Date: Wed, 24 Sep 2025 16:40:49 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: John Naylor <johncnaylorls@gmail.com>
Cc: "Chiranmoy.Bhattacharya@fujitsu.com" <Chiranmoy.Bhattacharya@fujitsu.com>,
	Tom Lane <tgl@sss.pgh.pa.us>, David Rowley <dgrowleyml@gmail.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>,
	"Devanga.Susmitha@fujitsu.com" <Devanga.Susmitha@fujitsu.com>,
	"Ragesh.Hajela@fujitsu.com" <Ragesh.Hajela@fujitsu.com>
Subject: Re: [PATCH] Hex-coding optimizations using SVE on ARM.
Message-ID: <aNRlYQoxTe8lOIEc@nathan>
References: 
 <OS9PR01MB15185B278E343A9BA5F0F6AB19700A@OS9PR01MB15185.jpnprd01.prod.outlook.com>
 <aMI-NF6KLc1x1pko@nathan>
 <OS9PR01MB1518513BA12A54A243342A2999709A@OS9PR01MB15185.jpnprd01.prod.outlook.com>
 <aMLpq9_wOz_tnHmm@nathan>
 <1787140.1757604720@sss.pgh.pa.us>
 <OS9PR01MB1518531C5857F194371EBCA329708A@OS9PR01MB15185.jpnprd01.prod.outlook.com>
 <aMSQ7ackQO-P7T3S@nathan>
 <aNGsGMowsTwd5_aY@nathan>
 <aNLu3mg3CV8VHZuv@nathan>
 <CANWCAZYXsJ54Qr8cwt+Yt15kku4C4-owu+KXPKyFpweN3L36jQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="9Pw58b1w01c2+m+5"
Content-Disposition: inline
In-Reply-To: 
 <CANWCAZYXsJ54Qr8cwt+Yt15kku4C4-owu+KXPKyFpweN3L36jQ@mail.gmail.com>
Archived-At: <https://www.postgresql.org/message-id/aNRlYQoxTe8lOIEc%40nathan>
Precedence: bulk


--9Pw58b1w01c2+m+5
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

On Wed, Sep 24, 2025 at 10:59:38AM +0700, John Naylor wrote:
> + if (unlikely(!hex_decode_simd_helper(srcv, &dstv1)))
> + break;
> 
> But if you really want to do something here, sprinkling "(un)likely"'s
> here seems like solving the wrong problem (even if they make any
> difference), since the early return is optimizing for exceptional
> conditions. In other places (cf. the UTF8 string verifier), we
> accumulate errors, and only if we have them at the end do we restart
> from the beginning with the slow error-checking path that can show the
> user the offending input.

I switched to an accumulator approach in v11.

> +vector8_sssub(const Vector8 v1, const Vector8 v2)
> 
> It's hard to parse "sss", so maybe we can borrow an Intel-ism and use
> "iss" for the signed case?

Done.

> +/* vector manipulation */
> +#ifndef USE_NO_SIMD
> +static inline Vector8 vector8_interleave_low(const Vector8 v1, const
> Vector8 v2);
> +static inline Vector8 vector8_interleave_high(const Vector8 v1, const
> Vector8 v2);
> +static inline Vector8 vector8_pack_16(const Vector8 v1, const Vector8 v2);
> +static inline Vector32 vector32_shift_left_nibble(const Vector32 v1);
> +static inline Vector32 vector32_shift_right_nibble(const Vector32 v1);
> +static inline Vector32 vector32_shift_right_byte(const Vector32 v1);
> 
> Do we need declarations for these? I recall that the existing
> declarations are there for functions that are also used internally.

Removed.

> The nibble/byte things are rather specific. Wouldn't it be more
> logical to expose the already-generic shift operations and let the
> caller say by how much? Or does the compiler refuse because the
> intrinsic doesn't get an immediate value? Some are like that, but I'm
> not sure about these. If so, that's annoying and I wonder if there's a
> workaround.

Yeah, the compiler refuses unless the value is an integer literal.  I
thought of using a switch statement to cover all the values used in-tree,
but I didn't like that, either.

> +vector8_has_ge(const Vector8 v, const uint8 c)
> +{
> +#ifdef USE_SSE2
> + Vector8 umax = _mm_max_epu8(v, vector8_broadcast(c));
> + Vector8 cmpe = _mm_cmpeq_epi8(umax, v);
> +
> + return vector8_is_highbit_set(cmpe);
> 
> We take pains to avoid signed comparison on unsigned input for the
> "le" case, and I don't see why it's okay here.

