From 30e5b3bbe9ca9f3594816788fe4469798da04f64 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 4 Oct 2019 10:34:21 -0400
Subject: [PATCH] Fix bitshiftright()'s zero-padding some more.
Commit 5ac0d9360 failed to entirely fix bitshiftright's habit of
leaving one-bits in the pad space that should be all zeroes,
because in a moment of sheer brain fade I'd concluded that only
the code path used for not-a-multiple-of-8 shift distances needed
to be fixed. Of course, a multiple-of-8 shift distance can also
cause the problem, so we need to forcibly zero the extra bits
in both cases.
Per bug #16037 from Alexander Lakhin. As before, back-patch to all
supported branches.
Discussion: https://postgr.es/m/16037-1d1ebca564db54f4@postgresql.org
---
src/backend/utils/adt/varbit.c | 6 ++-
src/test/regress/expected/bit.out | 66 +++++++++++++++++++++++++++++++
src/test/regress/sql/bit.sql | 6 +++
3 files changed, 76 insertions(+), 2 deletions(-)
diff --git a/src/backend/utils/adt/varbit.c b/src/backend/utils/adt/varbit.c
index 3b409d7d3b..ef57fdac78 100644
--- a/src/backend/utils/adt/varbit.c
+++ b/src/backend/utils/adt/varbit.c
@@ -1473,6 +1473,7 @@ bitshiftright(PG_FUNCTION_ARGS)
/* Special case: we can do a memcpy */
len = VARBITBYTES(arg) - byte_shift;
memcpy(r, p, len);
+ r += len;
}
else
{
@@ -1484,10 +1485,11 @@ bitshiftright(PG_FUNCTION_ARGS)
if ((++r) < VARBITEND(result))
*r = (*p << (BITS_PER_BYTE - ishift)) & BITMASK;
}
- /* We may have shifted 1's into the pad bits, so fix that */
- VARBIT_PAD_LAST(result, r);
}
+ /* We may have shifted 1's into the pad bits, so fix that */
+ VARBIT_PAD_LAST(result, r);
+
PG_RETURN_VARBIT_P(result);
}
diff --git a/src/test/regress/expected/bit.out b/src/test/regress/expected/bit.out
index 07491bb84c..657b91a89f 100644
--- a/src/test/regress/expected/bit.out
+++ b/src/test/regress/expected/bit.out
@@ -499,6 +499,28 @@ SELECT b, b >> 1 AS bsr, b << 1 AS bsl
0000000000000001 | 0000000000000000 | 0000000000000010
(16 rows)
+SELECT b, b >> 8 AS bsr8, b << 8 AS bsl8
+ FROM BIT_SHIFT_TABLE ;
+ b | bsr8 | bsl8
+------------------+------------------+------------------
+ 1101100000000000 | 0000000011011000 | 0000000000000000
+ 0110110000000000 | 0000000001101100 | 0000000000000000
+ 0011011000000000 | 0000000000110110 | 0000000000000000
+ 0001101100000000 | 0000000000011011 | 0000000000000000
+ 0000110110000000 | 0000000000001101 | 1000000000000000
+ 0000011011000000 | 0000000000000110 | 1100000000000000
+ 0000001101100000 | 0000000000000011 | 0110000000000000
+ 0000000110110000 | 0000000000000001 | 1011000000000000
+ 0000000011011000 | 0000000000000000 | 1101100000000000
+ 0000000001101100 | 0000000000000000 | 0110110000000000
+ 0000000000110110 | 0000000000000000 | 0011011000000000
+ 0000000000011011 | 0000000000000000 | 0001101100000000
+ 0000000000001101 | 0000000000000000 | 0000110100000000
+ 0000000000000110 | 0000000000000000 | 0000011000000000
+ 0000000000000011 | 0000000000000000 | 0000001100000000
+ 0000000000000001 | 0000000000000000 | 0000000100000000
+(16 rows)
+
SELECT b::bit(15), b::bit(15) >> 1 AS bsr, b::bit(15) << 1 AS bsl
FROM BIT_SHIFT_TABLE ;
b | bsr | bsl
@@ -521,6 +543,28 @@ SELECT b::bit(15), b::bit(15) >> 1 AS bsr, b::bit(15) << 1 AS bsl
000000000000000 | 000000000000000 | 000000000000000
