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From "Greg Monroe" <Greg.Mon...@DukeCE.com>
Subject RE: Interface for Criteria and Criteria.Criterion
Date Tue, 31 Jan 2006 22:43:26 GMT
As I've said, I'm not tightly tied to this Frankenstien of
an interface, it was done by simply extracting all methods
that might be used by other objects (e.g., most of the get*
methods) and then finding the ones that caused compile error
when the interface was used.

I agree with most of your trimming, some minor IMHO 
exceptions are:

equals(..) should be there because it reminds implimenters
they need to override the default method to ensure criteria
can be compared.

setOffset/setLimit - Since these are used to perform paged
queries, it seems like they need to be available to any
classes needing to generate a sequence of paged queries.

That said, can you expand on your two Interfaces?  E.g,
some example methods/uses.

One question that comes to mind is that if we are 
contemplating some major internal rework, does there 
need to be criterion at all?  Doesn't it exist just
because the map implimentation does not allow for the
same column to be used twice. If this is changed, 
couldn't criteria implimentors be used where criterion
are currently used. 

Hmm, maybe another way to think about it is that 
the "where map" that criteria contains is required
to be all criterion objects.

Criterion then becomes a container for SQL expressions 
by having getColumn() return an Object (allowing for 
functions, aliased tables, and the like) and getValue 
would allow for functions, subqueries (a criteria object?), 
simple values, and the like.  With the job of figuring out 
how to render the objects handled by SQLBuilder.

Well enough rambling.. hopefully this makes sense.


> -----Original Message-----
> From: Thomas Fischer [mailto:tfischer@apache.org] 
> Sent: Saturday, January 28, 2006 5:54 AM
> To: torque-dev@db.apache.org
> Subject: Interface for Criteria and Criteria.Criterion
> This is continuing the discussion I had with Greg Monroe on 
> creating an 
> interface to access Criteria and Criteria.Criterion from the other
> Torque classes. See
> http://issues.apache.org/scarab/issues/id/TRQS341
> for Greg's suggestion and previous discussion
> > IMHO, it is a good idea to have a well define interfaces 
> (or an abstract 
> > class) between major areas of responsiblity. In the long 
> run, this helps 
> > keep the areas from stepping on each other and helps in testing, 
> > debugging, and enhancing the areas separate from each other.
> This is certainly a good point, I agree to that. But now it 
> comes to what 
> areas of responsibilities we want to define by the interfaces you 
> suggested. I can see two main ideas in your 
> CriteriaInterface. The first 
> is "1) A provider of information for composing an SQL Query", 
> the second 
> is "2) An object defining the contents of an SQL 
> insert/update/delete". 
> Here are the methods that do not fit into 1):
> CriteriaInterface.getNewCriterion(), CriteriaInterface.setLimit(), 
> CriteriaInterface.setOffset(), CriteriaInterface.remove(), 
> CriteriaInterface.add(), CriteriaInterface.addSelectColumn()
> The setLimit() and setOffset() methods are only used by 
> LargeSelect(), 
> they also do not fit into the pattern 2).
> Then there are methods which are just convenience methods:
> CriteriaInterface.getColumnName(), CriteriaInterface.getComparison(), 
> CriteriaInterface.getTableName(),CriteriaInterface.getValue()
> The methods
> CriteriaInterface.getFloat(), CriteriaInterface.getDouble()...
> are both convenience methods and are an overshot at the only 
> place they
> are used (VillageUtils.setVillageValue), a simple cast would be enough
> there.
> Then, there are methods you have marked yourself as 
> deprecated and are not 
> used anymore:
> CriteriaInterface.getJoinL(), CriteriaInterface.getJoinR()
> The equals() method is defined by any java Object and does 
> not need to be 
> included in an interface declaration.
> And, to make the list complete, including something I have 
> said before: 
> The "extends Map" in the CriteriaInterface exposes an implementation 
> detail and should be avoided (I do hope we do not use it anywhere).
> So my suggestion would be to split the CriteriaInterface in two 
> interfaces: QueryDataProvider(used for selects and deletes) and 
> UpdateDataProvider(used for updates and inserts), and remove 
> the methods I 
> have mentioned above which are cluttering up the interface. The idea 
> between splitting is that we would have reasonably small 
> interfaces with 
> well defined uses. Also, we would be to be able to use a 
> separate object 
> for updates/inserts at some point.
> If this seems reasonable, then we would also have to create 
> two Criterion 
> Interfaces: QueryDataConstraint and UpdateDataElement.
> The Criterion Interface has more methods which are needed by 
> other Torque 
> classes but do not fit into the above pattern. This is because the 
> Criterion still renders itself in SQL. If this is factored 
> out (as was 
> already done in the Criteria class), these methods can be removed. My
> suggestion would be to move the SQL rendering code to 
> the SQLBuilder class.
> Because this would also affect the interface to be created, I would 
> suggest to make Criterion a static inner class of Criteria. 
> The reference 
> from Criterion to its enclosing Criterion object is that it uses the 
> Criteria's DB object, and as a default of the ignoreCase 
> setting if no 
> specific ignoreCase is set for the criterion. Both is only 
> neede for SQL 
> rendering, and could be accessed there by providing the 
> enclosing Criteria 
> as additional argument.
> In my opinion, Greg's suggestion plus the changes outlined 
> above would 
> clear up the internal structure of the Criteria mechanism a lot. Any 
> opinions ?
>      Thomas
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