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MDEV-38752: Wrong result upon GROUP BY on a table with indexed virtual column after INSERT IGNORE #4759

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MDEV-38752: Wrong result upon GROUP BY on a table with indexed virtual column after INSERT IGNORE #4759

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MDEV-38752: Wrong result upon GROUP BY on a table with indexed virtua…
kjarir Mar 9, 2026
491f03f
Merge branch '12.3' into MDEV-38752-group-by-vcol-subst
kjarir Mar 11, 2026
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89 changes: 89 additions & 0 deletions mysql-test/main/mdev_38752.result
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#
# MDEV-38752: Wrong result upon GROUP BY on a table with indexed virtual column after INSERT IGNORE
#
# Case 1: Unsafe narrowing substitution (INT -> TINYINT)
CREATE TABLE t1 (a INT PRIMARY KEY, va TINYINT AS (a), KEY(va));
INSERT IGNORE INTO t1 (a) VALUES (100),(150),(200);
Warnings:
Warning 1264 Out of range value for column 'va' at row 2
Warning 1264 Out of range value for column 'va' at row 3
# Should return 3 rows (fix: substitution disallowed)
# EXPLAIN should show that va index is NOT used
EXPLAIN SELECT a, va, COUNT(*) FROM t1 GROUP BY a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 4 NULL # Using index
Warnings:
Note 1105 Cannot substitute virtual column expression `t1`.`a` -> va due to type mismatch
SHOW WARNINGS;
Level Code Message
Note 1105 Cannot substitute virtual column expression `t1`.`a` -> va due to type mismatch
SELECT a, va, COUNT(*) FROM t1 GROUP BY a;
a va COUNT(*)
100 100 1
150 127 1
200 127 1
DROP TABLE t1;
# Case 2: Safe substitution (INT -> INT)
CREATE TABLE t2 (a INT PRIMARY KEY, va INT AS (a), KEY(va));
INSERT INTO t2 (a) VALUES (100),(150),(200);
# Should return 3 rows (substitution allowed, uses va index)
# EXPLAIN should show that va index is used
EXPLAIN SELECT va, COUNT(*) FROM t2 GROUP BY a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index NULL va 5 NULL # Using index
SHOW WARNINGS;
Level Code Message
SELECT va, COUNT(*) FROM t2 GROUP BY a;
va COUNT(*)
100 1
150 1
200 1
DROP TABLE t2;
# Case 3: Unsafe narrowing for VARCHAR
CREATE TABLE t3 (a VARCHAR(20) PRIMARY KEY, va VARCHAR(5) AS (a), KEY(va));
INSERT IGNORE INTO t3 (a) VALUES ('apple'),('banana'),('apricot');
Warnings:
Warning 1265 Data truncated for column 'va' at row 2
Warning 1265 Data truncated for column 'va' at row 3
# 'apple' and 'apricot' both truncate to 'apple' in va
# Should return 3 rows
# EXPLAIN should show that va index is NOT used
EXPLAIN SELECT a, va, COUNT(*) FROM t3 GROUP BY a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index NULL PRIMARY 82 NULL # Using index
Warnings:
Note 1105 Cannot substitute virtual column expression `t3`.`a` -> va due to type mismatch
SHOW WARNINGS;
Level Code Message
Note 1105 Cannot substitute virtual column expression `t3`.`a` -> va due to type mismatch
SELECT a, va, COUNT(*) FROM t3 GROUP BY a;
a va COUNT(*)
apple apple 1
apricot apric 1
banana banan 1
DROP TABLE t3;
# Case 4: Unsafe narrowing for DECIMAL
CREATE TABLE t4 (a DECIMAL(10,5) PRIMARY KEY, va DECIMAL(10,2) AS (a), KEY(va));
INSERT IGNORE INTO t4 (a) VALUES (1.12345), (1.12346), (1.12999);
Warnings:
Note 1265 Data truncated for column 'va' at row 1
Note 1265 Data truncated for column 'va' at row 2
Note 1265 Data truncated for column 'va' at row 3
# All three values truncate to 1.12 in va
# Should return 3 rows
# EXPLAIN should show that va index is NOT used
EXPLAIN SELECT a, va, COUNT(*) FROM t4 GROUP BY a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t4 index NULL PRIMARY 6 NULL # Using index
Warnings:
Note 1105 Cannot substitute virtual column expression `t4`.`a` -> va due to type mismatch
SHOW WARNINGS;
Level Code Message
Note 1105 Cannot substitute virtual column expression `t4`.`a` -> va due to type mismatch
SELECT a, va, COUNT(*) FROM t4 GROUP BY a;
a va COUNT(*)
1.12345 1.12 1
1.12346 1.12 1
1.12999 1.13 1
DROP TABLE t4;
# End of mdev_38752 tests
53 changes: 53 additions & 0 deletions mysql-test/main/mdev_38752.test
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--source include/have_innodb.inc

