com.hazelcast.org.apache.calcite.rel.rules.CalcRelSplitter Maven / Gradle / Ivy
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* 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 com.hazelcast.org.apache.calcite.rel.rules;
import com.hazelcast.org.apache.calcite.plan.RelOptCluster;
import com.hazelcast.org.apache.calcite.plan.RelOptPlanner;
import com.hazelcast.org.apache.calcite.plan.RelTraitSet;
import com.hazelcast.org.apache.calcite.rel.RelNode;
import com.hazelcast.org.apache.calcite.rel.core.Calc;
import com.hazelcast.org.apache.calcite.rel.logical.LogicalCalc;
import com.hazelcast.org.apache.calcite.rel.type.RelDataType;
import com.hazelcast.org.apache.calcite.rel.type.RelDataTypeFactory;
import com.hazelcast.org.apache.calcite.rex.RexCall;
import com.hazelcast.org.apache.calcite.rex.RexDynamicParam;
import com.hazelcast.org.apache.calcite.rex.RexFieldAccess;
import com.hazelcast.org.apache.calcite.rex.RexInputRef;
import com.hazelcast.org.apache.calcite.rex.RexLiteral;
import com.hazelcast.org.apache.calcite.rex.RexLocalRef;
import com.hazelcast.org.apache.calcite.rex.RexNode;
import com.hazelcast.org.apache.calcite.rex.RexProgram;
import com.hazelcast.org.apache.calcite.rex.RexShuttle;
import com.hazelcast.org.apache.calcite.rex.RexUtil;
import com.hazelcast.org.apache.calcite.rex.RexVisitorImpl;
import com.hazelcast.org.apache.calcite.tools.RelBuilder;
import com.hazelcast.org.apache.calcite.util.Litmus;
import com.hazelcast.org.apache.calcite.util.Util;
import com.hazelcast.org.apache.calcite.util.graph.DefaultDirectedGraph;
import com.hazelcast.org.apache.calcite.util.graph.DefaultEdge;
import com.hazelcast.org.apache.calcite.util.graph.DirectedGraph;
import com.hazelcast.org.apache.calcite.util.graph.TopologicalOrderIterator;
import com.hazelcast.com.google.common.base.Preconditions;
import com.hazelcast.com.google.common.primitives.Ints;
import com.hazelcast.org.checkerframework.checker.nullness.qual.Nullable;
import com.hazelcast.org.slf4j.Logger;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Set;
/**
* CalcRelSplitter operates on a
* {@link com.hazelcast.org.apache.calcite.rel.core.Calc} with multiple {@link RexCall}
* sub-expressions that cannot all be implemented by a single concrete
* {@link RelNode}.
*
* For example, the Java and Fennel calculator do not implement an identical
* set of operators. The Calc can be used to split a single Calc with
* mixed Java- and Fennel-only operators into a tree of Calc object that can
* each be individually implemented by either Java or Fennel.and splits it into
* several Calc instances.
*
*
Currently the splitter is only capable of handling two "rel types". That
* is, it can deal with Java vs. Fennel Calcs, but not Java vs. Fennel vs.
* some other type of Calc.
*
*
See {@link ProjectToWindowRule}
* for an example of how this class is used.
*/
public abstract class CalcRelSplitter {
//~ Static fields/initializers ---------------------------------------------
private static final Logger RULE_LOGGER = RelOptPlanner.LOGGER;
//~ Instance fields --------------------------------------------------------
protected final RexProgram program;
private final RelDataTypeFactory typeFactory;
private final RelType[] relTypes;
private final RelOptCluster cluster;
private final RelTraitSet traits;
private final RelNode child;
protected final RelBuilder relBuilder;
//~ Constructors -----------------------------------------------------------
/**
* Constructs a CalcRelSplitter.
*
* @param calc Calc to split
* @param relTypes Array of rel types, e.g. {Java, Fennel}. Must be
* distinct.
