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MDEV-15762 - VARCHAR(0) COMPRESSED crashes the server

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Character set safe truncation is done when storing non-empty string in
VARCHAR(0) COMPRESSED column, so that string becomes empty. The code
didn't expect empty string after truncation.

Fixed by moving empty string check after truncation.
This commit is contained in:
Sergey Vojtovich
2018-04-03 16:19:37 +04:00
parent 43ab88f0ea
commit 3dec6c48bc
3 changed files with 27 additions and 8 deletions
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13
mysql-test/main/column_compression.result
View File

@ -1373,3 +1373,16 @@ bar
foo
SET SESSION optimizer_switch=DEFAULT;
DROP TABLE t1;
#
# MDEV-15762 - VARCHAR(0) COMPRESSED crashes the server
#
CREATE TABLE t1(a VARCHAR(0) COMPRESSED);
INSERT INTO t1 VALUES('a');
ERROR 22001: Data too long for column 'a' at row 1
INSERT INTO t1 VALUES(' ');
Warnings:
Note 1265 Data truncated for column 'a' at row 1
SELECT LENGTH(a) FROM t1;
LENGTH(a)
0
DROP TABLE t1;

11
mysql-test/main/column_compression.test
View File

@ -91,3 +91,14 @@ SET SESSION optimizer_switch = 'derived_merge=off';
SELECT * FROM ( SELECT * FROM t1 ) AS sq ORDER BY b;
SET SESSION optimizer_switch=DEFAULT;
DROP TABLE t1;
--echo #
--echo # MDEV-15762 - VARCHAR(0) COMPRESSED crashes the server
--echo #
CREATE TABLE t1(a VARCHAR(0) COMPRESSED);
--error ER_DATA_TOO_LONG
INSERT INTO t1 VALUES('a');
INSERT INTO t1 VALUES(' ');
SELECT LENGTH(a) FROM t1;
DROP TABLE t1;

11
sql/field.cc
View File

@ -7958,12 +7958,6 @@ int Field_longstr::compress(char *to, uint *to_length,
char *buf= 0;
int rc= 0;
if (length == 0)
{
*to_length= 0;
return 0;
}
if (String::needs_conversion_on_storage(length, cs, field_charset) ||
*to_length <= length)
{
@ -7981,10 +7975,11 @@ int Field_longstr::compress(char *to, uint *to_length,
(*to_length - 1) / field_charset->mbmaxlen);
rc= check_conversion_status(&copier, end, cs, true);
from= buf;
DBUG_ASSERT(length > 0);
}
if (length >= thd->variables.column_compression_threshold &&
if (length == 0)
*to_length= 0;
else if (length >= thd->variables.column_compression_threshold &&
(*to_length= compression_method()->compress(thd, to, from, length)))
status_var_increment(thd->status_var.column_compressions);
else