I have a hypothetical table with a primary key that is a BIGINT. Let's say my table grows very large and I have to partition and create different partitions by date range. What happens with primary key? Does that mean I can exceed the capacity of the BIGINT since there are more tables now? How does MySQL keep from assigning duplicate primary keys assuming a BIGINT set to auto increment a unique value?
Thanks in advance...
Partitioning doesn't create a new table. There is still one table with many partitions. Auto increment unique value keeps it functionality. Data grouped in partitions by date field that you choose to create partitions with.
Take a look at this : http://dev.mysql.com/tech-resources/articles/mysql_55_partitioning.html
Related
I have a database which use sequence number as its primary key. Other than there is a column called "date_time" which can be duplicated.
Now I need to make partitions by using date_time as follows.
ALTER TABLE data
PARTITION BY RANGE (TO_DAYS('date_time')) (
PARTITION p20220103 VALUES LESS THAN (TO_DAYS('2022-01-04 00:00:00')),
PARTITION p20220104 VALUES LESS THAN (TO_DAYS('2022-01-05 00:00:00')),
PARTITION p20220105 VALUES LESS THAN MAXVALUE
);
Since the date_time is not a primary key in data table, I couldn't create partitions.
ERROR 1503 (HY000): A PRIMARY KEY must include all columns in the table's partitioning function (prefixed columns are not considered).
How should I create partitions without adding date_time as a primary key?
You cannot. The rule is simple, stated in https://dev.mysql.com/doc/refman/8.0/en/partitioning-limitations-partitioning-keys-unique-keys.html:
Every unique key on the table must use every column in the table's partitioning expression.
If the table has a primary key or unique key but that key does not include the column(s) in the partitioning expression, then it cannot enforce uniqueness when you insert a new row without checking every partition for duplicates.
The only way around this, to allow a column like your date_time to be the partitioning expression, is to define the table with no primary or unique key.
This has its own hazards. You may need a unique key so you can address rows individually to update or delete them. Also row-based replication becomes very inefficient if your table has no primary key.
This usually means you cannot partition the table by date_time, or even that you cannot partition the table at all. But this isn't always a bad thing. Partitioning doesn't necessarily give a great benefit. Partitioning can even cause more complexity, because you may have queries that would be bound to search every partition anyway.
Partitioning is not a cure-all, and frequently is a liability.
I have a bunch of huge tables that don't have primary keys. (Don't ask me why) I will append an 'id' field to each table. It will be an integer type. Later, I will promote it to a non-null, unique-value index, and a primary key.
My question: Is there a way in MySQL (5 ish) We have about a hundred tables, and the largest among them have over 1 million records. After creating the new 'id' column, is there a way to have MySQL backfill (ie, add a value to the existing records) the 'id' field? I would rather be able to do this all in MySQL. Otherwise I will have to write a PHP script to populate the existing records.
Thanx, Don!
If you do a
ALTER TABLE table1 ADD COLUMN id INTEGER NOT NULL auto_increment PRIMARY KEY
It will auto populate your table with a auto_incrementing primary key.
Might take a while on a large table.
I Have 2 Question
If my table contain a unique column like this:
DROP TABLE IF EXISTS TestTable;
CREATE TABLE TestTable(
ID INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
GUID VARCHAR(32) UNIQUE NULL);
Do i Need to create an Index for this GUID column.
Note: i have GUID column In Where statement with join tables
My Second Question is the update statement will effect the index table if the updated column(s) not have been indexes?
No, UNIQUE is kind of index, so you don't need another index on the same column.
It won't update the index, if the changed column is not indexed.
Indexes that are not changed do not get updated.
source
It depends on which database you are using. Different databases have different ways of indexing.
If you are using InnoDB then the Primary Key and Unique Key is already an index, so you won't need to. If you create manually yet another index for the GUID column then you will have an extra redundant index on that column which wastes space.
I'm working on designing a new database that will need to handle an enormous amount of data. It will be a data warehouse system, and will thus be organized around a central hub table:
create table hub(id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
date_time DATETIME NOT NULL, bit_of_data INT NOT NULL);
When this table grows very large, it seems that it will be necessary to partition it based on the 'date_time' column, with each partition being, say, one month of data. However, there will also be another table:
create table other_data(id BIGINT NOT NULL PRIMARY KEY,
more_data INT NOT NULL, FOREIGN KEY(id) REFERENCES hub(id));
This second table will contain records for about 90% of the ids that appear in the main 'hub' table. I'd like to partition the 'other_data' table as well as the 'hub' table, and have the partitions basically match up with each other. Is there any way to partition the 'hub' table on a date range, and then also partition the 'other_data' table on the same date range?
Thanks!
This can be done only by adding a (redudant) date column in the other_data table.
I would like to convert some of our MyISAM tables to InnoDB so I can take advantage of foreign key support. However, most of the tables use a two-column (composite) primary key design in which one of those columns is an auto-increment (this was done for historical reasons and also ensured that the auto-increment column could act as a kind of incremental key for records within the context of the other column's value)
I realize that we need to do away with the multi-column primary key in order to use auto-increment and InnoDB. We have thousands of records though and these records have relationships to other tables.
Are there any tips on how to convert these tables to InnoDB? The only method I've come up with is to first add a new column in each table, set it as the sole auto-increment primary key and then use scripts to update the dependent tables to point to the new (truly unique) primary key.
Thanks
Steve
In MySQL 5.0 and greater versions you can include the auto-increment column as part of the primary key, but it has to be the first field in the index.
*...An AUTO_INCREMENT column must appear as the first column in an index on an InnoDB table...*
Check the documentation entry here http://dev.mysql.com/doc/refman/5.0/en/innodb-auto-increment-handling.html