[MDEV-18922] Alter on long unique varchar column makes result null Created: 2019-03-14  Updated: 2019-03-22  Resolved: 2019-03-17

Status: Closed
Project: MariaDB Server
Component/s: Server
Affects Version/s: 10.4.3
Fix Version/s: 10.4.4

Type: Bug Priority: Blocker
Reporter: Sachin Setiya (Inactive) Assignee: Sachin Setiya (Inactive)
Resolution: Fixed Votes: 0
Labels: None
Environment:

All

Issue Links:
PartOf
is part of MDEV-18901 Wrong results after ADD UNIQUE INDEX(... Closed
Problem/Incident
causes MDEV-18941 HEAP index is no longer used Closed
is caused by MDEV-371 Unique indexes for blobs Closed

 Description    

 
 
#
 
#MDEV-18922 Alter on long unique varchar column makes result null
 
#
 
CREATE TABLE t1 (b int, a  varchar(4000));
 
INSERT INTO t1 VALUES (1, 2),(2,3),(3,4);
 
ALTER TABLE t1 ADD UNIQUE INDEX (a);
 
SELECT * FROM t1;
 
SELECT a FROM t1;
 
drop table t1;
 
 

Result

CREATE TABLE t1 (b int, a  varchar(4000));
 
INSERT INTO t1 VALUES (1, 2),(2,3),(3,4);
 
ALTER TABLE t1 ADD UNIQUE INDEX (a);
 
SELECT * FROM t1;
 
b       a
 
1       2
 
2       3
 
3       4
 
SELECT a FROM t1;
 
a
 
NULL
 
NULL
 
NULL
 
drop table t1;



 Comments   
Comment by Sachin Setiya (Inactive) [ 2019-03-14 ]

Even this is giving NULL

# with VARCHAR(79) or blob  all results are correct
 
CREATE TABLE t1 (a int);
 
 
 
INSERT INTO t1 VALUES (1),(2);
 
 
 
ALTER TABLE t1 ADD UNIQUE (a) using hash;
 
# returns 2 rows with a=NULL, instead of rows 1,2
 
SELECT * FROM t1;
 
drop table t1;

While this is not giving NULL which is strange

# with VARCHAR(79) or blob  all results are correct
 
CREATE TABLE t1 (a blob);
 
 
 
INSERT INTO t1 VALUES (1),(2);
 
 
 
ALTER TABLE t1 ADD UNIQUE (a) using hash;
 
# returns 2 rows with a=NULL, instead of rows 1,2
 
SELECT * FROM t1;
 
drop table t1;

So the field which stores the result in table->record itself is affected , while the fields which store the data pointer is not affected.

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