--echo #
--echo # MDEV-38752: Wrong result upon GROUP BY on a table with indexed virtual column after INSERT IGNORE
--echo #

--echo # Case 1: Unsafe narrowing substitution (INT -> TINYINT)
CREATE TABLE t1 (a INT PRIMARY KEY, va TINYINT AS (a), KEY(va));
INSERT IGNORE INTO t1 (a) VALUES (100),(150),(200);
--echo # Should return 3 rows (fix: substitution disallowed)
--echo # EXPLAIN should show that va index is NOT used
--replace_column 9 #
EXPLAIN SELECT a, va, COUNT(*) FROM t1 GROUP BY a;
SHOW WARNINGS;
SELECT a, va, COUNT(*) FROM t1 GROUP BY a;
DROP TABLE t1;

--echo # Case 2: Safe substitution (INT -> INT)
CREATE TABLE t2 (a INT PRIMARY KEY, va INT AS (a), KEY(va));
INSERT INTO t2 (a) VALUES (100),(150),(200);
--echo # Should return 3 rows (substitution allowed, uses va index)
--echo # EXPLAIN should show that va index is used
--replace_column 9 #
EXPLAIN SELECT va, COUNT(*) FROM t2 GROUP BY a;
SHOW WARNINGS;
SELECT va, COUNT(*) FROM t2 GROUP BY a;
DROP TABLE t2;

--echo # Case 3: Unsafe narrowing for VARCHAR
CREATE TABLE t3 (a VARCHAR(20) PRIMARY KEY, va VARCHAR(5) AS (a), KEY(va));
INSERT IGNORE INTO t3 (a) VALUES ('apple'),('banana'),('apricot');
--echo # 'apple' and 'apricot' both truncate to 'apple' in va
--echo # Should return 3 rows
--echo # EXPLAIN should show that va index is NOT used
--replace_column 9 #
EXPLAIN SELECT a, va, COUNT(*) FROM t3 GROUP BY a;
SHOW WARNINGS;
SELECT a, va, COUNT(*) FROM t3 GROUP BY a;
DROP TABLE t3;
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@gkodinov gkodinov Mar 9, 2026

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we customarily end tests with a print like that:

--echo End of ... tests.

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@gkodinov gkodinov Mar 9, 2026

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Please also make sure all of the related failing tests are re-recorded.

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@grooverdan grooverdan Mar 11, 2026

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@kjarir note this is --echo End of 12.3 tests rather the test name.


--echo # Case 4: Unsafe narrowing for DECIMAL
CREATE TABLE t4 (a DECIMAL(10,5) PRIMARY KEY, va DECIMAL(10,2) AS (a), KEY(va));
INSERT IGNORE INTO t4 (a) VALUES (1.12345), (1.12346), (1.12999);
--echo # All three values truncate to 1.12 in va
--echo # Should return 3 rows
--echo # EXPLAIN should show that va index is NOT used
--replace_column 9 #
EXPLAIN SELECT a, va, COUNT(*) FROM t4 GROUP BY a;
SHOW WARNINGS;
SELECT a, va, COUNT(*) FROM t4 GROUP BY a;
DROP TABLE t4;

