org.apache.hadoop.hive.ql.optimizer.ConstantPropagate Maven / Gradle / Ivy
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*
* http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.hadoop.hive.ql.optimizer;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.ql.exec.FileSinkOperator;
import org.apache.hadoop.hive.ql.exec.FilterOperator;
import org.apache.hadoop.hive.ql.exec.GroupByOperator;
import org.apache.hadoop.hive.ql.exec.JoinOperator;
import org.apache.hadoop.hive.ql.exec.Operator;
import org.apache.hadoop.hive.ql.exec.ReduceSinkOperator;
import org.apache.hadoop.hive.ql.exec.ScriptOperator;
import org.apache.hadoop.hive.ql.exec.SelectOperator;
import org.apache.hadoop.hive.ql.exec.TableScanOperator;
import org.apache.hadoop.hive.ql.lib.DefaultGraphWalker;
import org.apache.hadoop.hive.ql.lib.DefaultRuleDispatcher;
import org.apache.hadoop.hive.ql.lib.Dispatcher;
import org.apache.hadoop.hive.ql.lib.GraphWalker;
import org.apache.hadoop.hive.ql.lib.Node;
import org.apache.hadoop.hive.ql.lib.NodeProcessor;
import org.apache.hadoop.hive.ql.lib.Rule;
import org.apache.hadoop.hive.ql.lib.RuleRegExp;
import org.apache.hadoop.hive.ql.parse.ParseContext;
import org.apache.hadoop.hive.ql.parse.SemanticException;
/**
* Implementation of one of the rule-based optimization steps. ConstantPropagate traverse the DAG
* from root to child. For each conditional expression, process as follows:
*
* 1. Fold constant expression: if the expression is a UDF and all parameters are constant.
*
* 2. Shortcut expression: if the expression is a logical operator and it can be shortcut by
* some constants of its parameters.
*
* 3. Propagate expression: if the expression is an assignment like column=constant, the expression
* will be propagate to parents to see if further folding operation is possible.
*/
public class ConstantPropagate implements Transform {
private static final Log LOG = LogFactory.getLog(ConstantPropagate.class);
protected ParseContext pGraphContext;
public ConstantPropagate() {}
/**
* Transform the query tree.
*
* @param pactx
* the current parse context
*/
@Override
public ParseContext transform(ParseContext pactx) throws SemanticException {
pGraphContext = pactx;
// generate pruned column list for all relevant operators
ConstantPropagateProcCtx cppCtx = new ConstantPropagateProcCtx();
// create a walker which walks the tree in a DFS manner while maintaining
// the operator stack. The dispatcher
// generates the plan from the operator tree
Map opRules = new LinkedHashMap();
opRules.put(new RuleRegExp("R1", FilterOperator.getOperatorName() + "%"),
ConstantPropagateProcFactory.getFilterProc());
opRules.put(new RuleRegExp("R2", GroupByOperator.getOperatorName() + "%"),
ConstantPropagateProcFactory.getGroupByProc());
opRules.put(new RuleRegExp("R3", SelectOperator.getOperatorName() + "%"),
ConstantPropagateProcFactory.getSelectProc());
opRules.put(new RuleRegExp("R4", FileSinkOperator.getOperatorName() + "%"),
ConstantPropagateProcFactory.getFileSinkProc());
opRules.put(new RuleRegExp("R5", ReduceSinkOperator.getOperatorName() + "%"),
ConstantPropagateProcFactory.getReduceSinkProc());
opRules.put(new RuleRegExp("R6", JoinOperator.getOperatorName() + "%"),
ConstantPropagateProcFactory.getJoinProc());
opRules.put(new RuleRegExp("R7", TableScanOperator.getOperatorName() + "%"),
ConstantPropagateProcFactory.getTableScanProc());
opRules.put(new RuleRegExp("R8", ScriptOperator.getOperatorName() + "%"),
ConstantPropagateProcFactory.getStopProc());
// The dispatcher fires the processor corresponding to the closest matching
// rule and passes the context along
Dispatcher disp = new DefaultRuleDispatcher(ConstantPropagateProcFactory
.getDefaultProc(), opRules, cppCtx);
GraphWalker ogw = new ConstantPropagateWalker(disp);
// Create a list of operator nodes to start the walking.
ArrayList topNodes = new ArrayList();
topNodes.addAll(pGraphContext.getTopOps().values());
ogw.startWalking(topNodes, null);
for (Operator opToDelete : cppCtx.getOpToDelete()) {
if (opToDelete.getParentOperators() == null || opToDelete.getParentOperators().size() != 1) {
throw new RuntimeException("Error pruning operator " + opToDelete
+ ". It should have only 1 parent.");
}
opToDelete.getParentOperators().get(0).removeChildAndAdoptItsChildren(opToDelete);
}
return pGraphContext;
}
/**
* Walks the op tree in root first order.
*/
public static class ConstantPropagateWalker extends DefaultGraphWalker {
public ConstantPropagateWalker(Dispatcher disp) {
super(disp);
}
@Override
public void walk(Node nd) throws SemanticException {
List parents = ((Operator) nd).getParentOperators();
if ((parents == null)
|| getDispatchedList().containsAll(parents)) {
opStack.push(nd);
// all children are done or no need to walk the children
dispatch(nd, opStack);
opStack.pop();
} else {
getToWalk().removeAll(parents);
getToWalk().add(0, nd);
getToWalk().addAll(0, parents);
return;
}
// move all the children to the front of queue
List children = nd.getChildren();
if (children != null) {
getToWalk().removeAll(children);
getToWalk().addAll(children);
}
}
}
}