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From: Zsolt Parragi <zsolt.parragi@percona.com>
Date: Tue, 24 Feb 2026 18:33:19 +0000
Message-ID: <CAN4CZFOqX_Mdjvw66tKrKAuv5zpwiz_EiGjH=JvBBDq-a+G+YQ@mail.gmail.com>
Subject: Re: More speedups for tuple deformation
To: David Rowley <dgrowleyml@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, John Naylor <johncnaylorls@gmail.com>, 
	Chao Li <li.evan.chao@gmail.com>, 
	PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
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Archived-At: <https://www.postgresql.org/message-id/CAN4CZFOqX_Mdjvw66tKrKAuv5zpwiz_EiGjH%3DJvBBDq-a%2BG%2BYQ%40mail.gmail.com>
Precedence: bulk

Hello

+ * We expect that 'bits' contains at least one 0 bit somewhere in the mask,
+ * not necessarily < natts.
+ */

Is this precondition really enough?

Let's say we have 20 attributes, only attribute 20 is NULL
Caller requests natts=8

That sets lastByte = 1, loop only checks bits[0], which is 0xFF, exits
with bytenum=1, bits[1] is also 0xFF

Then we execute

+ res += pg_rightmost_one_pos32(~bits[bytenum]);

where ~0xFF = 0


+ /* convert the lower 4 bits of null bitmap word into 32 bit int */
+ isnull_8 = (nullbyte & 0xf) * SPREAD_BITS_MULTIPLIER_32;
+
+ /*
+ * convert the upper 4 bits of null bitmap word into 32 bit int, shift
+ * into the upper 32 bit
+ */
+ isnull_8 |= ((uint64) ((nullbyte >> 4) * SPREAD_BITS_MULTIPLIER_32)) << 32;
+
+ /* mask out all other bits apart from the lowest bit of each byte */
+ isnull_8 &= UINT64CONST(0x0101010101010101);
+ memcpy(isnull, &isnull_8, sizeof(uint64));


Won't this mix up column numbers on big-endian systems?


Subject: [PATCH v9 1/5] Introduce deform_bench test module

For benchmaring tuple deformation.
---

Typo: should be benchmarking


+ * firstNonGuaranteedAttr stores the index to info the compact_attrs array for

to info should be "into"?