--echo # End of mdev_38752 tests
86 changes: 67 additions & 19 deletions mysql-test/suite/vcol/r/order_by_group_by_subst.result
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Expand Up @@ -18,12 +18,16 @@ id select_type table type possible_keys key key_len ref rows Extra
explain select c + 1 from t order by c + 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select c + 1 from t order by vc;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using filesort
explain select vc from t order by c + 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 10000 Using index
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select vc from t order by c;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 10000 Using index
Expand All @@ -33,28 +37,40 @@ id select_type table type possible_keys key key_len ref rows Extra
explain select c from t order by c + 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select vc from t order by c + 1 limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 2 Using index
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select c + 1 from t order by c + 1 limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 2
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select c + 1 from t order by vc limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 2
explain delete from t order by c + 1 limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 2
1 SIMPLE t ALL NULL NULL NULL NULL 10000 Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
alter table t add column d int;
explain update t set d = 500 order by c + 1 limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 2 Using buffer
1 SIMPLE t ALL NULL NULL NULL NULL 10000 Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain update t set d = 500 order by c limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 2 Using buffer
explain update t set c = 500 order by c + 1 limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 2 Using buffer
1 SIMPLE t ALL NULL NULL NULL NULL 10000 Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain update t set c = 500 order by c limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 2 Using buffer
Expand All @@ -66,10 +82,14 @@ add column vc int as (c + 1),
add index(vc);
explain select vc from t order by c + 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 10000 Using index
1 SIMPLE t ALL NULL NULL NULL NULL 10000 Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select vc from t order by c + 1 limit 10;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 10 Using index
1 SIMPLE t ALL NULL NULL NULL NULL 10000 Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
drop table t;
create table t (c int, key (c));
insert into t select seq from seq_1_to_10000;
Expand All @@ -84,10 +104,14 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using filesort
explain select vc2 from t order by vc1 * 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc2 5 NULL 10000 Using index
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`vc1` * 2 -> vc2 due to type mismatch
explain select vc2 from t order by vc1 * 2 limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc2 5 NULL 2 Using index
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`vc1` * 2 -> vc2 due to type mismatch
drop table t;
create table t (c int, vc int generated always as (1 + 1) virtual, key (c));
insert into t values (42, default), (83, default);
Expand All @@ -108,7 +132,10 @@ add column vc2 int as (1 - c),
add index(vc1, vc2);
explain select vc1, vc2 from t order by c + 1, 1 - c;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc1 10 NULL 10000 Using index
1 SIMPLE t ALL NULL NULL NULL NULL 10000 Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc1 due to type mismatch
Note 1105 Cannot substitute virtual column expression 1 - `t`.`c` -> vc2 due to type mismatch
drop table t;
create table t (c int, key (c));
insert into t select seq from seq_1_to_10000;
Expand All @@ -127,12 +154,16 @@ id select_type table type possible_keys key key_len ref rows Extra
explain select c + 1 from t group by c + 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using temporary; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select c + 1 from t group by vc;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using temporary; Using filesort
explain select vc from t group by c + 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 10000 Using index
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using temporary; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select vc from t group by c;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 10000 Using index
Expand All @@ -142,12 +173,18 @@ id select_type table type possible_keys key key_len ref rows Extra
explain select c from t group by c + 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using temporary; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select vc from t group by c + 1 limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 2 Using index
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using temporary; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select c + 1 from t group by c + 1 limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 2
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using temporary; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select c + 1 from t group by vc limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 2
Expand All @@ -159,10 +196,14 @@ add column vc int as (c + 1),
add index(vc);
explain select vc from t group by c + 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 10000 Using index
1 SIMPLE t ALL NULL NULL NULL NULL 10000 Using temporary; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
explain select vc from t group by c + 1 limit 10;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc 5 NULL 10 Using index
1 SIMPLE t ALL NULL NULL NULL NULL 10000 Using temporary; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc due to type mismatch
drop table t;
create table t (c int, key (c));
insert into t select seq from seq_1_to_10000;
Expand All @@ -177,10 +218,14 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using temporary; Using filesort
explain select vc2 from t group by vc1 * 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc2 5 NULL 10000 Using index
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using temporary; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`vc1` * 2 -> vc2 due to type mismatch
explain select vc2 from t group by vc1 * 2 limit 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc2 5 NULL 2 Using index
1 SIMPLE t index NULL c 5 NULL 10000 Using index; Using temporary; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`vc1` * 2 -> vc2 due to type mismatch
drop table t;
create table t (c int);
insert into t select seq from seq_1_to_10000;
Expand All @@ -191,7 +236,10 @@ add column vc2 int as (1 - c),
add index(vc1, vc2);
explain select vc1, vc2 from t group by c + 1, 1 - c;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t index NULL vc1 10 NULL 10000 Using index
1 SIMPLE t ALL NULL NULL NULL NULL 10000 Using temporary; Using filesort
Warnings:
Note 1105 Cannot substitute virtual column expression `t`.`c` + 1 -> vc1 due to type mismatch
Note 1105 Cannot substitute virtual column expression 1 - `t`.`c` -> vc2 due to type mismatch
drop table t;
#
# MDEV-37435 Assertion `field' failed in virtual bool Item_field::fix_fields(THD *, Item **)
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