*/
CalcRelSplitter(Calc calc, RelBuilder relBuilder, RelType[] relTypes) {
this.relBuilder = relBuilder;
for (int i = 0; i < relTypes.length; i++) {
assert relTypes[i] != null;
for (int j = 0; j < i; j++) {
assert relTypes[i] != relTypes[j]
: "Rel types must be distinct";
}
}
this.program = calc.getProgram();
this.cluster = calc.getCluster();
this.traits = calc.getTraitSet();
this.typeFactory = calc.getCluster().getTypeFactory();
this.child = calc.getInput();
this.relTypes = relTypes;
}
//~ Methods ----------------------------------------------------------------
RelNode execute() {
// Check that program is valid. In particular, this means that every
// expression is trivial (either an atom, or a function applied to
// references to atoms) and every expression depends only on
// expressions to the left.
assert program.isValid(Litmus.THROW, null);
final List exprList = program.getExprList();
final RexNode[] exprs = exprList.toArray(new RexNode[0]);
assert !RexUtil.containComplexExprs(exprList);
// Figure out what level each expression belongs to.
int[] exprLevels = new int[exprs.length];
// The type of a level is given by
// relTypes[levelTypeOrdinals[level]].
int[] levelTypeOrdinals = new int[exprs.length];
int levelCount = chooseLevels(exprs, -1, exprLevels, levelTypeOrdinals);
// For each expression, figure out which is the highest level where it
// is used.
int[] exprMaxUsingLevelOrdinals =
new HighestUsageFinder(exprs, exprLevels)
.getMaxUsingLevelOrdinals();
// If expressions are used as outputs, mark them as higher than that.
final List projectRefList = program.getProjectList();
final RexLocalRef conditionRef = program.getCondition();
for (RexLocalRef projectRef : projectRefList) {
exprMaxUsingLevelOrdinals[projectRef.getIndex()] = levelCount;
}
if (conditionRef != null) {
exprMaxUsingLevelOrdinals[conditionRef.getIndex()] = levelCount;
}
// Print out what we've got.
if (RULE_LOGGER.isTraceEnabled()) {
traceLevelExpressions(
exprs,
exprLevels,
levelTypeOrdinals,
levelCount);
}
// Now build the calcs.
RelNode rel = child;
final int inputFieldCount = program.getInputRowType().getFieldCount();
int[] inputExprOrdinals = identityArray(inputFieldCount);
boolean doneCondition = false;
for (int level = 0; level < levelCount; level++) {
final int[] projectExprOrdinals;
final RelDataType outputRowType;
if (level == (levelCount - 1)) {
outputRowType = program.getOutputRowType();
projectExprOrdinals = new int[projectRefList.size()];
for (int i = 0; i < projectExprOrdinals.length; i++) {
projectExprOrdinals[i] = projectRefList.get(i).getIndex();
}
} else {
outputRowType = null;
// Project the expressions which are computed at this level or
// before, and will be used at later levels.
List projectExprOrdinalList = new ArrayList<>();
for (int i = 0; i < exprs.length; i++) {
RexNode expr = exprs[i];
if (expr instanceof RexLiteral) {
// Don't project literals. They are always created in
// the level where they are used.
exprLevels[i] = -1;
continue;
}
if ((exprLevels[i] <= level)
&& (exprMaxUsingLevelOrdinals[i] > level)) {
projectExprOrdinalList.add(i);
}
}
projectExprOrdinals = Ints.toArray(projectExprOrdinalList);
}
final RelType relType = relTypes[levelTypeOrdinals[level]];
// Can we do the condition this level?
int conditionExprOrdinal = -1;
if ((conditionRef != null) && !doneCondition) {
conditionExprOrdinal = conditionRef.getIndex();
if ((exprLevels[conditionExprOrdinal] > level)
|| !relType.supportsCondition()) {
// stand down -- we're not ready to do the condition yet
conditionExprOrdinal = -1;
} else {
doneCondition = true;
}
}
RexProgram program1 =
createProgramForLevel(
level,
levelCount,
rel.getRowType(),
exprs,
exprLevels,
inputExprOrdinals,
projectExprOrdinals,
conditionExprOrdinal,
outputRowType);
rel =
relType.makeRel(cluster, traits, relBuilder, rel, program1);
// Sometimes a level's program merely projects its inputs. We don't
// want these. They cause an explosion in the search space.
if (rel instanceof LogicalCalc
&& ((LogicalCalc) rel).getProgram().isTrivial()) {
rel = rel.getInput(0);
}
rel = handle(rel);
// The outputs of this level will be the inputs to the next level.
inputExprOrdinals = projectExprOrdinals;
}
Preconditions.checkArgument(doneCondition || (conditionRef == null),
"unhandled condition");
return rel;
}
/**
* Opportunity to further refine the relational expression created for a
* given level. The default implementation returns the relational expression
* unchanged.
