/**
* Makes a quick request to the aggregation manager to see whether the cell value required by a
* particular cell request is in external cache.
*
* <p>'Quick' is relative. It is an asynchronous request (due to the aggregation manager being an
* actor) and therefore somewhat slow. If the segment is in cache, will save batching up future
* requests and re-executing the query. Win should be particularly noticeable for queries running
* on a populated cache. Without this feature, every query would require at least two iterations.
*
* <p>Request does not issue SQL to populate the segment. Nor does it try to find existing
* segments for rollup. Those operations can wait until next phase.
*
* <p>Client is responsible for adding the segment to its private cache.
*
* @param request Cell request
* @return Segment with data, or null if not in cache
*/
public SegmentWithData peek(final CellRequest request) {
final SegmentCacheManager.PeekResponse response =
execute(new PeekCommand(request, Locus.peek()));
for (SegmentHeader header : response.headerMap.keySet()) {
final SegmentBody body = compositeCache.get(header);
if (body != null) {
final SegmentBuilder.SegmentConverter converter =
response.converterMap.get(SegmentCacheIndexImpl.makeConverterKey(header));
if (converter != null) {
return converter.convert(header, body);
}
}
}
for (Map.Entry<SegmentHeader, Future<SegmentBody>> entry : response.headerMap.entrySet()) {
final Future<SegmentBody> bodyFuture = entry.getValue();
if (bodyFuture != null) {
final SegmentBody body = Util.safeGet(bodyFuture, "Waiting for segment to load");
final SegmentHeader header = entry.getKey();
final SegmentBuilder.SegmentConverter converter =
response.converterMap.get(SegmentCacheIndexImpl.makeConverterKey(header));
if (converter != null) {
return converter.convert(header, body);
}
}
}
return null;
}
public PeekResponse call() {
final RolapStar.Measure measure = request.getMeasure();
final RolapStar star = measure.getStar();
final RolapSchema schema = star.getSchema();
final AggregationKey key = new AggregationKey(request);
final List<SegmentHeader> headers =
indexRegistry
.getIndex(star)
.locate(
schema.getName(),
schema.getChecksum(),
measure.getCubeName(),
measure.getName(),
star.getFactTable().getAlias(),
request.getConstrainedColumnsBitKey(),
request.getMappedCellValues(),
AggregationKey.getCompoundPredicateStringList(
star, key.getCompoundPredicateList()));
final Map<SegmentHeader, Future<SegmentBody>> headerMap =
new HashMap<SegmentHeader, Future<SegmentBody>>();
final Map<List, SegmentBuilder.SegmentConverter> converterMap =
new HashMap<List, SegmentBuilder.SegmentConverter>();
// Is there a pending segment? (A segment that has been created and
// is loading via SQL.)
for (final SegmentHeader header : headers) {
final Future<SegmentBody> bodyFuture = indexRegistry.getIndex(star).getFuture(header);
if (bodyFuture != null) {
// Check if the DataSourceChangeListener wants us to clear
// the current segment
if (star.getChangeListener() != null
&& star.getChangeListener().isAggregationChanged(key)) {
/*
* We can't satisfy this request, and we must clear the
* data from our cache. We clear it from the index
* first, then queue up a job in the background
* to remove the data from all the caches.
*/
indexRegistry.getIndex(star).remove(header);
Util.safeGet(
cacheExecutor.submit(
new Runnable() {
public void run() {
try {
compositeCache.remove(header);
} catch (Throwable e) {
LOGGER.warn("remove header failed: " + header, e);
}
}
}),
"SegmentCacheManager.peek");
}
converterMap.put(
SegmentCacheIndexImpl.makeConverterKey(header), getConverter(star, header));
headerMap.put(header, bodyFuture);
}
}
return new PeekResponse(headerMap, converterMap);
}