Mixing
An UPDATE runs unexpectedly on MySQL 5.7 whereas it runs as expected on prior versions
Clash Royale CLAN TAG#URR8PPP
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty margin-bottom:0;
up vote
3
down vote
favorite
I use a column called sequence on tables where I have to re-sort blocks of rows into an arbitrarily order.
CREATE TABLE `tkmemberstage` (
`ID` bigint(22) unsigned NOT NULL AUTO_INCREMENT,
`tkmembershipID` bigint(22) unsigned NOT NULL DEFAULT '0',
`sequence` int(11) NOT NULL DEFAULT '0',
PRIMARY KEY (`ID`),
KEY `tkmembershipID` (`tkmembershipID`)
)
insert into tkmemberstage set tkmembershipID = 1, sequence = 10;
insert into tkmemberstage set tkmembershipID = 1, sequence = 20;
insert into tkmemberstage set tkmembershipID = 1, sequence = 30;
insert into tkmemberstage set tkmembershipID = 1, sequence = 40;
A few years back I researched the following as a means of resequencing a block of rows in a single UPDATE
This works by creating an interim virtual table and then updating the entire block of rows in one transaction instead of having to write each row out programmatically.
The UPDATE statement goes like this:
update
tkmemberstage
join
(select tkmemberstage.ID,
(@newSequence := @newSequence+10) as newSequence
from
tkmemberstage
cross join
(select @newSequence := 0)
constructedTable
where
tkmemberstage.tkmembershipID = 1
order by tkmemberstage.sequence)
constructedTableReordered
on tkmemberstage.ID=constructedTableReordered.ID
set tkmemberstage.sequence=constructedTableReordered.newSequence;
I have copied it verbatim from a development server in order not to add any translation problems to the mix.
I currently have this running on a mix of RDS servers in the AWS cloud and on anything other than a 5.7 server it works as expected.
In troubleshooting this I tried to deconstruct the statement and try it in partial chunks.
Here is the dataset I'm working on:
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
+----+----------+
4 rows in set (0.00 sec)
I then perform an update to sequence on a single row:
mysql> update tkmemberstage set sequence=sequence - 11 where tkmemberstage.ID = 4;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 29 |
+----+----------+
4 rows in set (0.00 sec)
Now if I run the SELECT part of the UPDATE statement I get exactly what we expect:
mysql> select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence;
+----+-------------+
| ID | newSequence |
+----+-------------+
| 1 | 10 |
| 2 | 20 |
| 4 | 30 |
| 3 | 40 |
+----+-------------+
4 rows in set (0.01 sec)
And yet when I run the final UPDATE statement itself here is the result:
mysql> update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
Query OK, 1 row affected (0.00 sec)
Rows matched: 4 Changed: 1 Warnings: 0
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
+----+----------+
4 rows in set (0.00 sec)
So the first obvious question is what changed in 5.7 that could/would cause this kind of behaviour.
(It's been consistent for well over 6 months now. I just patched the 5.7 server today and retested and still the same results. I also installed 5.7 on a AWS AMI (Cloud9) instance where I did these tests so this behaviour is now confirmed on numerous instances of 5.7.)
The second question is of course what exactly do we do about it?
The third, a nice to know, is how would we go deeper in troubleshooting this?
