/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hive.ql.optimizer;
import java.io.Serializable;
import java.util.Map;
import java.util.Stack;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hive.ql.Context;
import org.apache.hadoop.hive.ql.exec.Operator;
import org.apache.hadoop.hive.ql.exec.TableScanOperator;
import org.apache.hadoop.hive.ql.exec.Task;
import org.apache.hadoop.hive.ql.exec.TaskFactory;
import org.apache.hadoop.hive.ql.exec.UnionOperator;
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.GenMRProcContext.GenMRUnionCtx;
import org.apache.hadoop.hive.ql.optimizer.GenMRProcContext.GenMapRedCtx;
import org.apache.hadoop.hive.ql.optimizer.unionproc.UnionProcContext;
import org.apache.hadoop.hive.ql.optimizer.unionproc.UnionProcContext.UnionParseContext;
import org.apache.hadoop.hive.ql.optimizer.unionproc.UnionProcFactory;
import org.apache.hadoop.hive.ql.parse.ParseContext;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.plan.MapredWork;
import org.apache.hadoop.hive.ql.plan.OperatorDesc;
import org.apache.hadoop.hive.ql.plan.PlanUtils;
import org.apache.hadoop.hive.ql.plan.TableDesc;
/**
* Processor for the rule - TableScan followed by Union.
*/
public class GenMRUnion1 implements NodeProcessor {
public GenMRUnion1() {
}
/**
* Process the union if all sub-queries are map-only
*
* @return
* @throws SemanticException
*/
private Object processMapOnlyUnion(UnionOperator union, Stack<Node> stack,
GenMRProcContext ctx, UnionProcContext uCtx) throws SemanticException {
// merge currTask from multiple topOps
GenMRUnionCtx uCtxTask = ctx.getUnionTask(union);
if (uCtxTask != null) {
// get task associated with this union
Task<? extends Serializable> uTask = ctx.getUnionTask(union).getUTask();
if (uTask != null) {
if (ctx.getCurrTask() != null && ctx.getCurrTask() != uTask) {
// if ctx.getCurrTask() is in rootTasks, should be removed
ctx.getRootTasks().remove(ctx.getCurrTask());
}
ctx.setCurrTask(uTask);
}
}
UnionParseContext uPrsCtx = uCtx.getUnionParseContext(union);
ctx.getMapCurrCtx().put(
union,
new GenMapRedCtx(ctx.getCurrTask(),
ctx.getCurrAliasId()));
// if the union is the first time seen, set current task to GenMRUnionCtx
uCtxTask = ctx.getUnionTask(union);
if (uCtxTask == null) {
uCtxTask = new GenMRUnionCtx(ctx.getCurrTask());
ctx.setUnionTask(union, uCtxTask);
}
Task<? extends Serializable> uTask = ctx.getCurrTask();
if (uTask.getParentTasks() == null
|| uTask.getParentTasks().isEmpty()) {
if (!ctx.getRootTasks().contains(uTask)) {
ctx.getRootTasks().add(uTask);
}
}
return true;
}
/**
* Process the union when the parent is a map-reduce job. Create a temporary
* output, and let the union task read from the temporary output.
*
* The files created for all the inputs are in the union context and later
* used to initialize the union plan
*
* @param parent
* @param child
* @param uTask
* @param ctx
* @param uCtxTask
*/
private void processSubQueryUnionCreateIntermediate(
Operator<? extends OperatorDesc> parent,
Operator<? extends OperatorDesc> child,
Task<? extends Serializable> uTask, GenMRProcContext ctx,
GenMRUnionCtx uCtxTask) {
ParseContext parseCtx = ctx.getParseCtx();
TableDesc tt_desc = PlanUtils.getIntermediateFileTableDesc(PlanUtils
.getFieldSchemasFromRowSchema(
parent.getSchema(), "temporarycol"));
// generate the temporary file
Context baseCtx = parseCtx.getContext();
Path taskTmpDir = baseCtx.getMRTmpPath();
// Create the temporary file, its corresponding FileSinkOperaotr, and
// its corresponding TableScanOperator.
TableScanOperator tableScanOp =
GenMapRedUtils.createTemporaryFile(parent, child, taskTmpDir, tt_desc, parseCtx);
// Add the path to alias mapping
uCtxTask.addTaskTmpDir(taskTmpDir.toUri().toString());
uCtxTask.addTTDesc(tt_desc);
uCtxTask.addListTopOperators(tableScanOp);
// The union task is empty. The files created for all the inputs are
// assembled in the union context and later used to initialize the union
// plan
Task<? extends Serializable> currTask = ctx.getCurrTask();
currTask.addDependentTask(uTask);
if (ctx.getRootTasks().contains(uTask)) {
ctx.getRootTasks().remove(uTask);
if (!ctx.getRootTasks().contains(currTask) &&
shouldBeRootTask(currTask)) {
ctx.getRootTasks().add(currTask);
}
}
}
/**
* Union Operator encountered. A map-only query is encountered at the given
* position. However, at least one sub-query is a map-reduce job. Copy the
* information from the current top operator to the union context.
