maxwellguo created CASSANDRA-15796:
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Summary: Cassandra get range slice got Inaccurate estimates for
concurrencyFactor
Key: CASSANDRA-15796
URL: https://issues.apache.org/jira/browse/CASSANDRA-15796
Project: Cassandra
Issue Type: Bug
Components: Legacy/Coordination
Reporter: maxwellguo
Cassandra version :3.11.4
For table that do not got a regular column , when we do partition range read
and we got to the code function :
{code:java}
// Some comments here
public String getRangeSlice(PartitionRangeReadCommand command, ConsistencyLevel
consistencyLevel, long queryStartNanoTime)
{code}
we will do some calculation to estimate the data per range in the function :
{code:java}
// Some comments here
private static float estimateResultsPerRange(PartitionRangeReadCommand command,
Keyspace keyspace)
{code}
when we got no index so we will use :
{code:java}
// Some comments here
command.limits().estimateTotalResults(cfs)
--->(for CQLlimits)
*public float estimateTotalResults(ColumnFamilyStore cfs)
{
// TODO: we should start storing stats on the number of rows
(instead of the number of cells, which
// is what getMeanColumns returns)
float rowsPerPartition = ((float) cfs.getMeanColumns()) /
cfs.metadata.partitionColumns().regulars.size();
return rowsPerPartition * (cfs.estimateKeys());
}*
{code}
when the regulars is zero ,we will got an error result that is non-zero value
divided by zero .
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