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Fix bitshiftright()'s zero-padding some more.

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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
This commit is contained in:
Tom Lane 2019-10-04 10:34:21 -04:00
parent e5ff975719
commit b8ddf0bdf7
3 changed files with 76 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
src/backend/utils/adt/varbit.c
View File

@ -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);
}

66
src/test/regress/expected/bit.out
View File

@ -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

6
src/test/regress/sql/bit.sql
View File

@ -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;