v3-0001-Allow-parallel-GIN-builds-to-allocate-large-chunk.patch

From a287cd4e711fba07029d873c9049010599616b6d Mon Sep 17 00:00:00 2001
From: Tomas Vondra <tomas@vondra.me>
Date: Sun, 26 Oct 2025 21:14:44 +0100
Subject: [PATCH v3 1/3] Allow parallel GIN builds to allocate large chunks

The parallel GIN builds used palloc/repalloc to maintain TID lists,
which with high maintance_work_mem values can lead to failures like

    ERROR:  invalid memory alloc request size 1113001620

The reason is that while merging intermediate worker data, we call
GinBufferStoreTuple() which coalesces the TID lists, and the result
may not fit into MaxAllocSize.

Fixed by allowing huge allocations when merging TID lists, including
an existing palloc call in ginMergeItemPointers().

Report by Greg Smith, investigation and fix by me. Batchpatched to 18,
where parallel GIN builds were introduced.

Reported-by: Gregory Smith <gregsmithpgsql@gmail.com>
Discussion: https://postgr.es/m/CAHLJuCWDwn-PE2BMZE4Kux7x5wWt_6RoWtA0mUQffEDLeZ6sfA@mail.gmail.com
Backpatch-through: 18
---
 src/backend/access/gin/gininsert.c      | 7 ++++---
 src/backend/access/gin/ginpostinglist.c | 3 ++-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/backend/access/gin/gininsert.c b/src/backend/access/gin/gininsert.c
index 3d71b442aa9..2355b96b351 100644
--- a/src/backend/access/gin/gininsert.c
+++ b/src/backend/access/gin/gininsert.c
@@ -1496,10 +1496,11 @@ GinBufferStoreTuple(GinBuffer *buffer, GinTuple *tup)
 		 * still pass 0 as number of elements in that array though.
 		 */
 		if (buffer->items == NULL)
-			buffer->items = palloc((buffer->nitems + tup->nitems) * sizeof(ItemPointerData));
+			buffer->items = palloc_extended((buffer->nitems + tup->nitems) * sizeof(ItemPointerData),
+											MCXT_ALLOC_HUGE);
 		else
-			buffer->items = repalloc(buffer->items,
-									 (buffer->nitems + tup->nitems) * sizeof(ItemPointerData));
+			buffer->items = repalloc_huge(buffer->items,
+										  (buffer->nitems + tup->nitems) * sizeof(ItemPointerData));
 
 		new = ginMergeItemPointers(&buffer->items[buffer->nfrozen], /* first unfrozen */
 								   (buffer->nitems - buffer->nfrozen),	/* num of unfrozen */
diff --git a/src/backend/access/gin/ginpostinglist.c b/src/backend/access/gin/ginpostinglist.c
index 48eadec87b0..4fe46135238 100644
--- a/src/backend/access/gin/ginpostinglist.c
+++ b/src/backend/access/gin/ginpostinglist.c
@@ -381,7 +381,8 @@ ginMergeItemPointers(ItemPointerData *a, uint32 na,
 {
 	ItemPointerData *dst;
 
-	dst = (ItemPointer) palloc((na + nb) * sizeof(ItemPointerData));
+	dst = (ItemPointer) palloc_extended((na + nb) * sizeof(ItemPointerData),
+										MCXT_ALLOC_HUGE);
 
 	/*
 	 * If the argument arrays don't overlap, we can just append them to each
-- 
2.51.0