*/
protected RelNode handle(RelNode rel) {
return rel;
}
/**
* Figures out which expressions to calculate at which level.
*
* @param exprs Array of expressions
* @param conditionOrdinal Ordinal of the condition expression, or -1 if no
* condition
* @param exprLevels Level ordinal for each expression (output)
* @param levelTypeOrdinals The type of each level (output)
* @return Number of levels required
*/
private int chooseLevels(
final RexNode[] exprs,
int conditionOrdinal,
int[] exprLevels,
int[] levelTypeOrdinals) {
final int inputFieldCount = program.getInputRowType().getFieldCount();
int levelCount = 0;
final MaxInputFinder maxInputFinder = new MaxInputFinder(exprLevels);
boolean[] relTypesPossibleForTopLevel = new boolean[relTypes.length];
Arrays.fill(relTypesPossibleForTopLevel, true);
// Compute the order in which to visit expressions.
final List> cohorts = getCohorts();
final List permutation =
computeTopologicalOrdering(exprs, cohorts);
for (int i : permutation) {
RexNode expr = exprs[i];
final boolean condition = i == conditionOrdinal;
if (i < inputFieldCount) {
assert expr instanceof RexInputRef;
exprLevels[i] = -1;
continue;
}
// Deduce the minimum level of the expression. An expression must
// be at a level greater than or equal to all of its inputs.
int level = maxInputFinder.maxInputFor(expr);
// If the expression is in a cohort, it can occur no lower than the
// levels of other expressions in the same cohort.
Set cohort = findCohort(cohorts, i);
if (cohort != null) {
for (Integer exprOrdinal : cohort) {
if (exprOrdinal == i) {
// Already did this member of the cohort. It's a waste
// of effort to repeat.
continue;
}
final RexNode cohortExpr = exprs[exprOrdinal];
int cohortLevel = maxInputFinder.maxInputFor(cohortExpr);
if (cohortLevel > level) {
level = cohortLevel;
}
}
}
// Try to implement this expression at this level.
// If that is not possible, try to implement it at higher levels.
levelLoop:
for (;; ++level) {
if (level >= levelCount) {
// This is a new level. We can use any type we like.
for (int relTypeOrdinal = 0;
relTypeOrdinal < relTypes.length;
relTypeOrdinal++) {
if (!relTypesPossibleForTopLevel[relTypeOrdinal]) {
continue;
}
if (relTypes[relTypeOrdinal].canImplement(
expr,
condition)) {
// Success. We have found a type where we can
// implement this expression.
exprLevels[i] = level;
levelTypeOrdinals[level] = relTypeOrdinal;
assert (level == 0)
|| (levelTypeOrdinals[level - 1]
!= levelTypeOrdinals[level])
: "successive levels of same type";
// Figure out which of the other reltypes are
// still possible for this level.
// Previous reltypes are not possible.
for (int j = 0; j < relTypeOrdinal; ++j) {
relTypesPossibleForTopLevel[j] = false;
}
// Successive reltypes may be possible.
for (int j = relTypeOrdinal + 1;
j < relTypes.length;
++j) {
if (relTypesPossibleForTopLevel[j]) {
relTypesPossibleForTopLevel[j] =
relTypes[j].canImplement(
expr,
condition);
}
}
// Move to next level.
levelTypeOrdinals[levelCount] =
firstSet(relTypesPossibleForTopLevel);
++levelCount;
Arrays.fill(relTypesPossibleForTopLevel, true);
break levelLoop;
}
}
// None of the reltypes still active for this level could
// implement expr. But maybe we could succeed with a new
// level, with all options open?
if (count(relTypesPossibleForTopLevel) >= relTypes.length) {
// Cannot implement for any type.
throw new AssertionError("cannot implement " + expr);
}
levelTypeOrdinals[levelCount] =
firstSet(relTypesPossibleForTopLevel);
++levelCount;
Arrays.fill(relTypesPossibleForTopLevel, true);
} else {
final int levelTypeOrdinal = levelTypeOrdinals[level];
if (!relTypes[levelTypeOrdinal].canImplement(
expr,
condition)) {
// Cannot implement this expression in this type;
// continue to next level.
