Pythian Group

One common question I get is how to use partitioning instead of MERGE tables. The process I use involves using stored procedures to create and drop partitions. This article will go over the stored procedures I use; special thanks to Roland Bouman for taking a look and giving great feedback to optimize this process.

First, a simple table, not partitioned (yet):

use test;
DROP TABLE IF EXISTS my_part;
CREATE TABLE IF NOT EXISTS my_part (
  id int NOT NULL,
  creationDate datetime NOT NULL,
  PRIMARY KEY (id,creationDate)
) ENGINE=InnoDB;

In real, life there is more to the table than just id and creationDate. The most important part is that the partitioned field(s) need to be part of the primary key.
Read the rest of this entry . . .

It’s probably worth some explanation to understand where I want to drive you: when you run an update in Oracle, the changes are made at the point that is consistent during the whole execution of the update. This allows you to run a command like the one below, even if ID is the primary key of T:

update t
  set id=(case id
             when 1 then 2
             when 2 then 1
             end)
  where id in (1,2);

If that was not the case, you would have to DEFER the constraint validation to the commit time every time you ran a command like the one above, or you would get an error like:

ORA-00001: unique constraint T_PK violated

To read more about how updates work in Oracle, look at Tom Kyte’s Write Consistency Part I, Part II, Seeing a Restart, and Part III, Why is a Restart Important to Us. But that’s a tangent to the subject of this post. What I’ll show here is that you can run a DELETE and an INSERT as parts of the same statement.

Read the rest of this entry . . .