diff --git a/src/backend/utils/adt/pg_lzcompress.c b/src/backend/utils/adt/pg_lzcompress.c
index 66c64c1..b4a8b8b 100644
--- a/src/backend/utils/adt/pg_lzcompress.c
+++ b/src/backend/utils/adt/pg_lzcompress.c
@@ -198,9 +198,9 @@
  */
 typedef struct PGLZ_HistEntry
 {
-	struct PGLZ_HistEntry *next;	/* links for my hash key's list */
-	struct PGLZ_HistEntry *prev;
-	int			hindex;			/* my current hash key */
+	int16		next;			/* links for my hash key's list */
+	int16		prev;
+	uint32		hindex;			/* my current hash key */
 	const char *pos;			/* my input position */
 } PGLZ_HistEntry;

@@ -241,9 +241,11 @@ const PGLZ_Strategy *const PGLZ_strategy_always = &strategy_always_data;
  * Statically allocated work arrays for history
  * ----------
  */
-static PGLZ_HistEntry *hist_start[PGLZ_HISTORY_LISTS];
-static PGLZ_HistEntry hist_entries[PGLZ_HISTORY_SIZE];
+static int16 hist_start[PGLZ_HISTORY_LISTS];
+static PGLZ_HistEntry hist_entries[PGLZ_HISTORY_SIZE + 1];

+/* Element 0 in hist_entries is unused, and means 'invalid'. */
+#define INVALID_ENTRY			0

 /* ----------
  * pglz_hist_idx -
@@ -279,25 +281,25 @@ static PGLZ_HistEntry hist_entries[PGLZ_HISTORY_SIZE];
 #define pglz_hist_add(_hs,_he,_hn,_recycle,_s,_e) \
 do {									\
 			int __hindex = pglz_hist_idx((_s),(_e));						\
-			PGLZ_HistEntry **__myhsp = &(_hs)[__hindex];					\
+			int16 *__myhsp = &(_hs)[__hindex];								\
 			PGLZ_HistEntry *__myhe = &(_he)[_hn];							\
 			if (_recycle) {													\
-				if (__myhe->prev == NULL)									\
+				if (__myhe->prev == INVALID_ENTRY)							\
 					(_hs)[__myhe->hindex] = __myhe->next;					\
 				else														\
-					__myhe->prev->next = __myhe->next;						\
-				if (__myhe->next != NULL)									\
-					__myhe->next->prev = __myhe->prev;						\
+					(_he)[__myhe->prev].next = __myhe->next;				\
+				if (__myhe->next != INVALID_ENTRY)							\
+					(_he)[__myhe->next].prev = __myhe->prev;				\
 			}																\
 			__myhe->next = *__myhsp;										\
-			__myhe->prev = NULL;											\
+			__myhe->prev = INVALID_ENTRY;									\
 			__myhe->hindex = __hindex;										\
 			__myhe->pos  = (_s);											\
-			if (*__myhsp != NULL)											\
-				(*__myhsp)->prev = __myhe;									\
-			*__myhsp = __myhe;												\
-			if (++(_hn) >= PGLZ_HISTORY_SIZE) {								\
-				(_hn) = 0;													\
+			if (*__myhsp != INVALID_ENTRY)									\
+				(_he)[(*__myhsp)].prev = _hn;								\
+			*__myhsp = _hn;													\
+			if (++(_hn) >= PGLZ_HISTORY_SIZE + 1) {							\
+				(_hn) = 1;													\
 				(_recycle) = true;											\
 			}																\
 } while (0)
@@ -372,19 +374,20 @@ do { \
  * ----------
  */
 static inline int
-pglz_find_match(PGLZ_HistEntry **hstart, const char *input, const char *end,
+pglz_find_match(int16 *hstart, const char *input, const char *end,
 				int *lenp, int *offp, int good_match, int good_drop)
 {
-	PGLZ_HistEntry *hent;
+	int16		hentno;
 	int32		len = 0;
 	int32		off = 0;

 	/*
 	 * Traverse the linked history list until a good enough match is found.
 	 */
-	hent = hstart[pglz_hist_idx(input, end)];
-	while (hent)
+	hentno = hstart[pglz_hist_idx(input, end)];
+	while (hentno != INVALID_ENTRY)
 	{
+		PGLZ_HistEntry *hent = &hist_entries[hentno];
 		const char *ip = input;
 		const char *hp = hent->pos;
 		int32		thisoff;
@@ -443,13 +446,13 @@ pglz_find_match(PGLZ_HistEntry **hstart, const char *input, const char *end,
 		/*
 		 * Advance to the next history entry
 		 */
-		hent = hent->next;
+		hentno = hent->next;

 		/*
 		 * Be happy with lesser good matches the more entries we visited. But
 		 * no point in doing calculation if we're at end of list.
 		 */
-		if (hent)
+		if (hentno != INVALID_ENTRY)
 		{
 			if (len >= good_match)
 				break;
@@ -484,7 +487,7 @@ pglz_compress(const char *source, int32 slen, PGLZ_Header *dest,
 {
 	unsigned char *bp = ((unsigned char *) dest) + sizeof(PGLZ_Header);
 	unsigned char *bstart = bp;
-	int			hist_next = 0;
+	int			hist_next = 1;
 	bool		hist_recycle = false;
 	const char *dp = source;
 	const char *dend = source + slen;