You can save storage by just quote Max Ross's article...
http://gae-java-persistence.blogspot.com/2009/11/case-insensitive-queries.html
On Mar 23, 12:27 am, Gleidson - MG - Brasil
<gleidson.gmo...@gmail.com> wrote:
> If you're using a relational database it's pretty easy to execute case-
> insensitive queries because it's a native feature of the database. It
> usually looks something like this:
>
> select * from Person where UPPER(lastName) = 'ROSS'
>
> This is a challenge for the App Engine Datastore because we rely on
> executing scans over a limited subset of your data and returning
> results as we encounter them. Consider the following strings in
> lexicographic order:
> ...
> ROSE
> ...
> ROSS
> ...
> ROSTA
> ...
> Rose
> ...
> Ross
> ...
> Rosta
> ...
> rose
> ...
> ross
> ...
> rosta
> ...
>
> As you can see there could be an unlimited number of rows in between
> 'ROSS' and 'Ross', and also between 'Ross' and 'ross' (okay not
> unlimited, we do have a limit on indexed string length, but definitely
> Large), so if we start scanning at 'ROSS' we might have to skip a huge
> number of results before we hit 'Ross', and that doesn't scale. This
> is why the datastore doesn't support case-insensitive queries.
>
> Fortunately it's not hard to implement support for case-insensitive
> queries in your application. Here's the approach: for each field that
> you want to query in a case-insensitive way, create a duplicate field
> that stores the value of that field in either all upper or lowercase
> letters. Then, have your model object register a pre-persist callback
> with your persistence framework (JPA or JDO), and then populate the
> duplicate fields inside that callback. Here's what it looks like.
>
> JPA:
> import javax.persistence.PrePersist;
> import javax.persistence.PreUpdate;
>
> @Entity
> public class Person {
> @Id
> @GeneratedValue(strategy = GenerationType.IDENTITY)
> private Long id;
> private String lastName;
> private String uppercaseLastName;
>
> public Long getId() {
> return id;
> }
>
> public String getLastName() {
> return lastName;
> }
>
> public void setLastName(String lastName) {
> this.lastName = lastName;
> }
>
> @PrePersist
> @PreUpdate
> public void prePersist() {
> if (lastName != null) {
> uppercaseLastName = lastName.toUpperCase();
> } else {
> uppercaseLastName = null;
> }
> }
>
> }
>
> public List<Person> getPeopleByLastName(String lastName) {
> Query q = em.createQuery("select from Person where uppercaseLastName
> = :p");
> q.setParameter("p", lastName.toUpperCase());
> return (List<Person>) q.getResultList();
>
> }
>
> JDO:
> import javax.jdo.listener.StoreCallback;
>
> @PersistenceCapable(identityType = IdentityType.APPLICATION)
> public class Person implements StoreCallback {
> @PrimaryKey
> @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
> private Long id;
> private String lastName;
> private String uppercaseLastName;
>
> public Long getId() {
> return id;
> }
>
> public String getLastName() {
> return lastName;
> }
>
> public void setLastName(String lastName) {
> this.lastName = lastName;
> }
>
> public void jdoPreStore() {
> if (lastName != null) {
> uppercaseLastName = lastName.toUpperCase();
> } else {
> uppercaseLastName = null;
> }
> }
>
> }
>
> public List<Person> getPeopleByLastName(String lastName) {
> Query q = pm.newQuery(Person.class, "uppercaseLastName == :p");
> return (List<Person>) q.execute(lastName.toUpperCase());
>
> }
>
> On 21 mar, 17:41, vchalmel <groupeprojeten...@gmail.com> wrote:
>
> > Hi !
>
> > I wonder how to compare a String stored in a datastore entity (field
> > "login") to an entry (also named login) considering their lowercase
> > version :
> > - I tried : "SELECT count(this) FROM "+Gestionnaire.class.getName()+"
> > WHERE LowerCase(login)== LowerCase('"+login+"')" which throws an
> > exception
>
> > I have another problem with this query, I don't want to exclude the
> > one-character login like, maybe "1", but this also fires an exception
> > ( java.lang.Character cannot be cast to
> > com.google.appengine.api.datastore.Key )
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