Taste of SQL for In-Memory Cache Queries
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Join For FreeI plan to blog in more detail about support of native SQL in GridGain
data grid in a few days, but here is just a taste on how complex of an
SQL statement you can execute against GridGain distributed in-memory
cache. Note that you are not querying a database - you are querying
objects cached in memory.
The query below utilizes H2 database
SQL over JDBC syntax to query a collection of QueueItems at specified
positions of a dynamic priority-based queue stored in distributed
GridGain cache. As we know, querying an element at a certain position of
a result set is not trivial in any SQL, and nested 'select' statements with 'rownum'
field usually need to be used. On top of that we need to pass a
collection of item positions to a query, which is also a fairly advanced
feature.
String sql =
"select * from (" +
"select *, rownum as r from (" +
"select * from QueueItem where qid=? " +
"order by priority desc, seq asc" +
")" +
") where r in (select * from table(x int=?))"
GridCacheQuery itemsQry = cache.createQuery(SQL, QueueItem.class, sql);
// Specify positions of queue items we want to get.
Collection<Integer> positions = Collections.asList(10, 12, 14);
// Query items at specified positions from queue with ID 123.
GridCacheQueryFuture fut = itemsQry.queryArguments(123, positions).execute();
System.out.println("Queried queue items at specified positions: " + fut.get());
Pretty powerful in my view especially when you also get smart routing, pagination, custom transformers, reducers, visit-only support, text queries, and a lot more...
More information on GridGain queries can be found here or here.
From http://gridgain.blogspot.com/2011/01/taste-of-sql-for-in-memory-cache.html
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