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Cum sa obtii mai mult de 1000 de entitati dintr-un query pe tabelele din Windows Azure

Pentru a putea obtine date din tabelele din Windows Azure putem sa folosim DataServiceQuery. Acesta suporta LINQ, astfel ne va fi foarte usor sa filtram continutul.
DataServiceQuery<Person> queryPersons =
.Where( p => p.Age >= 18 );
var result = queryPersons.Execute();
In variabila result o sa avem toate persoanele care au varsta mai mare sau egala cu 18.
Problema apare cand rezultatul contine mai mult de 1000 de entitati. Un query pe tabele din cloud va returna maxim 1000 de rezultate. In cazul in care acest numar este depasit acesta va contine doua token-uri pe baza carora se pot obtine si celelate entitati din query.
Cele doua token-uri reprezinta token-ul pentru Partition Key si Row Key. Se pot obtine din heather-ul rezultatului:
var resultQOR = (QueryOperationResponse)result;
string nextPartitionToken = null;
string nextRowToken = null;
resultQOR.Headers.TryGetValue("x-ms-continuation-NextPartitionKey", out nextPartitionToken);
resultQOR.Headers.TryGetValue("x-ms-continuation-NextRowKey", out nextRowToken);
Cele doua token-uri se pot trasmite mai departe la query pentru a obtine urmatorul set de rezultate.
queryPersons = queryPersons
.AddQueryOption("NextPartitionKey", nextPartitionToken)
.AddQueryOption("NextRowKey", nextRowToken);
var rezult2 = queryPersons.Execute();
In result2 am obtinut urmatoarele 1000 entitati din tabel.
Folosind acest mecanism putem sa implementam si un mecanism de paginare.


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