org.apache.hadoop.hive.ql.optimizer.ppr.ExprProcFactory Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
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package org.apache.hadoop.hive.ql.optimizer.ppr;
import java.util.Map;
import org.apache.hadoop.hive.ql.lib.Node;
import org.apache.hadoop.hive.ql.lib.NodeProcessor;
import org.apache.hadoop.hive.ql.lib.NodeProcessorCtx;
import org.apache.hadoop.hive.ql.optimizer.PrunerExpressionOperatorFactory;
import org.apache.hadoop.hive.ql.optimizer.PrunerUtils;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.plan.ExprNodeColumnDesc;
import org.apache.hadoop.hive.ql.plan.ExprNodeConstantDesc;
import org.apache.hadoop.hive.ql.plan.ExprNodeDesc;
/**
* Expression processor factory for partition pruning. Each processor tries to
* convert the expression subtree into a partition pruning expression. This
* expression is then used to figure out whether a particular partition should
* be scanned or not.
*
* * Refactor:
* Move main logic to PrunerExpressionOperatorFactory. ExprProcFactory extends it to reuse logic.
*
* Any other pruner can reuse it by creating a class extending from PrunerExpressionOperatorFactory.
*
* Only specific logic is in genPruner(..) which is in its own class like ExprProcFactory.
*
*/
public final class ExprProcFactory extends PrunerExpressionOperatorFactory {
private ExprProcFactory() {
// prevent instantiation
}
/**
* Processor for ppr column expressions.
*/
public static class PPRColumnExprProcessor extends ColumnExprProcessor {
@Override
protected ExprNodeDesc processColumnDesc(NodeProcessorCtx procCtx, ExprNodeColumnDesc cd) {
ExprNodeDesc newcd;
ExprProcCtx epc = (ExprProcCtx) procCtx;
if (cd.getTabAlias().equalsIgnoreCase(epc.getTabAlias())
&& cd.getIsPartitionColOrVirtualCol()) {
newcd = cd.clone();
} else {
newcd = new ExprNodeConstantDesc(cd.getTypeInfo(), null);
}
return newcd;
}
}
/**
* Instantiate column processor.
*
* @return
*/
public static NodeProcessor getColumnProcessor() {
return new PPRColumnExprProcessor();
}
/**
* Generates the partition pruner for the expression tree.
*
* @param tabAlias
* The table alias of the partition table that is being considered
* for pruning
* @param pred
* The predicate from which the partition pruner needs to be
* generated
* @return The pruner expression.
*/
public static ExprNodeDesc genPruner(
String tabAlias, ExprNodeDesc pred) throws SemanticException {
// Create the walker, the rules dispatcher and the context.
ExprProcCtx pprCtx = new ExprProcCtx(tabAlias);
/* Move common logic to PrunerUtils.walkExprTree(...) so that it can be reused. */
Map outputMap = PrunerUtils.walkExprTree(pred, pprCtx, getColumnProcessor(),
getFieldProcessor(), getGenericFuncProcessor(), getDefaultExprProcessor());
// Get the exprNodeDesc corresponding to the first start node;
return (ExprNodeDesc) outputMap.get(pred);
}
}