BigMemory Go 4.3.5 | Product Documentation | BigMemory Go Developer Guide | Searching a Cache | Creating a Query
 
Creating a Query
BigMemory Go uses a fluent, object-oriented query API, following the principles of a Domain-Specific Language (DSL), which should be familiar to Java programmers. For example:
Query query = cache.createQuery().addCriteria(age.eq(35)).includeKeys().end();
Results results = query.execute();
Using Attributes in Queries
If declared and available, the well-known attributes are referenced by their names or the convenience attributes are used directly:
Results results = cache.createQuery().addCriteria(Query.KEY.eq(35)).execute();
Results results = cache.createQuery().addCriteria(Query.VALUE.lt(10)).execute();
Other attributes are referenced by the names in the configuration:
Attribute<Integer> age = cache.getSearchAttribute("age");
Attribute<String> gender = cache.getSearchAttribute("gender");
Attribute<String> name = cache.getSearchAttribute("name");
Expressions
A Query is built up using Expressions. Expressions can include logical operators such as <and> and <or>, and comparison operators such as <ge> (>=), <between>, and <like>. The configuration, addCriteria(...), is used to add a clause to a query. Adding a further clause automatically "<and>s" the clauses.
query = cache.createQuery().includeKeys()
.addCriteria(age.le(65))
.add(gender.eq("male"))
.end();
Both logical and comparison operators implement the Criteria interface. To add a criterion with a different logical operator, explicitly nest it within a new logical operator Criteria object. For example, to check for age = 35 or gender = female:
query.addCriteria(new Or(age.eq(35),
gender.eq(Gender.FEMALE))
);
More complex compound expressions can be created through additional nesting. For a complete list of expressions, see the Expression Javadoc at http://www.ehcache.org/apidocs/2.10.1/net/sf/ehcache/search/expression/package-summary.html.
List of Operators
Operators are available as methods on attributes, so they are used by adding a ".". For example, "lt" means "less than" and is used as age.lt(10), which is a shorthand way of saying age LessThan(10).
Shorthand
Criteria Class
Description
and
And
The Boolean AND logical operator.
between
Between
A comparison operator meaning between two values.
eq
EqualTo
A comparison operator meaning Java "equals to" condition.
gt
GreaterThan
A comparison operator meaning greater than.
ge
GreaterThanOrEqual
A comparison operator meaning greater than or equal to.
in
InCollection
A comparison operator meaning in the collection given as an argument.
lt
LessThan
A comparison operator meaning less than.
le
LessThanOrEqual
A comparison operator meaning less than or equal to.
ilike
ILike
A regular expression matcher. "?" and "*" may be used. Note that placing a wildcard in front of the expression will cause a table scan. ILike is always case insensitive.
isNull
IsNull
Tests whether the value of an attribute with given name is null.
notNull
NotNull
Tests whether the value of an attribute with given name is NOT null.
not
Not
The Boolean NOT logical operator,
ne
NotEqualTo
A comparison operator meaning not the Java "equals to" condition,
or
Or
The Boolean OR logical operator.
For Strings, the operators are case-insensitive.
Making Queries Immutable
By default, a query can be executed, modified, and re-executed. If end( ) is called, the query is made immutable.

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