I'd like to partition an existing table into 3 partitions. At the time of update of our solution, a powershell script will connect to the MySQL server and execute a script file.
I tried following query for adding the partitions:
Alter Table `mytable`
PARTITION BY RANGE (TO_DAYS(`TimeStart`))
(
PARTITION start VALUES LESS THAN (0),
PARTITION "from"+(curdate()+0) VALUES LESS THAN (curdate()+1),
PARTITION future VALUES LESS THAN MAXVALUE
);
column timestart (datetime(3) NOT NULL) is part of the primary key.
The partition in the middle requires specific values to make it compatible with maintenance queries run from a Windows service at some interval.
The query fails for two different reasons:
Creation of the name of the partition: I'd like to get e.g. "from20180220" when the script was executed today.
The error messsage is
Error Code: 1064. You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"from"+(curdate()+0) VALUES LESS THAN (curdate()+1), PARTITION future ' at line 5
Creation of the partition value. When the script is run today (Feb 19), I'd like to have an equivalent to VALUES LESS THAN (TO_DAYS('2018-2-20').
Error Code: 1064. Constant, random or timezone-dependent expressions in (sub)partitioning function are not allowed near '), PARTITION future VALUES LESS THAN MAXVALUE )' at line 5
I tried TO_DAYS(curdate())+1 also. Actually, I did not expect MySQL to have closures...
How can those errors be solved?
You're attempting to use MySQL data-manipulation-language functions like CURDATE() and TO_DAYS() in your data definition code. You Can't Do That™.
You need to write some sort of program to write out a little file containing your Alter Table command, then run that file in MySQL.
Explanations from O.Jones are a bit too short.
You need to use another language script, like php, perl, python ...
Then write something like would work :
Alter Table `mytable`
PARTITION BY RANGE (TO_DAYS(`TimeStart`))
(
PARTITION start VALUES LESS THAN (0),
PARTITION from".$curdate." VALUES LESS THAN TO_DAYS(".$nextdateTime."),
PARTITION future VALUES LESS THAN MAXVALUE
);
Related
I come from an Apache Hive background.
In that language, you would say the below to insert into date 20220601:
insert into table db.tablename partition(date=20220601)
In MySQL; I can't get such an insert statement to work. I have been Googling & it seems it just sorts itself out?
So if I did
insert into db.tablename
select * from db.othertable
Would it automatically partition the ingested data?
I feel like I am missing something here!
If the table is partitioned, the values you insert determine which partition the row goes into. Partitioning a table requires you define the mapping, so it's always deterministic which partition a row goes into.
Therefore you don't need to tell INSERT which partition to insert the row into. It's determined automatically by the values you insert in the row.
Partitioning in MySQL is not required for a table. By default, a table is not partitioned. This is normal and sufficient in almost all cases.
Perhaps partitioning in Apache Hive is necessary and does something different from the feature called partitioning in MySQL? I don't know Apache Hive, so I can't answer that.
I suggest you read the MySQL manual chapter about partitioning if you want to learn more about it: https://dev.mysql.com/doc/refman/8.0/en/partitioning.html
I'm using mysql 5.6.16 and now want to change a partition name. I cannot find rename partition syntax, and it is inefficient to use statement as below:
alter table name reorganize partition old into ( partition new ...).
I got it by the way of exchange pasrtition. Firstly, I exchange the data in the partition to a normal empty table, Secondly, I reorganize the empty partition to wanted name. Finally, I exhchange the data with the normal table again
I have trouble for my project using mysql, i want to create Auto Increment in view table, i create sintax like this one:
SELECT
concat(#AI:= #AI + 1,`code`)
FROM
`TEST TABLE`, (SELECT #AI:=0) as `AI`
Why if i add syntax in first line like this one:
CREATE VIEW `TEST VIEW` as
I have some error :
How fix it, or other method for this?. thanks for advance!
If you were using Oracle, you would use an object called a sequence for this purpose. But, who has the money for Oracle licenses?
If you need a series of numbers and you're using the MariaDB fork, you can do
SELECT seq FROM seq_0_to_99
or some such use of the SEQUENCE engine.
