0001-Fix-handling-of-the-last-item-in-gtrgm_picksplit.patch

From 6c9250aec8e952556c7f58c76896d8ff08a03dce Mon Sep 17 00:00:00 2001
From: Alexander Korotkov <akorotkov@postgresql.org>
Date: Thu, 12 Nov 2020 06:16:30 +0300
Subject: [PATCH] Fix handling of the last item in gtrgm_picksplit()

Reported-by:
Bug:
Discussion:
Author:
Reviewed-by:
Tested-by:
Backpatch-through:
---
 contrib/pg_trgm/trgm_gist.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/contrib/pg_trgm/trgm_gist.c b/contrib/pg_trgm/trgm_gist.c
index 2a067306354..9c0ed6ed73a 100644
--- a/contrib/pg_trgm/trgm_gist.c
+++ b/contrib/pg_trgm/trgm_gist.c
@@ -786,7 +786,7 @@ Datum
 gtrgm_picksplit(PG_FUNCTION_ARGS)
 {
 	GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
-	OffsetNumber maxoff = entryvec->n - 2;
+	OffsetNumber maxoff = entryvec->n - 1;
 	GIST_SPLITVEC *v = (GIST_SPLITVEC *) PG_GETARG_POINTER(1);
 	int			siglen = GET_SIGLEN();
 	OffsetNumber k,
@@ -811,8 +811,8 @@ gtrgm_picksplit(PG_FUNCTION_ARGS)
 	SPLITCOST  *costvector;
 
 	/* cache the sign data for each existing item */
-	cache = (CACHESIGN *) palloc(sizeof(CACHESIGN) * (maxoff + 2));
-	cache_sign = palloc(siglen * (maxoff + 2));
+	cache = (CACHESIGN *) palloc(sizeof(CACHESIGN) * (maxoff + 1));
+	cache_sign = palloc(siglen * (maxoff + 1));
 
 	for (k = FirstOffsetNumber; k <= maxoff; k = OffsetNumberNext(k))
 		fillcache(&cache[k], GETENTRY(entryvec, k), &cache_sign[siglen * k],
@@ -841,7 +841,7 @@ gtrgm_picksplit(PG_FUNCTION_ARGS)
 	}
 
 	/* initialize the result vectors */
-	nbytes = (maxoff + 2) * sizeof(OffsetNumber);
+	nbytes = maxoff * sizeof(OffsetNumber);
 	v->spl_left = left = (OffsetNumber *) palloc(nbytes);
 	v->spl_right = right = (OffsetNumber *) palloc(nbytes);
 	v->spl_nleft = 0;
@@ -853,9 +853,6 @@ gtrgm_picksplit(PG_FUNCTION_ARGS)
 
 	union_l = GETSIGN(datum_l);
 	union_r = GETSIGN(datum_r);
-	maxoff = OffsetNumberNext(maxoff);
-	fillcache(&cache[maxoff], GETENTRY(entryvec, maxoff),
-			  &cache_sign[siglen * maxoff], siglen);
 
 	/* sort before ... */
 	costvector = (SPLITCOST *) palloc(sizeof(SPLITCOST) * maxoff);
@@ -944,7 +941,6 @@ gtrgm_picksplit(PG_FUNCTION_ARGS)
 		}
 	}
 
-	*right = *left = FirstOffsetNumber;
 	v->spl_ldatum = PointerGetDatum(datum_l);
 	v->spl_rdatum = PointerGetDatum(datum_r);
 
-- 
2.14.3