continue;
}
exprLevels[i] = level;
break;
}
}
}
if (levelCount > 0) {
// The latest level should be CalcRelType otherwise literals cannot be
// implemented.
assert "CalcRelType".equals(relTypes[0].name)
: "The first RelType should be CalcRelType for proper RexLiteral"
+ " implementation at the last level, got " + relTypes[0].name;
if (levelTypeOrdinals[levelCount - 1] != 0) {
levelCount++;
}
}
return levelCount;
}
/**
* Computes the order in which to visit expressions, so that we decide the
* level of an expression only after the levels of lower expressions have
* been decided.
*
* First, we need to ensure that an expression is visited after all of
* its inputs.
*
*
Further, if the expression is a member of a cohort, we need to visit
* it after the inputs of all other expressions in that cohort. With this
* condition, expressions in the same cohort will very likely end up in the
* same level.
*
*
Note that if there are no cohorts, the expressions from the
* {@link RexProgram} are already in a suitable order. We perform the
* topological sort just to ensure that the code path is well-trodden.
*
* @param exprs Expressions
* @param cohorts List of cohorts, each of which is a set of expr ordinals
* @return Expression ordinals in topological order
*/
private static List computeTopologicalOrdering(
RexNode[] exprs,
List> cohorts) {
final DirectedGraph graph =
DefaultDirectedGraph.create();
for (int i = 0; i < exprs.length; i++) {
graph.addVertex(i);
}
for (int i = 0; i < exprs.length; i++) {
final RexNode expr = exprs[i];
final Set cohort = findCohort(cohorts, i);
final Set targets;
if (cohort == null) {
targets = Collections.singleton(i);
} else {
targets = cohort;
}
expr.accept(
new RexVisitorImpl(true) {
@Override public Void visitLocalRef(RexLocalRef localRef) {
for (Integer target : targets) {
graph.addEdge(localRef.getIndex(), target);
}
return null;
}
});
}
TopologicalOrderIterator iter =
new TopologicalOrderIterator<>(graph);
final List permutation = new ArrayList<>();
while (iter.hasNext()) {
permutation.add(iter.next());
}
return permutation;
}
/**
* Finds the cohort that contains the given integer, or returns null.
*
* @param cohorts List of cohorts, each a set of integers
* @param ordinal Integer to search for
* @return Cohort that contains the integer, or null if not found
*/
private static @Nullable Set findCohort(
List> cohorts,
int ordinal) {
for (Set cohort : cohorts) {
if (cohort.contains(ordinal)) {
return cohort;
}
}
return null;
}
private static int[] identityArray(int length) {
final int[] ints = new int[length];
for (int i = 0; i < ints.length; i++) {
ints[i] = i;
}
return ints;
}
/**
* Creates a program containing the expressions for a given level.
*
* The expression list of the program will consist of all entries in the
* expression list allExprs[i] for which the corresponding
* level ordinal exprLevels[i] is equal to level.
* Expressions are mapped according to inputExprOrdinals.
*
* @param level Level ordinal
* @param levelCount Number of levels
* @param inputRowType Input row type
* @param allExprs Array of all expressions
* @param exprLevels Array of the level ordinal of each expression
* @param inputExprOrdinals Ordinals in the expression list of input
* expressions. Input expression i
* will be found at position
* inputExprOrdinals[i].
* @param projectExprOrdinals Ordinals of the expressions to be output this
* level.
* @param conditionExprOrdinal Ordinal of the expression to form the
* condition for this level, or -1 if there is no
* condition.
* @param outputRowType Output row type
* @return Relational expression
*/
private RexProgram createProgramForLevel(
int level,
int levelCount,
RelDataType inputRowType,
RexNode[] allExprs,
int[] exprLevels,
int[] inputExprOrdinals,
final int[] projectExprOrdinals,
int conditionExprOrdinal,
@Nullable RelDataType outputRowType) {
// Build a list of expressions to form the calc.