_mm_max_epu8() does unsigned comparisons, I think...

> Do the regression tests have long enough cases that test exceptional
> paths, like invalid bytes and embedded whitespace? If not, we need
> some.

Added.

I've also fixed builds on gcc/arm64, as discussed elsewhere [0].  Here are
the current numbers on my laptop:

                arm
    buf  | HEAD  | patch | % diff
  -------+-------+-------+--------
       2 |     4 |     4 |      0
       4 |     6 |     6 |      0
       8 |     8 |     8 |      0
      16 |    11 |    12 |     -9
      32 |    18 |     5 |     72
      64 |    38 |     6 |     84
     256 |   134 |    17 |     87
    1024 |   513 |    63 |     88
    4096 |  2081 |   262 |     87
   16384 |  8524 |  1058 |     88
   65536 | 34731 |  4224 |     88

[0] https://postgr.es/m/aNQtN89VW8z-yo3B%40nathan

-- 
nathan

--9Pw58b1w01c2+m+5
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v11-0001-Optimize-hex_encode-and-hex_decode-using-SIMD.patch

From b914ad69199bfbb4af95b97f83568401bc42f319 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathan@postgresql.org>
Date: Fri, 12 Sep 2025 15:51:55 -0500
Subject: [PATCH v11 1/1] Optimize hex_encode() and hex_decode() using SIMD.

---
 src/backend/utils/adt/encode.c        | 137 +++++++++++++++-
 src/include/port/simd.h               | 223 +++++++++++++++++++++++++-
 src/test/regress/expected/strings.out |  58 +++++++
 src/test/regress/sql/strings.sql      |  16 ++
 4 files changed, 424 insertions(+), 10 deletions(-)

diff --git a/src/backend/utils/adt/encode.c b/src/backend/utils/adt/encode.c
index 9a9c7e8da99..7ba92c2c481 100644
--- a/src/backend/utils/adt/encode.c
+++ b/src/backend/utils/adt/encode.c
@@ -16,6 +16,7 @@
 #include <ctype.h>
 
 #include "mb/pg_wchar.h"
+#include "port/simd.h"
 #include "utils/builtins.h"
 #include "utils/memutils.h"
 #include "varatt.h"
@@ -177,8 +178,8 @@ static const int8 hexlookup[128] = {
 	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 };
 
-uint64
-hex_encode(const char *src, size_t len, char *dst)
+static inline uint64
+hex_encode_scalar(const char *src, size_t len, char *dst)
 {
 	const char *end = src + len;
 
@@ -193,6 +194,57 @@ hex_encode(const char *src, size_t len, char *dst)
 	return (uint64) len * 2;
 }
 
+uint64
+hex_encode(const char *src, size_t len, char *dst)
+{
+#ifdef USE_NO_SIMD
+	return hex_encode_scalar(src, len, dst);
+#else
+	const uint64 tail_idx = len & ~(sizeof(Vector8) - 1);
+	uint64		i;
+
+	/*
+	 * This works by splitting the high and low nibbles of each byte into
+	 * separate vectors, adding the vectors to a mask that converts the
+	 * nibbles to their equivalent ASCII bytes, and interleaving those bytes
+	 * back together to form the final hex-encoded string.  It might be
+	 * possible to squeeze out a little more gain by manually unrolling the
+	 * loop, but for now we don't bother.
+	 */
+	for (i = 0; i < tail_idx; i += sizeof(Vector8))
+	{
+		Vector8		srcv;
+		Vector8		lo;
+		Vector8		hi;
+		Vector8		mask;
+
+		vector8_load(&srcv, (const uint8 *) &src[i]);
+
+		lo = vector8_and(srcv, vector8_broadcast(0x0f));
+		mask = vector8_gt(lo, vector8_broadcast(0x9));
+		mask = vector8_and(mask, vector8_broadcast('a' - '0' - 10));
+		mask = vector8_add(mask, vector8_broadcast('0'));
+		lo = vector8_add(lo, mask);
+
+		hi = vector8_and(srcv, vector8_broadcast(0xf0));
+		hi = vector8_shift_right_nibble(hi);
+		mask = vector8_gt(hi, vector8_broadcast(0x9));
+		mask = vector8_and(mask, vector8_broadcast('a' - '0' - 10));
+		mask = vector8_add(mask, vector8_broadcast('0'));
+		hi = vector8_add(hi, mask);
+
+		vector8_store((uint8 *) &dst[i * 2],
+					  vector8_interleave_low(hi, lo));
+		vector8_store((uint8 *) &dst[i * 2 + sizeof(Vector8)],
+					  vector8_interleave_high(hi, lo));
+	}
+
+	(void) hex_encode_scalar(src + i, len - i, dst + i * 2);
+
+	return (uint64) len * 2;
+#endif
+}
+
 static inline bool
 get_hex(const char *cp, char *out)
 {
@@ -213,8 +265,8 @@ hex_decode(const char *src, size_t len, char *dst)
 	return hex_decode_safe(src, len, dst, NULL);
 }
 
