Re: eliminate xl_heap_visible to reduce WAL (and eventually set VM on-access)

[Peter Eisentraut]

On 20.11.25 18:19, Melanie Plageman wrote:
+       prstate->deadoffsets = (OffsetNumber *) presult->deadoffsets;

In your patch 
v22-0001-Split-heap_page_prune_and_freeze-into-helpers.patch, the 
assignment above casts away the const qualification of the function 
argument presult:

+static void
+prune_freeze_setup(PruneFreezeParams *params,
+                                  TransactionId new_relfrozen_xid,
+                                  MultiXactId new_relmin_mxid,
+                                  const PruneFreezeResult *presult,
+                                  PruneState *prstate)

(The cast is otherwise unnecessary, since the underlying type is the 
same on both sides.)

Since prstate->deadoffsets is in fact later modified, this makes the 
original const qualification invalid.

I suggest the attached patch to remove the faulty const qualification 
and the then-unnecessary cast.
From 336aa87add1a85aca84d8ca751c4187a08aa9d7f Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pe...@eisentraut.org>
Date: Sat, 13 Dec 2025 14:45:08 +0100
Subject: [PATCH] Fix const qualification in prune_freeze_setup()

The const qualification of the presult argument is later cast away, so
it was not correct.
---
 src/backend/access/heap/pruneheap.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/heap/pruneheap.c 
b/src/backend/access/heap/pruneheap.c
index ca44225a10e..4eb49380b92 100644
--- a/src/backend/access/heap/pruneheap.c
+++ b/src/backend/access/heap/pruneheap.c
@@ -160,7 +160,7 @@ typedef struct
 static void prune_freeze_setup(PruneFreezeParams *params,
                                                           TransactionId 
*new_relfrozen_xid,
                                                           MultiXactId 
*new_relmin_mxid,
-                                                          const 
PruneFreezeResult *presult,
+                                                          PruneFreezeResult 
*presult,
                                                           PruneState *prstate);
 static void prune_freeze_plan(Oid reloid, Buffer buffer,
                                                          PruneState *prstate,
@@ -327,7 +327,7 @@ static void
 prune_freeze_setup(PruneFreezeParams *params,
                                   TransactionId *new_relfrozen_xid,
                                   MultiXactId *new_relmin_mxid,
-                                  const PruneFreezeResult *presult,
+                                  PruneFreezeResult *presult,
                                   PruneState *prstate)
 {
        /* Copy parameters to prstate */
@@ -382,7 +382,7 @@ prune_freeze_setup(PruneFreezeParams *params,
        prstate->recently_dead_tuples = 0;
        prstate->hastup = false;
        prstate->lpdead_items = 0;
-       prstate->deadoffsets = (OffsetNumber *) presult->deadoffsets;
+       prstate->deadoffsets = presult->deadoffsets;
        prstate->frz_conflict_horizon = InvalidTransactionId;
 
        /*
-- 
2.52.0