List exprs = new ArrayList<>();
// exprInverseOrdinals describes where an expression in allExprs comes
// from -- from an input, from a calculated expression, or -1 if not
// available at this level.
int[] exprInverseOrdinals = new int[allExprs.length];
Arrays.fill(exprInverseOrdinals, -1);
int j = 0;
// First populate the inputs. They were computed at some previous level
// and are used here.
for (int i = 0; i < inputExprOrdinals.length; i++) {
final int inputExprOrdinal = inputExprOrdinals[i];
exprs.add(
new RexInputRef(
i,
allExprs[inputExprOrdinal].getType()));
exprInverseOrdinals[inputExprOrdinal] = j;
++j;
}
// Next populate the computed expressions.
final RexShuttle shuttle =
new InputToCommonExprConverter(
exprInverseOrdinals,
exprLevels,
level,
inputExprOrdinals,
allExprs);
for (int i = 0; i < allExprs.length; i++) {
if (exprLevels[i] == level
|| exprLevels[i] == -1
&& level == (levelCount - 1)
&& allExprs[i] instanceof RexLiteral) {
RexNode expr = allExprs[i];
final RexNode translatedExpr = expr.accept(shuttle);
exprs.add(translatedExpr);
assert exprInverseOrdinals[i] == -1;
exprInverseOrdinals[i] = j;
++j;
}
}
// Form the projection and condition list. Project and condition
// ordinals are offsets into allExprs, so we need to map them into
// exprs.
final List projectRefs =
new ArrayList<>(projectExprOrdinals.length);
final List fieldNames =
new ArrayList<>(projectExprOrdinals.length);
for (int i = 0; i < projectExprOrdinals.length; i++) {
final int projectExprOrdinal = projectExprOrdinals[i];
final int index = exprInverseOrdinals[projectExprOrdinal];
assert index >= 0;
RexNode expr = allExprs[projectExprOrdinal];
projectRefs.add(new RexLocalRef(index, expr.getType()));
// Inherit meaningful field name if possible.
fieldNames.add(deriveFieldName(expr, i));
}
RexLocalRef conditionRef;
if (conditionExprOrdinal >= 0) {
final int index = exprInverseOrdinals[conditionExprOrdinal];
conditionRef =
new RexLocalRef(
index,
allExprs[conditionExprOrdinal].getType());
} else {
conditionRef = null;
}
if (outputRowType == null) {
outputRowType =
RexUtil.createStructType(typeFactory, projectRefs, fieldNames, null);
}
final RexProgram program =
new RexProgram(
inputRowType, exprs, projectRefs, conditionRef, outputRowType);
// Program is NOT normalized here (e.g. can contain literals in
// call operands), since literals should be inlined.
return program;
}
private String deriveFieldName(RexNode expr, int ordinal) {
if (expr instanceof RexInputRef) {
int inputIndex = ((RexInputRef) expr).getIndex();
String fieldName =
child.getRowType().getFieldList().get(inputIndex).getName();
// Don't inherit field names like '$3' from child: that's
// confusing.
if (!fieldName.startsWith("$") || fieldName.startsWith("$EXPR")) {
return fieldName;
}
}
return "$" + ordinal;
}
/**
* Traces the given array of level expression lists at the finer level.
*
* @param exprs Array expressions
* @param exprLevels For each expression, the ordinal of its level
* @param levelTypeOrdinals For each level, the ordinal of its type in
* the {@link #relTypes} array
* @param levelCount The number of levels
*/
private void traceLevelExpressions(
RexNode[] exprs,
int[] exprLevels,
int[] levelTypeOrdinals,
int levelCount) {
StringWriter traceMsg = new StringWriter();
PrintWriter traceWriter = new PrintWriter(traceMsg);
traceWriter.println("FarragoAutoCalcRule result expressions for: ");
traceWriter.println(program.toString());
for (int level = 0; level < levelCount; level++) {
traceWriter.println("Rel Level " + level
+ ", type " + relTypes[levelTypeOrdinals[level]]);
for (int i = 0; i < exprs.length; i++) {
RexNode expr = exprs[i];
assert (exprLevels[i] >= -1) && (exprLevels[i] < levelCount)
: "expression's level is out of range";
if (exprLevels[i] == level) {
traceWriter.println("\t" + i + ": " + expr);
}
}
traceWriter.println();
}
String msg = traceMsg.toString();
RULE_LOGGER.trace(msg);
}
/**
* Returns the number of bits set in an array.