-uint64
-hex_decode_safe(const char *src, size_t len, char *dst, Node *escontext)
+static inline uint64
+hex_decode_safe_scalar(const char *src, size_t len, char *dst, Node *escontext)
 {
 	const char *s,
 			   *srcend;
@@ -254,6 +306,83 @@ hex_decode_safe(const char *src, size_t len, char *dst, Node *escontext)
 	return p - dst;
 }
 
+/*
+ * This helper converts each byte to its binary-equivalent nibble by
+ * subtraction and combines them to form the return bytes (separated by zero
+ * bytes).  Returns false if any input bytes are outside the expected ranges of
+ * ASCII values.  Otherwise, returns true.
+ */
+#ifndef USE_NO_SIMD
+static inline bool
+hex_decode_simd_helper(const Vector8 src, Vector8 *dst)
+{
+	Vector8		sub;
+	Vector8		msk;
+	bool		ret;
+
+	msk = vector8_gt(vector8_broadcast('9' + 1), src);
+	sub = vector8_and(msk, vector8_broadcast('0'));
+
+	msk = vector8_gt(src, vector8_broadcast('A' - 1));
+	msk = vector8_and(msk, vector8_broadcast('A' - 10));
+	sub = vector8_add(sub, msk);
+
+	msk = vector8_gt(src, vector8_broadcast('a' - 1));
+	msk = vector8_and(msk, vector8_broadcast('a' - 'A'));
+	sub = vector8_add(sub, msk);
+
+	*dst = vector8_issub(src, sub);
+	ret = !vector8_has_ge(*dst, 0x10);
+
+	msk = vector8_and(*dst, vector8_broadcast_u32(0xff00ff00));
+	msk = vector8_shift_right_byte(msk);
+	*dst = vector8_and(*dst, vector8_broadcast_u32(0x00ff00ff));
+	*dst = vector8_shift_left_nibble(*dst);
+	*dst = vector8_or(*dst, msk);
+	return ret;
+}
+#endif							/* ! USE_NO_SIMD */
+
+uint64
+hex_decode_safe(const char *src, size_t len, char *dst, Node *escontext)
+{
+#ifdef USE_NO_SIMD
+	return hex_decode_safe_scalar(src, len, dst, escontext);
+#else
+	const uint64 tail_idx = len & ~(sizeof(Vector8) * 2 - 1);
+	uint64		i;
+	bool		success = true;
+
+	/*
+	 * We must process 2 vectors at a time since the output will be half the
+	 * length of the input.
+	 */
+	for (i = 0; i < tail_idx; i += sizeof(Vector8) * 2)
+	{
+		Vector8		srcv;
+		Vector8		dstv1;
+		Vector8		dstv2;
+
+		vector8_load(&srcv, (const uint8 *) &src[i]);
+		success &= hex_decode_simd_helper(srcv, &dstv1);
+
+		vector8_load(&srcv, (const uint8 *) &src[i + sizeof(Vector8)]);
+		success &= hex_decode_simd_helper(srcv, &dstv2);
+
+		vector8_store((uint8 *) &dst[i / 2], vector8_pack_16(dstv1, dstv2));
+	}
+
+	/*
+	 * If something didn't look right in the vector path, try again in the
+	 * scalar path so that we can handle it correctly.
+	 */
+	if (unlikely(!success))
+		i = 0;
+
+	return i / 2 + hex_decode_safe_scalar(src + i, len - i, dst + i / 2, escontext);
+#endif
+}
+
 static uint64
 hex_enc_len(const char *src, size_t srclen)
 {
diff --git a/src/include/port/simd.h b/src/include/port/simd.h
index 97c5f353022..531d8b8b6d1 100644
--- a/src/include/port/simd.h
+++ b/src/include/port/simd.h
@@ -86,7 +86,7 @@ static inline uint32 vector8_highbit_mask(const Vector8 v);
 static inline Vector8 vector8_or(const Vector8 v1, const Vector8 v2);
 #ifndef USE_NO_SIMD
 static inline Vector32 vector32_or(const Vector32 v1, const Vector32 v2);
-static inline Vector8 vector8_ssub(const Vector8 v1, const Vector8 v2);
+static inline Vector8 vector8_ussub(const Vector8 v1, const Vector8 v2);
 #endif
 