For what it is worth here is the EXPLAIN of the UPDATE on 5.7:
mysql> explain update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
| 1 | UPDATE | tkmemberstage | NULL | ALL | PRIMARY | NULL | NULL | NULL | 4 | 100.00 | NULL |
| 1 | PRIMARY | <derived2> | NULL | ref | <auto_key0> | <auto_key0> | 8 | well20180515.tkmemberstage.ID | 2 | 100.00 | NULL |
| 2 | DERIVED | tkmemberstage | NULL | ALL | tkmembershipID | NULL | NULL | NULL | 4 | 100.00 | Using where; Using temporary; Using filesort |
| 2 | DERIVED | <derived3> | NULL | ALL | NULL | NULL | NULL | NULL | 1 | 100.00 | Using join buffer (Block Nested Loop) |
| 3 | DERIVED | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used |
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
5 rows in set (0.00 sec)
Whereas here is the EXPLAIN on a non 5.7 version:
mysql> explain update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
| 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 2 | NULL |
| 1 | PRIMARY | tkmemberstage | eq_ref | PRIMARY | PRIMARY | 8 | constructedTableReordered.ID | 1 | NULL |
| 2 | DERIVED | <derived3> | system | NULL | NULL | NULL | NULL | 1 | Using filesort |
| 2 | DERIVED | tkmemberstage | ref | tkmembershipID | tkmembershipID | 8 | const | 1 | Using where |
| 3 | DERIVED | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used |
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
5 rows in set (0.03 sec)
mysql update query
asked 5 hours ago
Techmag
1185
New contributor
Techmag is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
 |Â
show 1 more comment
up vote
3
down vote
favorite
I use a column called sequence on tables where I have to re-sort blocks of rows into an arbitrarily order.
CREATE TABLE `tkmemberstage` (
`ID` bigint(22) unsigned NOT NULL AUTO_INCREMENT,
`tkmembershipID` bigint(22) unsigned NOT NULL DEFAULT '0',
`sequence` int(11) NOT NULL DEFAULT '0',
PRIMARY KEY (`ID`),
KEY `tkmembershipID` (`tkmembershipID`)
)
insert into tkmemberstage set tkmembershipID = 1, sequence = 10;
insert into tkmemberstage set tkmembershipID = 1, sequence = 20;
insert into tkmemberstage set tkmembershipID = 1, sequence = 30;
insert into tkmemberstage set tkmembershipID = 1, sequence = 40;
A few years back I researched the following as a means of resequencing a block of rows in a single UPDATE
This works by creating an interim virtual table and then updating the entire block of rows in one transaction instead of having to write each row out programmatically.
The UPDATE statement goes like this:
update
tkmemberstage
join
(select tkmemberstage.ID,
(@newSequence := @newSequence+10) as newSequence
from
tkmemberstage
cross join
(select @newSequence := 0)
constructedTable
where
tkmemberstage.tkmembershipID = 1
order by tkmemberstage.sequence)
constructedTableReordered
on tkmemberstage.ID=constructedTableReordered.ID
set tkmemberstage.sequence=constructedTableReordered.newSequence;
I have copied it verbatim from a development server in order not to add any translation problems to the mix.
I currently have this running on a mix of RDS servers in the AWS cloud and on anything other than a 5.7 server it works as expected.
In troubleshooting this I tried to deconstruct the statement and try it in partial chunks.
Here is the dataset I'm working on:
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
+----+----------+
4 rows in set (0.00 sec)
I then perform an update to sequence on a single row:
mysql> update tkmemberstage set sequence=sequence - 11 where tkmemberstage.ID = 4;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 29 |
+----+----------+
4 rows in set (0.00 sec)
Now if I run the SELECT part of the UPDATE statement I get exactly what we expect:
mysql> select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence;
+----+-------------+
| ID | newSequence |
+----+-------------+
| 1 | 10 |
| 2 | 20 |
| 4 | 30 |
| 3 | 40 |
+----+-------------+
4 rows in set (0.01 sec)
And yet when I run the final UPDATE statement itself here is the result:
mysql> update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
Query OK, 1 row affected (0.00 sec)
Rows matched: 4 Changed: 1 Warnings: 0
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
+----+----------+
4 rows in set (0.00 sec)
So the first obvious question is what changed in 5.7 that could/would cause this kind of behaviour.
(It's been consistent for well over 6 months now. I just patched the 5.7 server today and retested and still the same results. I also installed 5.7 on a AWS AMI (Cloud9) instance where I did these tests so this behaviour is now confirmed on numerous instances of 5.7.)
The second question is of course what exactly do we do about it?
The third, a nice to know, is how would we go deeper in troubleshooting this?
