Hi,
When using views built with left joins, and then querying against these
views, there are a lot of join in the plan that are not necessary, because I
don't select/use any column of each table in the views every time. Tables
that are left joined and never referenced anywhere else in the query
Sorry, I have left out the PK requirement.
What Nicolas wrote is right, I also use an O/R mapper and inheritance is
solved with vertical partitioning. The tables are connected to each other
with the PK. And the mapper defines views for each class with left joins.
The mapper generates queries
, Ottó Havasvölgyi [EMAIL PROTECTED]:
My simple example:
Class hierarchy and fields:
Shape (ID, X, Y)
|
+-Circle (ID, Radius)
|
+-Rectangle (ID, Width, Height)
The mapper creates 3 tables with the columns next to the class name.
And it creates 3 views. One of them:
RectangleView: SELECT
sometimes will
query for the status description, sometimes not.
I suspect that checking to see if tables have the right unique keys
or RI would add a noticeable amount of extra work to query planning,
so we might want a GUC to disable it.
On Apr 7, 2007, at 12:45 PM, Ottó Havasvölgyi wrote:
Sorry
Hi,
Could you Bruce please add a TODO item for this feature?
The description could look something like this:
Eliminate the table T from the query/subquery if the following requirements
are satisfied:
1. T is left joined
2. T is referenced only in the join expression where it is left joined
3.
But then what about the null values? Perhaps unique + notnull is better?
Otto
2007/4/20, Nicolas Barbier [EMAIL PROTECTED]:
2007/4/16, Ottó Havasvölgyi [EMAIL PROTECTED]:
Eliminate the table T from the query/subquery if the following
requirements
are satisfied:
1. T is left joined
2. T