 /*
@@ -128,6 +128,21 @@ vector32_load(Vector32 *v, const uint32 *s)
 }
 #endif							/* ! USE_NO_SIMD */
 
+/*
+ * Store a vector into the given memory address.
+ */
+#ifndef USE_NO_SIMD
+static inline void
+vector8_store(uint8 *s, Vector8 v)
+{
+#ifdef USE_SSE2
+	_mm_storeu_si128((Vector8 *) s, v);
+#elif defined(USE_NEON)
+	vst1q_u8(s, v);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
 /*
  * Create a vector with all elements set to the same value.
  */
@@ -155,6 +170,24 @@ vector32_broadcast(const uint32 c)
 }
 #endif							/* ! USE_NO_SIMD */
 
+/*
+ * Some compilers are picky about casts to the same underlying type, and others
+ * are picky about implicit conversions with vector types.  This function does
+ * the same thing as vector32_broadcast(), but it returns a Vector8 and is
+ * carefully crafted to avoid compiler indigestion.
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_broadcast_u32(const uint32 c)
+{
+#ifdef USE_SSE2
+	return vector32_broadcast(c);
+#elif defined(USE_NEON)
+	return (Vector8) vector32_broadcast(c);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
 /*
  * Return true if any elements in the vector are equal to the given scalar.
  */
@@ -257,13 +290,32 @@ vector8_has_le(const Vector8 v, const uint8 c)
 	 * NUL bytes.  This approach is a workaround for the lack of unsigned
 	 * comparison instructions on some architectures.
 	 */
-	result = vector8_has_zero(vector8_ssub(v, vector8_broadcast(c)));
+	result = vector8_has_zero(vector8_ussub(v, vector8_broadcast(c)));
 #endif
 
 	Assert(assert_result == result);
 	return result;
 }
 
+/*
+ * Returns true if any elements in the vector are greater than or equal to the
+ * given scalar.
+ */
+#ifndef USE_NO_SIMD
+static inline bool
+vector8_has_ge(const Vector8 v, const uint8 c)
+{
+#ifdef USE_SSE2
+	Vector8		umax = _mm_max_epu8(v, vector8_broadcast(c));
+	Vector8		cmpe = _mm_cmpeq_epi8(umax, v);
+
+	return vector8_is_highbit_set(cmpe);
+#elif defined(USE_NEON)
+	return vmaxvq_u8(v) >= c;
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
 /*
  * Return true if the high bit of any element is set
  */
@@ -358,15 +410,65 @@ vector32_or(const Vector32 v1, const Vector32 v2)
 }
 #endif							/* ! USE_NO_SIMD */
 