For what it is worth here is the EXPLAIN of the UPDATE on 5.7:
mysql> explain update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
| 1 | UPDATE | tkmemberstage | NULL | ALL | PRIMARY | NULL | NULL | NULL | 4 | 100.00 | NULL |
| 1 | PRIMARY | <derived2> | NULL | ref | <auto_key0> | <auto_key0> | 8 | well20180515.tkmemberstage.ID | 2 | 100.00 | NULL |
| 2 | DERIVED | tkmemberstage | NULL | ALL | tkmembershipID | NULL | NULL | NULL | 4 | 100.00 | Using where; Using temporary; Using filesort |
| 2 | DERIVED | <derived3> | NULL | ALL | NULL | NULL | NULL | NULL | 1 | 100.00 | Using join buffer (Block Nested Loop) |
| 3 | DERIVED | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used |
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
5 rows in set (0.00 sec)
Whereas here is the EXPLAIN on a non 5.7 version:
mysql> explain update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
| 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 2 | NULL |
| 1 | PRIMARY | tkmemberstage | eq_ref | PRIMARY | PRIMARY | 8 | constructedTableReordered.ID | 1 | NULL |
| 2 | DERIVED | <derived3> | system | NULL | NULL | NULL | NULL | 1 | Using filesort |
| 2 | DERIVED | tkmemberstage | ref | tkmembershipID | tkmembershipID | 8 | const | 1 | Using where |
| 3 | DERIVED | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used |
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
5 rows in set (0.03 sec)
mysql update query
asked 5 hours ago
Techmag
1185
New contributor
Techmag is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
1
I haven't checked, but while it certanly can be related to a versiln change, your update doesn't seem determunistic- could you add an order by to the update to discard that? Sometimes optimizer optimizations (or regressions) reveals bugs on the logic of a query- and yours look like one that would depend on the output order- which is not guarantee without an order by.
– jynus
4 hours ago
I'm not sure I understand. I do haveorder by tkmemberstage.sequence-- where else should an order by be inserted?
– Techmag
4 hours ago
AddedCREATEandINSERTas per request.tkmembershipIDis a foreign key for working with a "block" of records at one time.
– Techmag
3 hours ago
You mean:set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 99 order by sequence;
– Techmag
3 hours ago
Sorry -- am flipping between multiple databases/datasets -- It looks like the following works on 5.7:set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 1 order by sequence;- Next step is to update the code and run application level checks. Unsure why I would have chosen a more complex form however I suspect there was a reason at the time :) I might re-find that as I update the code...
– Techmag
3 hours ago
 |Â
show 1 more comment
up vote
3
down vote
favorite
up vote
3
down vote
favorite
I use a column called sequence on tables where I have to re-sort blocks of rows into an arbitrarily order.
CREATE TABLE `tkmemberstage` (
`ID` bigint(22) unsigned NOT NULL AUTO_INCREMENT,
`tkmembershipID` bigint(22) unsigned NOT NULL DEFAULT '0',
`sequence` int(11) NOT NULL DEFAULT '0',
PRIMARY KEY (`ID`),
KEY `tkmembershipID` (`tkmembershipID`)
)
insert into tkmemberstage set tkmembershipID = 1, sequence = 10;
insert into tkmemberstage set tkmembershipID = 1, sequence = 20;
insert into tkmemberstage set tkmembershipID = 1, sequence = 30;
insert into tkmemberstage set tkmembershipID = 1, sequence = 40;
A few years back I researched the following as a means of resequencing a block of rows in a single UPDATE
This works by creating an interim virtual table and then updating the entire block of rows in one transaction instead of having to write each row out programmatically.
The UPDATE statement goes like this:
update
tkmemberstage
join
(select tkmemberstage.ID,
(@newSequence := @newSequence+10) as newSequence
from
tkmemberstage
cross join
(select @newSequence := 0)
constructedTable
where
tkmemberstage.tkmembershipID = 1
order by tkmemberstage.sequence)
constructedTableReordered
on tkmemberstage.ID=constructedTableReordered.ID
set tkmemberstage.sequence=constructedTableReordered.newSequence;
I have copied it verbatim from a development server in order not to add any translation problems to the mix.
