EmfIndex Comparison

This page is intended to compare the two index implementations form different viewpoints such as

• Performance
• Memory Consumption
• How to build a convinient Query API on top of the low level API
  

Performance

Indexing

Indexing time

This test measured the time which is needed to index x-times the content of Ecore.ecore. (Containing 393 instances of EObject and 520 references)

1000 2000 3000 SAP 15,4 s 29,9 s 45,3 s Itemis 14,6 s 28,4 s 43,5 s

Memory consumption

This test measured the in memory size of the index. In the SAP case, paging was disabled

1000 2000 3000 SAP 136 million bytes 278 million bytes 408 million bytes Itemis 169 million bytes 340 million bytes 508 million bytes

Query response time

Query All EObject and all EReferences

1000 2000 3000 SAP 0,3 s 0,45 s 0,65 s Itemis 1,4 s 2,2 s 3,3 s

Query all references targeting a certain resource

1 2 4 8 16 32 64 128 SAP 0,6 ms 0,6 ms 0,6 ms 0,6 ms 0,6 ms 0,6 ms 0,6 ms 0,6 ms Itemis 5 ms 537 ms 3178 ms 15190 ms 65177 ms 268899 ms 1087066 ms

Query all instances of "EClass"

128 256 512 1024 2048 SAP 0,4 ms 0,8 ms 1,2 ms 4 ms 8,2 ms Itemis 72 ms 142 ms 287 ms 500 ms 1103 ms

Navigation Query required for convenient API

eObject.getResourceDescriptor() 7 µs resource.getEObjects() 104 µs resource.getReferences() 220 µs reference.getTargetObject() 12 µs

Convenient query API

The following proposal can be implemented on top of the low level API to provide a more convenient query API as proposed by Itemis. The basic idea would be to provide a specialized query factory for the convenient queries, which returns wrappers around the low level query objects. The query wrapper would also return a wrapped QueryResult object which in turn wraps the low level descriptors. The following snippet shows an example of the query factory.

public class ConvenientIndexQueryFactory {
 
	public ConvenientEObjectQuery<?> createEObjectQuery() {
		...
	}
 
	public ConvenientEReferenceQuery<?> createEReferenceQuery() {
		...
	}
 
	public ConvenientResourceQuery<ConvenientResourceDescriptor> createResourceQuery() {
		return new ConvenientResourceQueryImpl<ConvenientResourceDescriptor>();
	}

The returned resource query needs to subclass our ResourceQueryImpl class and override the createQueryResult() method. This method gets an iterable with low level descriptors. The QueryResult only implements the Iterable interface and has no further methods.

public class ConvenientResourceQueryImpl<T> extends ResourceQueryImpl<T> implements ConvenientResourceQuery<T> {
 
	@Override
	public QueryResult<T> createQueryResult(QueryExecutorInternal queryExecutor, Iterable<ResourceDescriptor> result) {
		return ...; // new QueryResult implementation
	}
 
}

A convenient user may use this API as like as the low level API:

public class ConvenientUser {
 
	public void test() {
		final ConvenientResourceQuery<ConvenientResourceDescriptor> query = new ConvenientIndexQueryFactory().createResourceQuery();
		query.uri("hallo");
 
		Index index = ...;
		index.executeQueryCommand(new QueryCommand() {
 
			@Override
			public void execute(QueryExecutor queryExecutor) {
				QueryResult<ConvenientResourceDescriptor> execute = queryExecutor.execute(query);
			}
 
		});
	}
}