*/
private static int count(boolean[] booleans) {
int count = 0;
for (boolean b : booleans) {
if (b) {
++count;
}
}
return count;
}
/**
* Returns the index of the first set bit in an array.
*/
private static int firstSet(boolean[] booleans) {
for (int i = 0; i < booleans.length; i++) {
if (booleans[i]) {
return i;
}
}
return -1;
}
/**
* Searches for a value in a map, and returns the position where it was
* found, or -1.
*
* @param value Value to search for
* @param map Map to search in
* @return Ordinal of value in map, or -1 if not found
*/
private static int indexOf(int value, int[] map) {
for (int i = 0; i < map.length; i++) {
if (value == map[i]) {
return i;
}
}
return -1;
}
/**
* Returns whether a relational expression can be implemented solely in a
* given {@link RelType}.
*
* @param rel Calculation relational expression
* @param relTypeName Name of a {@link RelType}
* @return Whether relational expression can be implemented
*/
protected boolean canImplement(LogicalCalc rel, String relTypeName) {
for (RelType relType : relTypes) {
if (relType.name.equals(relTypeName)) {
return relType.canImplement(rel.getProgram());
}
}
throw new AssertionError("unknown type " + relTypeName);
}
/**
* Returns a list of sets of expressions that should be on the same level.
*
* For example, if this method returns { {3, 5}, {4, 7} }, it means that
* expressions 3 and 5, should be on the same level, and expressions 4 and 7
* should be on the same level. The two cohorts do not need to be on the
* same level.
*
*
The list is best effort. If it is not possible to arrange that the
* expressions in a cohort are on the same level, the {@link #execute()}
* method will still succeed.
*
*
The default implementation of this method returns the empty list;
* expressions will be put on the most suitable level. This is generally
* the lowest possible level, except for literals, which are placed at the
* level where they are used.
*
* @return List of cohorts, that is sets of expressions, that the splitting
* algorithm should attempt to place on the same level
*/
protected List> getCohorts() {
return Collections.emptyList();
}
//~ Inner Classes ----------------------------------------------------------
/** Type of relational expression. Determines which kinds of
* expressions it can handle. */
public abstract static class RelType {
private final String name;
protected RelType(String name) {
this.name = name;
}
@Override public String toString() {
return name;
}
protected abstract boolean canImplement(RexFieldAccess field);
protected abstract boolean canImplement(RexDynamicParam param);
protected abstract boolean canImplement(RexLiteral literal);
protected abstract boolean canImplement(RexCall call);
protected boolean supportsCondition() {
return true;
}
protected RelNode makeRel(RelOptCluster cluster,
RelTraitSet traitSet, RelBuilder relBuilder, RelNode input,
RexProgram program) {
return LogicalCalc.create(input, program);
}
/**
* Returns whether this RelType can implement a given
* expression.
*
* @param expr Expression
* @param condition Whether expression is a condition
* @return Whether this RelType can implement a given
* expression.
*/
public boolean canImplement(RexNode expr, boolean condition) {
if (condition && !supportsCondition()) {
return false;
}
try {
expr.accept(new ImplementTester(this));
return true;
} catch (CannotImplement e) {
Util.swallow(e, null);
return false;
}
}
/**
* Returns whether this tester's RelType can implement a
* given program.
*
* @param program Program
* @return Whether this tester's RelType can implement a
* given program.
*/
public boolean canImplement(RexProgram program) {
if ((program.getCondition() != null)
&& !canImplement(program.getCondition(), true)) {
return false;
}
for (RexNode expr : program.getExprList()) {
if (!canImplement(expr, false)) {
return false;
}
}
return true;
}
}
/**
* Visitor which returns whether an expression can be implemented in a given
* type of relational expression.