I currently have this running on a mix of RDS servers in the AWS cloud and on anything other than a 5.7 server it works as expected.
In troubleshooting this I tried to deconstruct the statement and try it in partial chunks.
Here is the dataset I'm working on:
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
+----+----------+
4 rows in set (0.00 sec)
I then perform an update to sequence on a single row:
mysql> update tkmemberstage set sequence=sequence - 11 where tkmemberstage.ID = 4;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 29 |
+----+----------+
4 rows in set (0.00 sec)
Now if I run the SELECT part of the UPDATE statement I get exactly what we expect:
mysql> select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence;
+----+-------------+
| ID | newSequence |
+----+-------------+
| 1 | 10 |
| 2 | 20 |
| 4 | 30 |
| 3 | 40 |
+----+-------------+
4 rows in set (0.01 sec)
And yet when I run the final UPDATE statement itself here is the result:
mysql> update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
Query OK, 1 row affected (0.00 sec)
Rows matched: 4 Changed: 1 Warnings: 0
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
+----+----------+
4 rows in set (0.00 sec)
So the first obvious question is what changed in 5.7 that could/would cause this kind of behaviour.
(It's been consistent for well over 6 months now. I just patched the 5.7 server today and retested and still the same results. I also installed 5.7 on a AWS AMI (Cloud9) instance where I did these tests so this behaviour is now confirmed on numerous instances of 5.7.)
The second question is of course what exactly do we do about it?
The third, a nice to know, is how would we go deeper in troubleshooting this?
For what it is worth here is the EXPLAIN of the UPDATE on 5.7:
mysql> explain update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
| 1 | UPDATE | tkmemberstage | NULL | ALL | PRIMARY | NULL | NULL | NULL | 4 | 100.00 | NULL |
| 1 | PRIMARY | <derived2> | NULL | ref | <auto_key0> | <auto_key0> | 8 | well20180515.tkmemberstage.ID | 2 | 100.00 | NULL |
| 2 | DERIVED | tkmemberstage | NULL | ALL | tkmembershipID | NULL | NULL | NULL | 4 | 100.00 | Using where; Using temporary; Using filesort |
| 2 | DERIVED | <derived3> | NULL | ALL | NULL | NULL | NULL | NULL | 1 | 100.00 | Using join buffer (Block Nested Loop) |
| 3 | DERIVED | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used |
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
5 rows in set (0.00 sec)
Whereas here is the EXPLAIN on a non 5.7 version:
mysql> explain update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
| 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 2 | NULL |
| 1 | PRIMARY | tkmemberstage | eq_ref | PRIMARY | PRIMARY | 8 | constructedTableReordered.ID | 1 | NULL |
| 2 | DERIVED | <derived3> | system | NULL | NULL | NULL | NULL | 1 | Using filesort |
| 2 | DERIVED | tkmemberstage | ref | tkmembershipID | tkmembershipID | 8 | const | 1 | Using where |
| 3 | DERIVED | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used |
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
5 rows in set (0.03 sec)
mysql update query
asked 5 hours ago
Techmag
1185
New contributor
Techmag is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I use a column called sequence on tables where I have to re-sort blocks of rows into an arbitrarily order.
CREATE TABLE `tkmemberstage` (
`ID` bigint(22) unsigned NOT NULL AUTO_INCREMENT,
`tkmembershipID` bigint(22) unsigned NOT NULL DEFAULT '0',
`sequence` int(11) NOT NULL DEFAULT '0',
PRIMARY KEY (`ID`),
KEY `tkmembershipID` (`tkmembershipID`)
)
insert into tkmemberstage set tkmembershipID = 1, sequence = 10;
insert into tkmemberstage set tkmembershipID = 1, sequence = 20;
insert into tkmemberstage set tkmembershipID = 1, sequence = 30;
insert into tkmemberstage set tkmembershipID = 1, sequence = 40;
A few years back I researched the following as a means of resequencing a block of rows in a single UPDATE
This works by creating an interim virtual table and then updating the entire block of rows in one transaction instead of having to write each row out programmatically.