+/*
+ * Return the bitwise AND of the inputs.
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_and(const Vector8 v1, const Vector8 v2)
+{
+#ifdef USE_SSE2
+	return _mm_and_si128(v1, v2);
+#elif defined(USE_NEON)
+	return vandq_u8(v1, v2);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
+/*
+ * Return the result of adding the respective elements of the input vectors.
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_add(const Vector8 v1, const Vector8 v2)
+{
+#ifdef USE_SSE2
+	return _mm_add_epi8(v1, v2);
+#elif defined(USE_NEON)
+	return vaddq_u8(v1, v2);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
+/*
+ * Return the result of subtracting the respective elements of the input
+ * vectors using signed saturation (i.e., if the operation would yield a value
+ * less than -128, -128 is returned instead).  For more information on
+ * saturation arithmetic, see
+ * https://en.wikipedia.org/wiki/Saturation_arithmetic
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_issub(const Vector8 v1, const Vector8 v2)
+{
+#ifdef USE_SSE2
+	return _mm_subs_epi8(v1, v2);
+#elif defined(USE_NEON)
+	return (Vector8) vqsubq_s8((int8x16_t) v1, (int8x16_t) v2);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
 /*
  * Return the result of subtracting the respective elements of the input
- * vectors using saturation (i.e., if the operation would yield a value less
- * than zero, zero is returned instead).  For more information on saturation
- * arithmetic, see https://en.wikipedia.org/wiki/Saturation_arithmetic
+ * vectors using unsigned saturation (i.e., if the operation would yield a
+ * value less than zero, zero is returned instead).  For more information on
+ * saturation arithmetic, see
+ * https://en.wikipedia.org/wiki/Saturation_arithmetic
  */
 #ifndef USE_NO_SIMD
 static inline Vector8
-vector8_ssub(const Vector8 v1, const Vector8 v2)
+vector8_ussub(const Vector8 v1, const Vector8 v2)
 {
 #ifdef USE_SSE2
 	return _mm_subs_epu8(v1, v2);
@@ -404,6 +506,23 @@ vector32_eq(const Vector32 v1, const Vector32 v2)
 }
 #endif							/* ! USE_NO_SIMD */
 
+/*
+ * Return a vector with all bits set for each lane of v1 that is greater than
+ * the corresponding lane of v2.  NB: The comparison treats the elements as
+ * signed.
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_gt(const Vector8 v1, const Vector8 v2)
+{
+#ifdef USE_SSE2
+	return _mm_cmpgt_epi8(v1, v2);
+#elif defined(USE_NEON)
+	return vcgtq_s8((int8x16_t) v1, (int8x16_t) v2);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
 /*
  * Given two vectors, return a vector with the minimum element of each.
  */
@@ -419,4 +538,96 @@ vector8_min(const Vector8 v1, const Vector8 v2)
 }
 #endif							/* ! USE_NO_SIMD */
 
+/*
+ * Interleave elements of low halves of given vectors.
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_interleave_low(const Vector8 v1, const Vector8 v2)
+{
+#ifdef USE_SSE2
+	return _mm_unpacklo_epi8(v1, v2);
+#elif defined(USE_NEON)
+	return vzip1q_u8(v1, v2);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
+/*
+ * Interleave elements of high halves of given vectors.
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_interleave_high(const Vector8 v1, const Vector8 v2)
+{
+#ifdef USE_SSE2
+	return _mm_unpackhi_epi8(v1, v2);
+#elif defined(USE_NEON)
+	return vzip2q_u8(v1, v2);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
+/*
+ * Pack 16-bit elements in the given vectors into a single vector of 8-bit
+ * elements.  NB: The upper 8-bits of each 16-bit element must be zeros, else
+ * this will produce different results on different architectures.
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_pack_16(const Vector8 v1, const Vector8 v2)
+{
+#ifdef USE_SSE2
+	return _mm_packus_epi16(v1, v2);
+#elif defined(USE_NEON)
+	return vuzp1q_u8(v1, v2);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
+/*
+ * Unsigned shift left of each 32-bit element in the vector by 4 bits.
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_shift_left_nibble(const Vector8 v1)
+{
+#ifdef USE_SSE2
+	return _mm_slli_epi32(v1, 4);
+#elif defined(USE_NEON)
+	return (Vector8) vshlq_n_u32((Vector32) v1, 4);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
+/*
+ * Unsigned shift right of each 32-bit element in the vector by 4 bits.
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_shift_right_nibble(const Vector8 v1)
+{
+#ifdef USE_SSE2
+	return _mm_srli_epi32(v1, 4);
+#elif defined(USE_NEON)
+	return (Vector8) vshrq_n_u32((Vector32) v1, 4);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
+/*
+ * Unsigned shift right of each 32-bit element in the vector by 1 byte.
+ */
+#ifndef USE_NO_SIMD
+static inline Vector8
+vector8_shift_right_byte(const Vector8 v1)
+{
+#ifdef USE_SSE2
+	return _mm_srli_epi32(v1, 8);
+#elif defined(USE_NEON)
+	return (Vector8) vshrq_n_u32((Vector32) v1, 8);
+#endif
+}
+#endif							/* ! USE_NO_SIMD */
+
 #endif							/* SIMD_H */
diff --git a/src/test/regress/expected/strings.out b/src/test/regress/expected/strings.out
index 691e475bce3..3e351cf1cd0 100644
--- a/src/test/regress/expected/strings.out
+++ b/src/test/regress/expected/strings.out
@@ -260,6 +260,64 @@ SELECT reverse('\xabcd'::bytea);
  \xcdab
 (1 row)
 
