>Jerome Fillon wrote:
>> Matthew Pascoe wrote in message <68p0mb$1...@forums.borland.com>...
>> >I am using Interbase 4.2 for NT. In my database creation script I have
>> >manually created an index for every primary and foreign key in each
table.
>> I
>> >have just read somewhere that Interbase automatically generates these.
Is
>> >this true? If so, what negative effects will these additional duplicate
>> >indexes cause.
>> >Thanks,
>> >Matthew Pascoe.
>> I used to work with IB 4.2 and make a lot of tables and primary and
foreign
>> keys, but i never heard about IB genrating them, maybe if you put the
same
>> field name in two tables but i'm not sure...because how IB does to find
the
>> master and the detail table ?
>> Don't be afraid because you can't create two primary key on the same
table!
>> So... no problems.
>> If you put indexes on indexed fields nothing will happen except that when
>> inserting it will update the two indexes, and then you will lose time and
>> space.
>This sage piece of advice is unfortunately very incorrect for Interbase.
In
>fact, you should do precisely the opposite and remove the explicitly
created
>indexes.
>IB does create an index on the table to manage a foreign-key, a primary
key,
>or a referential integrity relationship. Therefore you do not need to
create
>one. But, more to the point, you should NOT create one.
>The IB4 query-optimizer tends to generate plans that use all available
>indexes, even if two or more of these indices are redundant and even if
this
>causes the query to slow down - which it does.
>There are a number of highly relevant papers concerning Interbase at:
>http://www.mers.com/