The UPDATE statement goes like this:
update
tkmemberstage
join
(select tkmemberstage.ID,
(@newSequence := @newSequence+10) as newSequence
from
tkmemberstage
cross join
(select @newSequence := 0)
constructedTable
where
tkmemberstage.tkmembershipID = 1
order by tkmemberstage.sequence)
constructedTableReordered
on tkmemberstage.ID=constructedTableReordered.ID
set tkmemberstage.sequence=constructedTableReordered.newSequence;
I have copied it verbatim from a development server in order not to add any translation problems to the mix.
I currently have this running on a mix of RDS servers in the AWS cloud and on anything other than a 5.7 server it works as expected.
In troubleshooting this I tried to deconstruct the statement and try it in partial chunks.
Here is the dataset I'm working on:
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
+----+----------+
4 rows in set (0.00 sec)
I then perform an update to sequence on a single row:
mysql> update tkmemberstage set sequence=sequence - 11 where tkmemberstage.ID = 4;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 29 |
+----+----------+
4 rows in set (0.00 sec)
Now if I run the SELECT part of the UPDATE statement I get exactly what we expect:
mysql> select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence;
+----+-------------+
| ID | newSequence |
+----+-------------+
| 1 | 10 |
| 2 | 20 |
| 4 | 30 |
| 3 | 40 |
+----+-------------+
4 rows in set (0.01 sec)
And yet when I run the final UPDATE statement itself here is the result:
mysql> update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
Query OK, 1 row affected (0.00 sec)
Rows matched: 4 Changed: 1 Warnings: 0
mysql> select ID, sequence from tkmemberstage;
+----+----------+
| ID | sequence |
+----+----------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
+----+----------+
4 rows in set (0.00 sec)
So the first obvious question is what changed in 5.7 that could/would cause this kind of behaviour.
(It's been consistent for well over 6 months now. I just patched the 5.7 server today and retested and still the same results. I also installed 5.7 on a AWS AMI (Cloud9) instance where I did these tests so this behaviour is now confirmed on numerous instances of 5.7.)
The second question is of course what exactly do we do about it?
The third, a nice to know, is how would we go deeper in troubleshooting this?
For what it is worth here is the EXPLAIN of the UPDATE on 5.7:
mysql> explain update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
| 1 | UPDATE | tkmemberstage | NULL | ALL | PRIMARY | NULL | NULL | NULL | 4 | 100.00 | NULL |
| 1 | PRIMARY | <derived2> | NULL | ref | <auto_key0> | <auto_key0> | 8 | well20180515.tkmemberstage.ID | 2 | 100.00 | NULL |
| 2 | DERIVED | tkmemberstage | NULL | ALL | tkmembershipID | NULL | NULL | NULL | 4 | 100.00 | Using where; Using temporary; Using filesort |
| 2 | DERIVED | <derived3> | NULL | ALL | NULL | NULL | NULL | NULL | 1 | 100.00 | Using join buffer (Block Nested Loop) |
| 3 | DERIVED | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used |
+----+-------------+---------------+------------+------+----------------+-------------+---------+-------------------------------+------+----------+----------------------------------------------+
5 rows in set (0.00 sec)
Whereas here is the EXPLAIN on a non 5.7 version:
mysql> explain update tkmemberstage join (select tkmemberstage.ID,(@newSequence := @newSequence+10) as newSequence from tkmemberstage cross join (select @newSequence := 0) constructedTable where tkmemberstage.tkmembershipID = 1 order by tkmemberstage.sequence) constructedTableReordered on tkmemberstage.ID=constructedTableReordered.ID set tkmemberstage.sequence=constructedTableReordered.newSequence;
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
| 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 2 | NULL |
| 1 | PRIMARY | tkmemberstage | eq_ref | PRIMARY | PRIMARY | 8 | constructedTableReordered.ID | 1 | NULL |
| 2 | DERIVED | <derived3> | system | NULL | NULL | NULL | NULL | 1 | Using filesort |
| 2 | DERIVED | tkmemberstage | ref | tkmembershipID | tkmembershipID | 8 | const | 1 | Using where |
| 3 | DERIVED | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used |
+----+-------------+---------------+--------+----------------+----------------+---------+------------------------------+------+----------------+
5 rows in set (0.03 sec)
mysql update query
mysql update query
asked 5 hours ago
Techmag
1185
New contributor
Techmag is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 5 hours ago
Techmag
1185
New contributor
Techmag is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 4 hours ago
asked 5 hours ago
Techmag
1185
New contributor
Techmag is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 5 hours ago
Techmag
1185
asked 5 hours ago
Techmag
1185
1185
New contributor
Techmag is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Techmag is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Techmag is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
1
I haven't checked, but while it certanly can be related to a versiln change, your update doesn't seem determunistic- could you add an order by to the update to discard that? Sometimes optimizer optimizations (or regressions) reveals bugs on the logic of a query- and yours look like one that would depend on the output order- which is not guarantee without an order by.