+SELECT ('\x' || repeat(' ', 32))::bytea;
+ bytea 
+-------
+ \x
+(1 row)
+
+SELECT ('\x' || repeat('!', 33))::bytea;
+ERROR:  invalid hexadecimal digit: "!"
+SELECT ('\x' || repeat('/', 33))::bytea;
+ERROR:  invalid hexadecimal digit: "/"
+SELECT ('\x' || repeat('0', 32))::bytea;
+               bytea                
+------------------------------------
+ \x00000000000000000000000000000000
+(1 row)
+
+SELECT ('\x' || repeat('9', 32))::bytea;
+               bytea                
+------------------------------------
+ \x99999999999999999999999999999999
+(1 row)
+
+SELECT ('\x' || repeat(':', 33))::bytea;
+ERROR:  invalid hexadecimal digit: ":"
+SELECT ('\x' || repeat('@', 33))::bytea;
+ERROR:  invalid hexadecimal digit: "@"
+SELECT ('\x' || repeat('A', 32))::bytea;
+               bytea                
+------------------------------------
+ \xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+(1 row)
+
+SELECT ('\x' || repeat('F', 32))::bytea;
+               bytea                
+------------------------------------
+ \xffffffffffffffffffffffffffffffff
+(1 row)
+
+SELECT ('\x' || repeat('G', 33))::bytea;
+ERROR:  invalid hexadecimal digit: "G"
+SELECT ('\x' || repeat('`', 33))::bytea;
+ERROR:  invalid hexadecimal digit: "`"
+SELECT ('\x' || repeat('a', 32))::bytea;
+               bytea                
+------------------------------------
+ \xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+(1 row)
+
+SELECT ('\x' || repeat('f', 32))::bytea;
+               bytea                
+------------------------------------
+ \xffffffffffffffffffffffffffffffff
+(1 row)
+
+SELECT ('\x' || repeat('g', 33))::bytea;
+ERROR:  invalid hexadecimal digit: "g"
+SELECT ('\x' || repeat('~', 33))::bytea;
+ERROR:  invalid hexadecimal digit: "~"
 SET bytea_output TO escape;
 SELECT E'\\xDeAdBeEf'::bytea;
       bytea       
diff --git a/src/test/regress/sql/strings.sql b/src/test/regress/sql/strings.sql
index c05f3413699..35910369b6f 100644
--- a/src/test/regress/sql/strings.sql
+++ b/src/test/regress/sql/strings.sql
@@ -82,6 +82,22 @@ SELECT reverse(''::bytea);
 SELECT reverse('\xaa'::bytea);
 SELECT reverse('\xabcd'::bytea);
 
+SELECT ('\x' || repeat(' ', 32))::bytea;
+SELECT ('\x' || repeat('!', 33))::bytea;
+SELECT ('\x' || repeat('/', 33))::bytea;
+SELECT ('\x' || repeat('0', 32))::bytea;
+SELECT ('\x' || repeat('9', 32))::bytea;
+SELECT ('\x' || repeat(':', 33))::bytea;
+SELECT ('\x' || repeat('@', 33))::bytea;
+SELECT ('\x' || repeat('A', 32))::bytea;
+SELECT ('\x' || repeat('F', 32))::bytea;
+SELECT ('\x' || repeat('G', 33))::bytea;
+SELECT ('\x' || repeat('`', 33))::bytea;
+SELECT ('\x' || repeat('a', 32))::bytea;
+SELECT ('\x' || repeat('f', 32))::bytea;
+SELECT ('\x' || repeat('g', 33))::bytea;
+SELECT ('\x' || repeat('~', 33))::bytea;
+
 SET bytea_output TO escape;
 SELECT E'\\xDeAdBeEf'::bytea;
 SELECT E'\\x De Ad Be Ef '::bytea;
-- 
2.39.5 (Apple Git-154)


--9Pw58b1w01c2+m+5--