*
* @param ctx
* @param uCtxTask
* @param union
* @param stack
* @throws SemanticException
*/
private void processSubQueryUnionMerge(GenMRProcContext ctx,
GenMRUnionCtx uCtxTask, UnionOperator union, Stack<Node> stack)
throws SemanticException {
// The current plan can be thrown away after being merged with the union
// plan
Task<? extends Serializable> uTask = uCtxTask.getUTask();
ctx.setCurrTask(uTask);
TableScanOperator topOp = ctx.getCurrTopOp();
if (topOp != null && !ctx.isSeenOp(uTask, topOp)) {
GenMapRedUtils.setTaskPlan(ctx.getCurrAliasId(), ctx
.getCurrTopOp(), uTask, false, ctx);
}
}
/**
* Union Operator encountered . Currently, the algorithm is pretty simple: If
* all the sub-queries are map-only, don't do anything. Otherwise, insert a
* FileSink on top of all the sub-queries.
*
* This can be optimized later on.
*
* @param nd
* the file sink operator encountered
* @param opProcCtx
* context
*/
@Override
public Object process(Node nd, Stack<Node> stack, NodeProcessorCtx opProcCtx,
Object... nodeOutputs) throws SemanticException {
UnionOperator union = (UnionOperator) nd;
GenMRProcContext ctx = (GenMRProcContext) opProcCtx;
ParseContext parseCtx = ctx.getParseCtx();
UnionProcContext uCtx = parseCtx.getUCtx();
// Map-only subqueries can be optimized in future to not write to a file in
// future
Map<Operator<? extends OperatorDesc>, GenMapRedCtx> mapCurrCtx = ctx.getMapCurrCtx();
if (union.getConf().isAllInputsInSameReducer()) {
// All inputs of this UnionOperator are in the same Reducer.
// We do not need to break the operator tree.
mapCurrCtx.put((Operator<? extends OperatorDesc>) nd,
new GenMapRedCtx(ctx.getCurrTask(),ctx.getCurrAliasId()));
return null;
}
UnionParseContext uPrsCtx = uCtx.getUnionParseContext(union);
ctx.setCurrUnionOp(union);
// The plan needs to be broken only if one of the sub-queries involve a
// map-reduce job
if (uPrsCtx.allMapOnlySubQ()) {
return processMapOnlyUnion(union, stack, ctx, uCtx);
}
assert uPrsCtx != null;
Task<? extends Serializable> currTask = ctx.getCurrTask();
int pos = UnionProcFactory.getPositionParent(union, stack);
Task<? extends Serializable> uTask = null;
MapredWork uPlan = null;
// union is encountered for the first time
GenMRUnionCtx uCtxTask = ctx.getUnionTask(union);
if (uCtxTask == null) {
uPlan = GenMapRedUtils.getMapRedWork(parseCtx);
uTask = TaskFactory.get(uPlan, parseCtx.getConf());
uCtxTask = new GenMRUnionCtx(uTask);
ctx.setUnionTask(union, uCtxTask);
}
else {
uTask = uCtxTask.getUTask();
}
// Copy into the current union task plan if
if (uPrsCtx.getMapOnlySubq(pos) && uPrsCtx.getRootTask(pos)) {
processSubQueryUnionMerge(ctx, uCtxTask, union, stack);
if (ctx.getRootTasks().contains(currTask)) {
ctx.getRootTasks().remove(currTask);
}
}
// If it a map-reduce job, create a temporary file
else {
// is the current task a root task
if (shouldBeRootTask(currTask)
&& !ctx.getRootTasks().contains(currTask)
&& (currTask.getParentTasks() == null
|| currTask.getParentTasks().isEmpty())) {
ctx.getRootTasks().add(currTask);
}
processSubQueryUnionCreateIntermediate(union.getParentOperators().get(pos), union, uTask,
ctx, uCtxTask);
// the currAliasId and CurrTopOp is not valid any more
ctx.setCurrAliasId(null);
ctx.setCurrTopOp(null);
ctx.getOpTaskMap().put(null, uTask);
}
ctx.setCurrTask(uTask);
mapCurrCtx.put((Operator<? extends OperatorDesc>) nd,
new GenMapRedCtx(ctx.getCurrTask(), null));
return true;
}
private boolean shouldBeRootTask(
Task<? extends Serializable> currTask) {
return currTask.getParentTasks() == null
|| (currTask.getParentTasks().size() == 0);
}
}