– jynus
4 hours ago
I'm not sure I understand. I do haveorder by tkmemberstage.sequence-- where else should an order by be inserted?
– Techmag
4 hours ago
AddedCREATEandINSERTas per request.tkmembershipIDis a foreign key for working with a "block" of records at one time.
– Techmag
3 hours ago
You mean:set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 99 order by sequence;
– Techmag
3 hours ago
Sorry -- am flipping between multiple databases/datasets -- It looks like the following works on 5.7:set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 1 order by sequence;- Next step is to update the code and run application level checks. Unsure why I would have chosen a more complex form however I suspect there was a reason at the time :) I might re-find that as I update the code...
– Techmag
3 hours ago
 |Â
show 1 more comment
1
I haven't checked, but while it certanly can be related to a versiln change, your update doesn't seem determunistic- could you add an order by to the update to discard that? Sometimes optimizer optimizations (or regressions) reveals bugs on the logic of a query- and yours look like one that would depend on the output order- which is not guarantee without an order by.
– jynus
4 hours ago
I'm not sure I understand. I do haveorder by tkmemberstage.sequence-- where else should an order by be inserted?
– Techmag
4 hours ago
AddedCREATEandINSERTas per request.tkmembershipIDis a foreign key for working with a "block" of records at one time.
– Techmag
3 hours ago
You mean:set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 99 order by sequence;
– Techmag
3 hours ago
Sorry -- am flipping between multiple databases/datasets -- It looks like the following works on 5.7:set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 1 order by sequence;- Next step is to update the code and run application level checks. Unsure why I would have chosen a more complex form however I suspect there was a reason at the time :) I might re-find that as I update the code...
– Techmag
3 hours ago
1
1
I haven't checked, but while it certanly can be related to a versiln change, your update doesn't seem determunistic- could you add an order by to the update to discard that? Sometimes optimizer optimizations (or regressions) reveals bugs on the logic of a query- and yours look like one that would depend on the output order- which is not guarantee without an order by.
– jynus
4 hours ago
I haven't checked, but while it certanly can be related to a versiln change, your update doesn't seem determunistic- could you add an order by to the update to discard that? Sometimes optimizer optimizations (or regressions) reveals bugs on the logic of a query- and yours look like one that would depend on the output order- which is not guarantee without an order by.