If you need persistent sequence numbers in MySQL, here's a workaround. It's a kludge: If you create the following table:
CREATE TABLE sequence ( /*MySQL*/
sequence_id BIGINT NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`sequence_id`)
)
Then issue these three queries one after the other:
INSERT INTO sequence () VALUES (); /*MySQL*/
DELETE FROM sequence WHERE sequence_id < LAST_INSERT_ID();
SELECT LAST_INSERT_ID() AS sequence;
The third query is guaranteed to return a unique sequence number. This guarantee holds even if you have dozens of different client programs connected to your database. (The DELETE query merely keeps this otherwise pointless table from taking up too much space.)
The error message you received makes it clear that you can't use a session variable in a view.
https://dev.mysql.com/doc/refman/5.7/en/create-view.html says:
A view definition is subject to the following restrictions:
The SELECT statement cannot refer to system variables or user-defined variables.
You can't create a view for your query. You'll have to execute the query directly. The only other suggestion I can make is to develop a stored procedure for the query.
It sounds like you want to create a row number for a query result, not an auto-increment column to store in the table.
MySQL 8.0.2 has added the window function ROW_NUMBER(), but 8.0 is still under development as we're writing this. Perhaps in 2018 it will be finished and released as GA.
Hey I'm having an issue with altering table partitions using JDBI. Here is an example of the query I'm trying to run:
ALTER TABLE table1 DROP PARTITION P_1
This runs fine in MySQL when dropping the partition "P_1" from the table "table1."
I've implemented it in my java code as the following:
#SqlUpdate("ALTER TABLE table1 DROP PARTITION :partition;")
public void deletePartition(#Bind("partition") String partition);
And call this function as such
deletePartition("P_1")
However, this results in the following error:
Causing: org.skife.jdbi.v2.exceptions.UnableToExecuteStatementException: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''P_1'' at line 1 [statement:"ALTER TABLE table1 DROP PARTITION :partition;", located:"ALTER TABLE table1 DROP PARTITION :partition;", rewritten:"/* HiveDropBoxDBI.deletePartition */ ALTER TABLE table1 DROP PARTITION ?;", arguments:{ positional:{}, named:{partition:'P_1'}, finder:[]}]
Is this functionality not supported? Or am I missing something with my syntax?
Thanks
We need to use #Define for changing the query. #Bind is only for used for binding parameters (like some_field = :value).
#SqlUpdate("ALTER TABLE table1 DROP PARTITION :partition;")
public void deletePartition(#Bind("partition") String partition);
You can't use bind parameters for DDL such as CREATE, ALTER and DROP.
In order to drop your partition, you must concatenate the partition name onto the query instead.
However, taking a partition name and appending it straight into a SQL string which gets executed is a recipe for a security vulnerability. Consider some of the following:
'escaping' the partition name with backticks,
checking that the partition name contains only certain whitelisted characters (e.g. alphanumerics and underscores),
querying the INFORMATION_SCHEMA.PARTITIONS table to see if the partition you're trying to drop exists. (This might not be a good idea if there is a chance that the partition may be created or dropped between checking for its existence and dropping it. I don't know your application well enough to say whether this would be a problem.)
As JDBI relies on constant strings for #SqlUpdate annotations, you will not be able to use JDBI in this way to drop partitions, unless you only ever want to drop the same partition.
I am using MySQL and here is a simple query set:
create table dcheck (
fdate date,
sdate date,
check (fdate <= sdate)
);
insert into dcheck values ('2006-12-12','2003-12-12');
insert into dcheck values ('2003-12-12', '2006-12-12');
Here I expect the first insert statement to fail. But surprisingly, both the queries passes and two rows are there in the table.
Can anyone please explain why?
Thanks
MySQL doesn't implement CHECK constraints. From the latest (5.6) fine manual:
The CHECK clause is parsed but ignored by all storage engines.
So the syntax is parsed for compatibility other other SQLs but the checking is not implemented.
You could fake your CHECK constraint with BEFORE INSERT and BEFORE UPDATE triggers that threw an exception if the desired condition was not met.
The CHECK clause is parsed but ignored by all storage engines.
http://dev.mysql.com/doc/refman/5.1/en/create-table.html
CHECK constraints are now supported since MySQL 8.0.16