4 Querying and Persistence Options - Reference Documentation
Authors: Paras Lakhani
Version: 5.0.8.RELEASE
Table of Contents
4 Querying and Persistence Options
The GORM for Cassandra plugin supports passing various options to Cassandra when querying or persisting.4.1 Querying Options
Limiting results
Using themax parameter, you can specify that the query return a limited number of rows. Example:
def people = Person.list(max:2)
offset parameter, so you cannot page results this way.Fetch Size
Setting the fetch size, or number of rows returned simultaneously by a select query, is typically needed when queries return extremely large numbers of rows. To do this you can use thefetchSize argument:def people = Person.list([fetchSize: 200])
people = Person.findAllByFirstName("Barney", [fetchSize: 200])fetchSize to Integer.MAX_VALUE. Example:People.createCriteria().list {
'in' "lastName", ["Flintstone", "Rubble"]
order "name"
fetchSize Integer.MAX_VALUE
}Allow filtering
When you attempt a potentially expensive query Cassandra may throw an exception mentioning ALLOW FILTERING. To run the query, you can use theallowFiltering argument which is passed onto Cassandra. Imposing a limit using the max parameter is recommended to reduce memory used.Example:
def people = Person.findAllByFirstNameAndAgeLessThanEquals('Barney', 35, [allowFiltering:true, max:5])
def person = Person.findOrSaveWhere(firstName: 'Rubble', age: 35, [allowFiltering:true, flush:true])
def criteria = Person.createCriteria()
people = criteria.list (allowFiltering:true, max:5) {
and {
eq('firstName', 'Fred')
eq('age', 40)
}
}
people = criteria.list {
projections {
eq('firstName', 'Bob')
between("age", 40, 43)
}
allowFiltering true
max 5
}