Subject: sequence-block pattern 2004-06-18 - By Navjot Singh
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hi koala,
Usually, longer indices means larger number of RRs can be located
*directly*. But that also means index table is BIG too.
Try to create an index over 2 columns. Would your index table size be
bigger or smaller thatn the one you create over 1 column? Look into ISAM
structures, you will get to know more.
So, whenever you insert/update/delete, the queries will take longer. As
along RR, the index table also to be looed up and updated.
> I have implemented the sequence block pattern just to better understand it.
> I know that the use of long values as primary key is a good choice
> because it reduce the size of index tables and improve performance.
seems like patterns are getting too much :-)
> This patters has several drawbacks, for example the real primary key
> should be defined as UNIQUE and others stuff reported in EJBDesign
> Pattern book.
Primary key IS UNIQUE. What's the drawback here?
> Now I have a design question. If I have a DB schema with a set of table,
> is it a good choice use a long id as primary key for all the tables?
> When it could be necessary use long ids as primary keys? In which cases
> I should avoid this?
Wrong way to look at PKs. usually people keep one of smallest CANDIDATE
Keys as primary key. Many people dont worry much about them and just
keep auto_increment / sequence column as PK.
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