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Bug#15757: Wrong SUBSTRING() result when a tmp table was employed.

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When the SUBSTRING() function was used over a LONGTEXT field the max_length of
the SUBSTRING() result was wrongly calculated and set to 0. As the max_length
parameter is used while tmp field creation it limits the length of the result
field and leads to printing an empty string instead of the correct result.

Now the Item_func_substr::fix_length_and_dec() function correctly calculates
the max_length parameter.
This commit is contained in:
evgen@moonbone.local
2007-03-10 19:55:34 +03:00
parent 999c1cdcc1
commit 6f6b9ae3ad
3 changed files with 25 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
mysql-test/r/func_str.result
View File

@ -1946,4 +1946,15 @@ NULL
SELECT UNHEX('G') IS NULL; SELECT UNHEX('G') IS NULL;
UNHEX('G') IS NULL UNHEX('G') IS NULL
1 1
create table t1(f1 longtext);
insert into t1 values ("123"),("456");
select substring(f1,1,1) from t1 group by 1;
substring(f1,1,1)
1
4
create table t2(f1 varchar(3));
insert into t1 values ("123"),("456");
select substring(f1,4,1), substring(f1,-4,1) from t2;
substring(f1,4,1) substring(f1,-4,1)
drop table t1,t2;
End of 5.0 tests End of 5.0 tests

11
mysql-test/t/func_str.test
View File

@ -1014,4 +1014,15 @@ select lpad('abc', cast(5 as unsigned integer), 'x');
SELECT UNHEX('G'); SELECT UNHEX('G');
SELECT UNHEX('G') IS NULL; SELECT UNHEX('G') IS NULL;
#
# Bug#15757: Wrong SUBSTRING() result when a tmp table was employed.
#
create table t1(f1 longtext);
insert into t1 values ("123"),("456");
select substring(f1,1,1) from t1 group by 1;
create table t2(f1 varchar(3));
insert into t1 values ("123"),("456");
select substring(f1,4,1), substring(f1,-4,1) from t2;
drop table t1,t2;
--echo End of 5.0 tests --echo End of 5.0 tests

7
sql/item_strfunc.cc
View File

@ -1184,11 +1184,10 @@ void Item_func_substr::fix_length_and_dec()
if (args[1]->const_item()) if (args[1]->const_item())
{ {
int32 start= (int32) args[1]->val_int(); int32 start= (int32) args[1]->val_int();
start= (int32)((start < 0) ? max_length + start : start - 1); if (start < 0)
if (start < 0 || start >= (int32) max_length) max_length= ((uint)(-start) > max_length) ? 0 : (uint)(-start);
max_length=0; /* purecov: inspected */
else else
max_length-= (uint) start; max_length-= min((uint)(start - 1), max_length);
} }
if (arg_count == 3 && args[2]->const_item()) if (arg_count == 3 && args[2]->const_item())
{ {