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java.lang.Object org.apache.hadoop.hive.ql.optimizer.stats.annotation.StatsRulesProcFactory.DefaultStatsRule org.apache.hadoop.hive.ql.optimizer.stats.annotation.StatsRulesProcFactory.FilterStatsRule
public static class StatsRulesProcFactory.FilterStatsRule
FILTER operator does not change the average row size but it does change the number of rows emitted. The reduction in the number of rows emitted is dependent on the filter expression.
- Alternate formula T(S) = T(R) (V(R,A) - 1) / V(R,A)
- Alternate formula T(S) = T(R) * ( 1 - ( 1 - m1/T(R) ) * ( 1 - m2/T(R) ))
where, m1 is the number of tuples that satisfy condition1 and m2 is the number of tuples that satisfy condition2
Worst case: If no column statistics are available, then evaluation of predicate expression will assume worst case (i.e; half the input rows) for each of predicate expression.
For more information, refer 'Estimating The Cost Of Operations' chapter in "Database Systems: The Complete Book" by Garcia-Molina et. al.
Constructor Summary | |
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StatsRulesProcFactory.FilterStatsRule()
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Method Summary | |
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Object |
process(Node nd,
Stack<Node> stack,
NodeProcessorCtx procCtx,
Object... nodeOutputs)
Generic process for all ops that don't have specific implementations. |
Methods inherited from class java.lang.Object |
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equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public StatsRulesProcFactory.FilterStatsRule()
Method Detail |
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public Object process(Node nd, Stack<Node> stack, NodeProcessorCtx procCtx, Object... nodeOutputs) throws SemanticException
NodeProcessor
process
in interface NodeProcessor
process
in class StatsRulesProcFactory.DefaultStatsRule
nd
- operator to processprocCtx
- operator processor contextnodeOutputs
- A variable argument list of outputs from other nodes in the walk
SemanticException
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