogRecPtr log_heap_new_cid(Relation relation, HeapTuple tup);
 static HeapTuple ExtractReplicaIdentity(Relation relation, HeapTuple tp, bool key_required,
 										bool *copy);
-static int	heap_xlog_freeze_plan(HeapTupleFreeze *tuples, int ntuples,
-								  xl_heap_freeze_plan *plans_out,
-								  OffsetNumber *offsets_out);
 
 
 /*
@@ -6868,7 +6868,7 @@ heap_freeze_execute_prepared(Relation rel, Buffer buffer,
 		XLogRecPtr	recptr;
 
 		/* Prepare deduplicated representation for use in WAL record */
-		nplans = heap_xlog_freeze_plan(tuples, ntuples, plans, offsets);
+		nplans = heap_log_freeze_plan(tuples, ntuples, plans, offsets);
 
 		xlrec.snapshotConflictHorizon = snapshotConflictHorizon;
 		xlrec.nplans = nplans;
@@ -6895,6 +6895,144 @@ heap_freeze_execute_prepared(Relation rel, Buffer buffer,
 	END_CRIT_SECTION();
 }
 
+/*
+ * Comparator used to deduplicate XLOG_HEAP2_FREEZE_PAGE freeze plans
+ */
+static int
+heap_log_freeze_cmp(const void *arg1, const void *arg2)
+{
+	HeapTupleFreeze *frz1 = (HeapTupleFreeze *) arg1;
+	HeapTupleFreeze *frz2 = (HeapTupleFreeze *) arg2;
+
+	if (frz1->xmax < frz2->xmax)
+		return -1;
+	else if (frz1->xmax > frz2->xmax)
+		return 1;
+
+	if (frz1->t_infomask2 < frz2->t_infomask2)
+		return -1;
+	else if (frz1->t_infomask2 > frz2->t_infomask2)
+		return 1;
+
+	if (frz1->t_infomask < frz2->t_infomask)
+		return -1;
+	else if (frz1->t_infomask > frz2->t_infomask)
+		return 1;
+
+	if (frz1->frzflags < frz2->frzflags)
+		return -1;
+	else if (frz1->frzflags > frz2->frzflags)
+		return 1;
+
+	/*
+	 * heap_log_freeze_eq would consider these tuple-wise plans to be equal.
+	 * (So the tuples will share a single canonical freeze plan.)
+	 *
+	 * We tiebreak on page offset number to keep each freeze plan's page
+	 * offset number array individually sorted. (Unnecessary, but be tidy.)
+	 */
+	if (frz1->offset < frz2->offset)
+		return -1;
+	else if (frz1->offset > frz2->offset)
+		return 1;
+
+	Assert(false);
+	return 0;
+}
+
+/*
+ * Compare fields that describe actions required to freeze tuple with caller's
+ * open plan.  If everything matches then the frz tuple plan is equivalent to
+ * caller's plan.
+ */
+static inline bool
+heap_log_freeze_eq(xl_heap_freeze_plan *plan, HeapTupleFreeze *frz)
+{
+	if (plan->xmax == frz->xmax &&
+		plan->t_infomask2 == frz->t_infomask2 &&
+		plan->t_infomask == frz->t_infomask &&
+		plan->frzflags == frz->frzflags)
+		return true;
+
+	/* Caller must call heap_log_freeze_new_plan again for frz */