(16 rows)
+SELECT b::bit(15), b::bit(15) >> 8 AS bsr8, b::bit(15) << 8 AS bsl8
+ FROM BIT_SHIFT_TABLE ;
+ b | bsr8 | bsl8
+-----------------+-----------------+-----------------
+ 110110000000000 | 000000001101100 | 000000000000000
+ 011011000000000 | 000000000110110 | 000000000000000
+ 001101100000000 | 000000000011011 | 000000000000000
+ 000110110000000 | 000000000001101 | 000000000000000
+ 000011011000000 | 000000000000110 | 100000000000000
+ 000001101100000 | 000000000000011 | 110000000000000
+ 000000110110000 | 000000000000001 | 011000000000000
+ 000000011011000 | 000000000000000 | 101100000000000
+ 000000001101100 | 000000000000000 | 110110000000000
+ 000000000110110 | 000000000000000 | 011011000000000
+ 000000000011011 | 000000000000000 | 001101100000000
+ 000000000001101 | 000000000000000 | 000110100000000
+ 000000000000110 | 000000000000000 | 000011000000000
+ 000000000000011 | 000000000000000 | 000001100000000
+ 000000000000001 | 000000000000000 | 000000100000000
+ 000000000000000 | 000000000000000 | 000000000000000
+(16 rows)
+
CREATE TABLE VARBIT_SHIFT_TABLE(v BIT VARYING(20));
INSERT INTO VARBIT_SHIFT_TABLE VALUES (B'11011');
INSERT INTO VARBIT_SHIFT_TABLE SELECT CAST(v || B'0' AS BIT VARYING(6)) >>1 FROM VARBIT_SHIFT_TABLE;
@@ -573,6 +617,28 @@ SELECT v, v >> 1 AS vsr, v << 1 AS vsl
00000000000000011011 | 00000000000000001101 | 00000000000000110110
(16 rows)
+SELECT v, v >> 8 AS vsr8, v << 8 AS vsl8
+ FROM VARBIT_SHIFT_TABLE ;
+ v | vsr8 | vsl8
+----------------------+----------------------+----------------------
+ 11011 | 00000 | 00000
+ 011011 | 000000 | 000000
+ 0011011 | 0000000 | 0000000
+ 00011011 | 00000000 | 00000000
+ 000011011 | 000000000 | 100000000
+ 0000011011 | 0000000000 | 1100000000
+ 00000011011 | 00000000000 | 01100000000
+ 000000011011 | 000000000000 | 101100000000
+ 0000000011011 | 0000000000000 | 1101100000000
+ 00000000011011 | 00000000000000 | 01101100000000
+ 000000000011011 | 000000000000000 | 001101100000000
+ 0000000000011011 | 0000000000000000 | 0001101100000000
+ 00000000000011011 | 00000000000000000 | 00001101100000000
+ 000000000000011011 | 000000000000000000 | 000001101100000000
+ 0000000000000011011 | 0000000000000000000 | 0000001101100000000
+ 00000000000000011011 | 00000000000000000000 | 00000001101100000000
+(16 rows)
+
DROP TABLE BIT_SHIFT_TABLE;
DROP TABLE VARBIT_SHIFT_TABLE;
-- Get/Set bit
diff --git a/src/test/regress/sql/bit.sql b/src/test/regress/sql/bit.sql
index cf2460b212..a740c28e2d 100644
--- a/src/test/regress/sql/bit.sql
+++ b/src/test/regress/sql/bit.sql
@@ -170,8 +170,12 @@ SELECT POSITION(B'1101' IN b),
FROM BIT_SHIFT_TABLE ;
SELECT b, b >> 1 AS bsr, b << 1 AS bsl
FROM BIT_SHIFT_TABLE ;
+SELECT b, b >> 8 AS bsr8, b << 8 AS bsl8
+ FROM BIT_SHIFT_TABLE ;
SELECT b::bit(15), b::bit(15) >> 1 AS bsr, b::bit(15) << 1 AS bsl
FROM BIT_SHIFT_TABLE ;
+SELECT b::bit(15), b::bit(15) >> 8 AS bsr8, b::bit(15) << 8 AS bsl8
+ FROM BIT_SHIFT_TABLE ;
CREATE TABLE VARBIT_SHIFT_TABLE(v BIT VARYING(20));
@@ -186,6 +190,8 @@ SELECT POSITION(B'1101' IN v),
FROM VARBIT_SHIFT_TABLE ;
SELECT v, v >> 1 AS vsr, v << 1 AS vsl
FROM VARBIT_SHIFT_TABLE ;
+SELECT v, v >> 8 AS vsr8, v << 8 AS vsl8
+ FROM VARBIT_SHIFT_TABLE ;
DROP TABLE BIT_SHIFT_TABLE;
DROP TABLE VARBIT_SHIFT_TABLE;
--
2.40.0