– jynus
4 hours ago
I'm not sure I understand. I do have
order by tkmemberstage.sequence -- where else should an order by be inserted?– Techmag
4 hours ago
I'm not sure I understand. I do have
order by tkmemberstage.sequence -- where else should an order by be inserted?– Techmag
4 hours ago
Added
CREATE and INSERT as per request. tkmembershipID is a foreign key for working with a "block" of records at one time.– Techmag
3 hours ago
Added
CREATE and INSERT as per request. tkmembershipID is a foreign key for working with a "block" of records at one time.– Techmag
3 hours ago
You mean:
set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 99 order by sequence;– Techmag
3 hours ago
You mean:
set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 99 order by sequence;– Techmag
3 hours ago
Sorry -- am flipping between multiple databases/datasets -- It looks like the following works on 5.7:
set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 1 order by sequence; - Next step is to update the code and run application level checks. Unsure why I would have chosen a more complex form however I suspect there was a reason at the time :) I might re-find that as I update the code...– Techmag
3 hours ago
Sorry -- am flipping between multiple databases/datasets -- It looks like the following works on 5.7:
set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 1 order by sequence; - Next step is to update the code and run application level checks. Unsure why I would have chosen a more complex form however I suspect there was a reason at the time :) I might re-find that as I update the code...– Techmag
3 hours ago
 |Â
show 1 more comment
1 Answer
1
active
oldest
votes
up vote
2
down vote
accepted
The problem is likely caused by one of these - or both:
Lack of matching index for the query - on
(tkmembershipID, sequence). Without this index (and any index), the optimizer will likely choose a table scan.Optimization improvements on version 5.7. I've seen similar issues in other flavours (call me Maria) where an optimization improvement caused a query to use a different plan. Specifically, (after either version 5.3 or 5.5) MariaDB's optimizer knew that
ORDER BYin subqueries is redundant, so it could be "optimized away".If a similar thing happens here, and the plan used gets rid of the
ORDER BY, that explains the results.(And that may be considered a bug - as it changes your expected outcome when using variables. You can file a bug report to MySQL, with your situation and they may be able to fix it - or suggest a different solution/workaround).
In the mean time, I suggest you add the index mentioned above and check the plans again.
By the way, it seems like your query can be simplified to:
set @newSequence = 0 ;
update tkmemberstage
set sequence = (@newSequence := @newSequence + 10)
where tkmembershipID = 1
order by sequence ;
answered 3 hours ago
ypercubeᵀᴹ
72.5k11120195
add a comment |Â
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
2
down vote
accepted
The problem is likely caused by one of these - or both:
Lack of matching index for the query - on
(tkmembershipID, sequence). Without this index (and any index), the optimizer will likely choose a table scan.Optimization improvements on version 5.7. I've seen similar issues in other flavours (call me Maria) where an optimization improvement caused a query to use a different plan. Specifically, (after either version 5.3 or 5.5) MariaDB's optimizer knew that
ORDER BYin subqueries is redundant, so it could be "optimized away".If a similar thing happens here, and the plan used gets rid of the
ORDER BY, that explains the results.(And that may be considered a bug - as it changes your expected outcome when using variables. You can file a bug report to MySQL, with your situation and they may be able to fix it - or suggest a different solution/workaround).
In the mean time, I suggest you add the index mentioned above and check the plans again.
By the way, it seems like your query can be simplified to:
set @newSequence = 0 ;
update tkmemberstage
set sequence = (@newSequence := @newSequence + 10)
where tkmembershipID = 1
order by sequence ;
answered 3 hours ago
ypercubeᵀᴹ
72.5k11120195
add a comment |Â
up vote
2
down vote
accepted
The problem is likely caused by one of these - or both:
Lack of matching index for the query - on
(tkmembershipID, sequence). Without this index (and any index), the optimizer will likely choose a table scan.Optimization improvements on version 5.7. I've seen similar issues in other flavours (call me Maria) where an optimization improvement caused a query to use a different plan. Specifically, (after either version 5.3 or 5.5) MariaDB's optimizer knew that
ORDER BYin subqueries is redundant, so it could be "optimized away".If a similar thing happens here, and the plan used gets rid of the
ORDER BY, that explains the results.(And that may be considered a bug - as it changes your expected outcome when using variables. You can file a bug report to MySQL, with your situation and they may be able to fix it - or suggest a different solution/workaround).
In the mean time, I suggest you add the index mentioned above and check the plans again.