*/
private static class ImplementTester extends RexVisitorImpl {
private final RelType relType;
ImplementTester(RelType relType) {
super(false);
this.relType = relType;
}
@Override public Void visitCall(RexCall call) {
if (!relType.canImplement(call)) {
throw CannotImplement.INSTANCE;
}
return null;
}
@Override public Void visitDynamicParam(RexDynamicParam dynamicParam) {
if (!relType.canImplement(dynamicParam)) {
throw CannotImplement.INSTANCE;
}
return null;
}
@Override public Void visitFieldAccess(RexFieldAccess fieldAccess) {
if (!relType.canImplement(fieldAccess)) {
throw CannotImplement.INSTANCE;
}
return null;
}
@Override public Void visitLiteral(RexLiteral literal) {
if (!relType.canImplement(literal)) {
throw CannotImplement.INSTANCE;
}
return null;
}
}
/**
* Control exception for {@link ImplementTester}.
*/
private static class CannotImplement extends RuntimeException {
@SuppressWarnings("ThrowableInstanceNeverThrown")
static final CannotImplement INSTANCE = new CannotImplement();
}
/**
* Shuttle which converts every reference to an input field in an expression
* to a reference to a common sub-expression.
*/
private static class InputToCommonExprConverter extends RexShuttle {
private final int[] exprInverseOrdinals;
private final int[] exprLevels;
private final int level;
private final int[] inputExprOrdinals;
private final RexNode[] allExprs;
InputToCommonExprConverter(
int[] exprInverseOrdinals,
int[] exprLevels,
int level,
int[] inputExprOrdinals,
RexNode[] allExprs) {
this.exprInverseOrdinals = exprInverseOrdinals;
this.exprLevels = exprLevels;
this.level = level;
this.inputExprOrdinals = inputExprOrdinals;
this.allExprs = allExprs;
}
@Override public RexNode visitInputRef(RexInputRef input) {
final int index = exprInverseOrdinals[input.getIndex()];
assert index >= 0;
return new RexLocalRef(
index,
input.getType());
}
@Override public RexNode visitLocalRef(RexLocalRef local) {
// A reference to a local variable becomes a reference to an input
// if the local was computed at a previous level.
final int localIndex = local.getIndex();
final int exprLevel = exprLevels[localIndex];
if (exprLevel < level) {
if (allExprs[localIndex] instanceof RexLiteral) {
// Expression is to be inlined. Use the original expression.
return allExprs[localIndex];
}
int inputIndex = indexOf(localIndex, inputExprOrdinals);
assert inputIndex >= 0;
return new RexLocalRef(
inputIndex,
local.getType());
} else {
// It's a reference to what was a local expression at the
// previous level, and was then projected.
final int exprIndex = exprInverseOrdinals[localIndex];
return new RexLocalRef(
exprIndex,
local.getType());
}
}
}
/**
* Finds the highest level used by any of the inputs of a given expression.
*/
private static class MaxInputFinder extends RexVisitorImpl {
int level;
private final int[] exprLevels;
MaxInputFinder(int[] exprLevels) {
super(true);
this.exprLevels = exprLevels;
}
@Override public Void visitLocalRef(RexLocalRef localRef) {
int inputLevel = exprLevels[localRef.getIndex()];
level = Math.max(level, inputLevel);
return null;
}
/**
* Returns the highest level of any of the inputs of an expression.
*/
public int maxInputFor(RexNode expr) {
level = 0;
expr.accept(this);
return level;
}
}
/**
* Builds an array of the highest level which contains an expression which
* uses each expression as an input.
*/
private static class HighestUsageFinder extends RexVisitorImpl {
private final int[] maxUsingLevelOrdinals;
private int currentLevel;
HighestUsageFinder(RexNode[] exprs, int[] exprLevels) {
super(true);
this.maxUsingLevelOrdinals = new int[exprs.length];
Arrays.fill(maxUsingLevelOrdinals, -1);
for (int i = 0; i < exprs.length; i++) {
if (exprs[i] instanceof RexLiteral) {
// Literals are always used directly. It never makes sense
// to compute them at a lower level and project them to
// where they are used.
maxUsingLevelOrdinals[i] = -1;
continue;
}
currentLevel = exprLevels[i];
@SuppressWarnings("argument.type.incompatible")
final Void unused = exprs[i].accept(this);
}
}
public int[] getMaxUsingLevelOrdinals() {
return maxUsingLevelOrdinals;
}
@Override public Void visitLocalRef(RexLocalRef ref) {
final int index = ref.getIndex();
maxUsingLevelOrdinals[index] =
Math.max(maxUsingLevelOrdinals[index], currentLevel);
return null;
}
}
}