0001-WIP-Prevent-overflows-for-BRIN-page-ranges.patch

From cf53c109c73cfa9264df71763e9ec5712f1c1f7f Mon Sep 17 00:00:00 2001
From: Tomas Vondra <tomas@2ndquadrant.com>
Date: Thu, 7 Dec 2023 15:07:04 +0100
Subject: [PATCH] WIP: Prevent overflows for BRIN page ranges

Introduces remove brin_next_range that checks if blkno overflows, and
instead sets it to InvalidBlockNumber.
---
 src/backend/access/brin/brin.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/brin/brin.c b/src/backend/access/brin/brin.c
index 23f081389b2..1952142d050 100644
--- a/src/backend/access/brin/brin.c
+++ b/src/backend/access/brin/brin.c
@@ -227,6 +227,7 @@ static bool add_values_to_range(Relation idxRel, BrinDesc *bdesc,
 static bool check_null_keys(BrinValues *bval, ScanKey *nullkeys, int nnullkeys);
 static void brin_fill_empty_ranges(BrinBuildState *state,
 								   BlockNumber prevRange, BlockNumber maxRange);
+static BlockNumber brin_next_range(BrinBuildState *state, BlockNumber blkno);
 
 /* parallel index builds */
 static void _brin_begin_parallel(BrinBuildState *buildstate, Relation heap, Relation index,
@@ -2935,7 +2936,7 @@ brin_fill_empty_ranges(BrinBuildState *state,
 	 * If we already summarized some ranges, we need to start with the next
 	 * one. Otherwise start from the first range of the table.
 	 */
-	blkno = (prevRange == InvalidBlockNumber) ? 0 : (prevRange + state->bs_pagesPerRange);
+	blkno = (prevRange == InvalidBlockNumber) ? 0 : brin_next_range(state, prevRange);
 
 	/* Generate empty ranges until we hit the next non-empty range. */
 	while (blkno < nextRange)
@@ -2948,6 +2949,18 @@ brin_fill_empty_ranges(BrinBuildState *state,
 					  blkno, state->bs_emptyTuple, state->bs_emptyTupleLen);
 
 		/* try next page range */
-		blkno += state->bs_pagesPerRange;
+		blkno = brin_next_range(state, blkno);
 	}
 }
+
+static BlockNumber
+brin_next_range(BrinBuildState *state, BlockNumber blkno)
+{
+	BlockNumber ret = (blkno + state->bs_pagesPerRange);
+
+	/* overflow */
+	if (ret < blkno)
+		ret = InvalidBlockNumber;
+
+	return ret;
+}
-- 
2.41.0