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Fix for BUG#41541 - Valgrind warnings on packed MyISAM table

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After the table is compressed by the myisampack utility,
opening the table by the server produces valgrind warnings.
      
This happens because when we try to read a record into the buffer
we alway assume that the remaining buffer to read is always equal 
to word size(4 or 8 or 2 bytes) we read. Sometimes we have 
remaining buffer size less than word size and trying to read the 
entire word size will end up in valgrind errors.
            
Fixed by reading byte by byte when we detect the remaining buffer 
size is less than the word size.
This commit is contained in:
Satya B 2009-03-25 14:45:53 +05:30
parent 8aff42f6a0
commit 7b1d72a096
3 changed files with 56 additions and 0 deletions
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26
myisam/mi_packrec.c
View file

@ -1430,6 +1430,32 @@ static void fill_buffer(MI_BIT_BUFF *bit_buff)
bit_buff->current_byte=0;
return;
}
else
{
uint len= 0;
uint i= 0;
/*
Check if the remaining buffer/record to read is less than the word size.
If so read byte by byte
Note: if this branch becomes a bottleneck it can be removed, assuming
that the second memory segment allocates 7 extra bytes (see
_mi_read_pack_info()).
*/
len= bit_buff->end - bit_buff->pos;
if (len < (BITS_SAVED / 8))
{
bit_buff->current_byte= 0;
for (i=0 ; i < len ; i++)
{
bit_buff->current_byte+= (((uint) ((uchar) bit_buff->pos[len - i - 1]))
<< (8 * i));
}
bit_buff->pos= bit_buff->end;
return;
}
}
#if BITS_SAVED == 64
bit_buff->current_byte= ((((uint) ((uchar) bit_buff->pos[7]))) +
(((uint) ((uchar) bit_buff->pos[6])) << 8) +

11
mysql-test/r/myisampack.result
View file

@ -27,3 +27,14 @@ CHECK TABLE t1 EXTENDED;
Table Op Msg_type Msg_text
test.t1 check status OK
DROP TABLE t1;
#
# BUG#41541 - Valgrind warnings on packed MyISAM table
#
CREATE TABLE t1(f1 VARCHAR(200), f2 TEXT);
INSERT INTO t1 VALUES ('foo', 'foo1'), ('bar', 'bar1');
FLUSH TABLE t1;
# Compress the table using MYISAMPACK tool
SELECT COUNT(*) FROM t1;
COUNT(*)
1024
DROP TABLE t1;

19
mysql-test/t/myisampack.test
View file

@ -31,3 +31,22 @@ FLUSH TABLES;
--exec $MYISAMCHK -s --unpack $MYSQLTEST_VARDIR/master-data/test/t1
CHECK TABLE t1 EXTENDED;
DROP TABLE t1;
--echo #
--echo # BUG#41541 - Valgrind warnings on packed MyISAM table
--echo #
CREATE TABLE t1(f1 VARCHAR(200), f2 TEXT);
INSERT INTO t1 VALUES ('foo', 'foo1'), ('bar', 'bar1');
let $i=9;
--disable_query_log
while ($i)
{
INSERT INTO t1 SELECT * FROM t1;
dec $i;
}
--enable_query_log
FLUSH TABLE t1;
--echo # Compress the table using MYISAMPACK tool
--exec $MYISAMPACK $MYSQLTEST_VARDIR/master-data/test/t1
SELECT COUNT(*) FROM t1;
DROP TABLE t1;