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column_family: Return proper cardinality for toppartitions requests 

Right now, in the finishLocalSampling method of the ColumnFamilyStore
we return the size of the list of returned partitions. Instead, we should
be propagating the actual cardinality of the sampled set.
Let's just read the read_cardinality and write_cardinality properties
of the scylla's REST API response.

Fixes #148
This commit is contained in:
Piotr Wojtczak 2020-12-11 16:17:57 +01:00 committed by Avi Kivity
parent 6174a47924
commit 20469bf749
1 changed files with 3 additions and 1 deletions
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4
src/main/java/org/apache/cassandra/db/ColumnFamilyStore.java
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@ -29,6 +29,7 @@ import static java.util.stream.Collectors.toMap;
import static javax.json.Json.createObjectBuilder;
import java.io.StringReader;
import java.io.OutputStream;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashMap;
@ -545,6 +546,7 @@ public class ColumnFamilyStore extends MetricsMBean implements ColumnFamilyStore
TabularDataSupport result = new TabularDataSupport(COUNTER_TYPE);
JsonArray counters = tableSamplerResult.getJsonArray((samplerType.equalsIgnoreCase("reads")) ? "read" : "write");
long cardinality = tableSamplerResult.getJsonNumber((samplerType.equalsIgnoreCase("reads")) ? "read_cardinality" : "write_cardinality").longValue();
long size = 0;
if (counters != null) {
size = (count > counters.size()) ? counters.size() : count;
@ -558,6 +560,6 @@ public class ColumnFamilyStore extends MetricsMBean implements ColumnFamilyStore
}
}
//FIXME: size is not the cardinality, a true value needs to be propogated
return new CompositeDataSupport(SAMPLING_RESULT, SAMPLER_NAMES, new Object[] { size, result });
return new CompositeDataSupport(SAMPLING_RESULT, SAMPLER_NAMES, new Object[] { cardinality, result });
}
}