By the way, it seems like your query can be simplified to:
set @newSequence = 0 ;
update tkmemberstage
set sequence = (@newSequence := @newSequence + 10)
where tkmembershipID = 1
order by sequence ;
answered 3 hours ago
ypercubeᵀᴹ
72.5k11120195
add a comment |Â
up vote
2
down vote
accepted
up vote
2
down vote
accepted
The problem is likely caused by one of these - or both:
Lack of matching index for the query - on
(tkmembershipID, sequence). Without this index (and any index), the optimizer will likely choose a table scan.Optimization improvements on version 5.7. I've seen similar issues in other flavours (call me Maria) where an optimization improvement caused a query to use a different plan. Specifically, (after either version 5.3 or 5.5) MariaDB's optimizer knew that
ORDER BYin subqueries is redundant, so it could be "optimized away".If a similar thing happens here, and the plan used gets rid of the
ORDER BY, that explains the results.(And that may be considered a bug - as it changes your expected outcome when using variables. You can file a bug report to MySQL, with your situation and they may be able to fix it - or suggest a different solution/workaround).
In the mean time, I suggest you add the index mentioned above and check the plans again.
By the way, it seems like your query can be simplified to:
set @newSequence = 0 ;
update tkmemberstage
set sequence = (@newSequence := @newSequence + 10)
where tkmembershipID = 1
order by sequence ;
answered 3 hours ago
ypercubeᵀᴹ
72.5k11120195
The problem is likely caused by one of these - or both:
Lack of matching index for the query - on
(tkmembershipID, sequence). Without this index (and any index), the optimizer will likely choose a table scan.Optimization improvements on version 5.7. I've seen similar issues in other flavours (call me Maria) where an optimization improvement caused a query to use a different plan. Specifically, (after either version 5.3 or 5.5) MariaDB's optimizer knew that
ORDER BYin subqueries is redundant, so it could be "optimized away".If a similar thing happens here, and the plan used gets rid of the
ORDER BY, that explains the results.(And that may be considered a bug - as it changes your expected outcome when using variables. You can file a bug report to MySQL, with your situation and they may be able to fix it - or suggest a different solution/workaround).
In the mean time, I suggest you add the index mentioned above and check the plans again.
By the way, it seems like your query can be simplified to:
set @newSequence = 0 ;
update tkmemberstage
set sequence = (@newSequence := @newSequence + 10)
where tkmembershipID = 1
order by sequence ;
answered 3 hours ago
ypercubeᵀᴹ
72.5k11120195
edited 3 hours ago
answered 3 hours ago
ypercubeᵀᴹ
72.5k11120195
answered 3 hours ago
ypercubeᵀᴹ
72.5k11120195
answered 3 hours ago
ypercubeᵀᴹ
72.5k11120195
72.5k11120195
add a comment |Â
add a comment |Â
Techmag is a new contributor. Be nice, and check out our Code of Conduct.
Techmag is a new contributor. Be nice, and check out our Code of Conduct.
Techmag is a new contributor. Be nice, and check out our Code of Conduct.
Techmag is a new contributor. Be nice, and check out our Code of Conduct.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fdba.stackexchange.com%2fquestions%2f220841%2fan-update-runs-unexpectedly-on-mysql-5-7-whereas-it-runs-as-expected-on-prior-ve%23new-answer', 'question_page');
);
Post as a guest
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
1
I haven't checked, but while it certanly can be related to a versiln change, your update doesn't seem determunistic- could you add an order by to the update to discard that? Sometimes optimizer optimizations (or regressions) reveals bugs on the logic of a query- and yours look like one that would depend on the output order- which is not guarantee without an order by.
– jynus
4 hours ago
I'm not sure I understand. I do have
order by tkmemberstage.sequence-- where else should an order by be inserted?– Techmag
4 hours ago
Added
CREATEandINSERTas per request.tkmembershipIDis a foreign key for working with a "block" of records at one time.– Techmag
3 hours ago
You mean:
set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 99 order by sequence;– Techmag
3 hours ago
Sorry -- am flipping between multiple databases/datasets -- It looks like the following works on 5.7:
set @newSequence = 0 ; update tkmemberstage set sequence = (@newSequence := @newSequence + 10) where tkmembershipID = 1 order by sequence;- Next step is to update the code and run application level checks. Unsure why I would have chosen a more complex form however I suspect there was a reason at the time :) I might re-find that as I update the code...– Techmag
3 hours ago