+	return false;
+}
+
+/*
+ * Start new plan initialized using tuple-level actions.  At least one tuple
+ * will have steps required to freeze described by caller's plan during REDO.
+ */
+static inline void
+heap_log_freeze_new_plan(xl_heap_freeze_plan *plan, HeapTupleFreeze *frz)
+{
+	plan->xmax = frz->xmax;
+	plan->t_infomask2 = frz->t_infomask2;
+	plan->t_infomask = frz->t_infomask;
+	plan->frzflags = frz->frzflags;
+	plan->ntuples = 1;			/* for now */
+}
+
+/*
+ * Deduplicate tuple-based freeze plans so that each distinct set of
+ * processing steps is only stored once in XLOG_HEAP2_FREEZE_PAGE records.
+ * Called during original execution of freezing (for logged relations).
+ *
+ * Return value is number of plans set in *plans_out for caller.  Also writes
+ * an array of offset numbers into *offsets_out output argument for caller
+ * (actually there is one array per freeze plan, but that's not of immediate
+ * concern to our caller).
+ */
+static int
+heap_log_freeze_plan(HeapTupleFreeze *tuples, int ntuples,
+					 xl_heap_freeze_plan *plans_out,
+					 OffsetNumber *offsets_out)
+{
+	int			nplans = 0;
+
+	/* Sort tuple-based freeze plans in the order required to deduplicate */
+	qsort(tuples, ntuples, sizeof(HeapTupleFreeze), heap_log_freeze_cmp);
+
+	for (int i = 0; i < ntuples; i++)
+	{
+		HeapTupleFreeze *frz = tuples + i;
+
+		if (i == 0)
+		{
+			/* New canonical freeze plan starting with first tup */
+			heap_log_freeze_new_plan(plans_out, frz);
+			nplans++;
+		}
+		else if (heap_log_freeze_eq(plans_out, frz))
+		{
+			/* tup matches open canonical plan -- include tup in it */
+			Assert(offsets_out[i - 1] < frz->offset);
+			plans_out->ntuples++;
+		}
+		else
+		{
+			/* Tup doesn't match current plan -- done with it now */
+			plans_out++;
+
+			/* New canonical freeze plan starting with this tup */
+			heap_log_freeze_new_plan(plans_out, frz);
+			nplans++;
+		}
+
+		/*
+		 * Save page offset number in dedicated buffer in passing.
+		 *
+		 * REDO routine relies on the record's offset numbers array grouping
+		 * offset numbers by freeze plan.  The sort order within each grouping
+		 * is ascending offset number order, just to keep things tidy.
+		 */
+		offsets_out[i] = frz->offset;
+	}
+
+	Assert(nplans > 0 && nplans <= ntuples);
+
+	return nplans;
+}
+
 /*
  * heap_freeze_tuple
  *		Freeze tuple in place, without WAL logging.
@@ -9015,144 +9153,6 @@ heap_xlog_visible(XLogReaderState *record)
 		UnlockReleaseBuffer(vmbuffer);
 }
 
-/*
- * Comparator used to deduplicate XLOG_HEAP2_FREEZE_PAGE freeze plans
- */
-static int
-heap_xlog_freeze_cmp(const void *arg1, const void *arg2)
-{
-	HeapTupleFreeze *frz1 = (HeapTupleFreeze *) arg1;
-	HeapTupleFreeze *frz2 = (HeapTupleFreeze *) arg2;
-
-	if (frz1->xmax < frz2->xmax)
-		return -1;
-	else if (frz1->xmax > frz2->xmax)
-		return 1;
-
-	if (frz1->t_infomask2 < frz2->t_infomask2)
-		return -1;
-	else if (frz1->t_infomask2 > frz2->t_infomask2)
-		return 1;
-
-	if (frz1->t_infomask < frz2->t_infomask)
-		return -1;
-	else if (frz1->t_infomask > frz2->t_infomask)
-		return 1;
-
-	if (frz1->frzflags < frz2->frzflags)
-		return -1;
-	else if (frz1->frzflags > frz2->frzflags)
-		return 1;
-
-	/*
-	 * heap_xlog_freeze_eq would consider these tuple-wise plans to be equal.
-	 * (So the tuples will share a single canonical freeze plan.)
-	 *
-	 * We tiebreak on page offset number to keep each freeze plan's page
-	 * offset number array individually sorted. (Unnecessary, but be tidy.)
-	 */
-	if (frz1->offset < frz2->offset)
-		return -1;
-	else if (frz1->offset > frz2->offset)
-		return 1;
-
-	Assert(false);
-	return 0;
-}
-
-/*
- * Compare fields that describe actions required to freeze tuple with caller's
- * open plan.  If everything matches then the frz tuple plan is equivalent to
- * caller's plan.
- */
-static inline bool
-heap_xlog_freeze_eq(xl_heap_freeze_plan *plan, HeapTupleFreeze *frz)
-{
-	if (plan->xmax == frz->xmax &&
-		plan->t_infomask2 == frz->t_infomask2 &&
-		plan->t_infomask == frz->t_infomask &&
-		plan->frzflags == frz->frzflags)
-		return true;
-
-	/* Caller must call heap_xlog_new_freeze_plan again for frz */
-	return false;
-}
-
-/*
- * Start new plan initialized using tuple-level actions.  At least one tuple
- * will have steps required to freeze described by caller's plan during REDO.
- */
-static inline void
-heap_xlog_new_freeze_plan(xl_heap_freeze_plan *plan, HeapTupleFreeze *frz)
-{
-	plan->xmax = frz->xmax;
-	plan->t_infomask2 = frz->t_infomask2;
-	plan->t_infomask = frz->t_infomask;
-	plan->frzflags = frz->frzflags;
-	plan->ntuples = 1;			/* for now */
-}
-
-/*
- * Deduplicate tuple-based freeze plans so that each distinct set of
- * processing steps is only stored once in XLOG_HEAP2_FREEZE_PAGE records.
- * Called during original execution of freezing (for logged relations).
- *
- * Return value is number of plans set in *plans_out for caller.  Also writes
- * an array of offset numbers into *offsets_out output argument for caller
- * (actually there is one array per freeze plan, but that's not of immediate
- * concern to our caller).
- */
-static int
-heap_xlog_freeze_plan(HeapTupleFreeze *tuples, int ntuples,
-					  xl_heap_freeze_plan *plans_out,
-					  OffsetNumber *offsets_out)
-{
-	int			nplans = 0;
-
-	/* Sort tuple-based freeze plans in the order required to deduplicate */
-	qsort(tuples, ntuples, sizeof(HeapTupleFreeze), heap_xlog_freeze_cmp);
-
-	for (int i = 0; i < ntuples; i++)
-	{
-		HeapTupleFreeze *frz = tuples + i;
-
-		if (i == 0)
-		{
-			/* New canonical freeze plan starting with first tup */
-			heap_xlog_new_freeze_plan(plans_out, frz);
-			nplans++;
-		}
-		else if (heap_xlog_freeze_eq(plans_out, frz))
-		{
-			/* tup matches open canonical plan -- include tup in it */
-			Assert(offsets_out[i - 1] < frz->offset);
-			plans_out->ntuples++;
-		}
-		else
-		{
-			/* Tup doesn't match current plan -- done with it now */
-			plans_out++;
-
-			/* New canonical freeze plan starting with this tup */
-			heap_xlog_new_freeze_plan(plans_out, frz);
-			nplans++;
-		}
-
-		/*
-		 * Save page offset number in dedicated buffer in passing.
-		 *
-		 * REDO routine relies on the record's offset numbers array grouping
-		 * offset numbers by freeze plan.  The sort order within each grouping
-		 * is ascending offset number order, just to keep things tidy.
-		 */
-		offsets_out[i] = frz->offset;
-	}
-
-	Assert(nplans > 0 && nplans <= ntuples);
-
-	return nplans;
-}
-
 /*
  * Replay XLOG_HEAP2_FREEZE_PAGE records
  */
@@ -9189,21 +9189,19 @@ heap_xlog_freeze_page(XLogReaderState *record)
 									 sizeof(xl_heap_freeze_plan)));
 		for (int p = 0; p < xlrec->nplans; p++)
 		{
-			xl_heap_freeze_plan plan;
 			HeapTupleFreeze frz;
 
 			/*
 			 * Convert freeze plan representation from WAL record into
 			 * per-tuple format used by heap_execute_freeze_tuple
 			 */
-			memcpy(&plan, &plans[p], sizeof(xl_heap_freeze_plan));
-			frz.xmax = plan.xmax;
-			frz.t_infomask2 = plan.t_infomask2;
-			frz.t_infomask = plan.t_infomask;
-			frz.frzflags = plan.frzflags;
+			frz.xmax = plans[p].xmax;
+			frz.t_infomask2 = plans[p].t_infomask2;
+			frz.t_infomask = plans[p].t_infomask;
+			frz.frzflags = plans[p].frzflags;
 			frz.offset = InvalidOffsetNumber;	/* unused, but be tidy */
 
-			for (int i = 0; i < plan.ntuples; i++)
+			for (int i = 0; i < plans[p].ntuples; i++)
 			{
 				OffsetNumber offset = offsets[curoff++];
 				ItemId		lp;