LogicalSetOperation.java

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package org.apache.doris.nereids.trees.plans.logical;

import org.apache.doris.nereids.exceptions.AnalysisException;
import org.apache.doris.nereids.memo.GroupExpression;
import org.apache.doris.nereids.properties.LogicalProperties;
import org.apache.doris.nereids.rules.rewrite.PushProjectThroughUnion;
import org.apache.doris.nereids.trees.expressions.Alias;
import org.apache.doris.nereids.trees.expressions.Cast;
import org.apache.doris.nereids.trees.expressions.ExprId;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.NamedExpression;
import org.apache.doris.nereids.trees.expressions.Slot;
import org.apache.doris.nereids.trees.expressions.SlotReference;
import org.apache.doris.nereids.trees.expressions.StatementScopeIdGenerator;
import org.apache.doris.nereids.trees.plans.Plan;
import org.apache.doris.nereids.trees.plans.PlanType;
import org.apache.doris.nereids.trees.plans.algebra.SetOperation;
import org.apache.doris.nereids.trees.plans.visitor.PlanVisitor;
import org.apache.doris.nereids.types.DataType;
import org.apache.doris.nereids.util.TypeCoercionUtils;

import com.google.common.collect.ImmutableList;

import java.util.List;
import java.util.Objects;
import java.util.Optional;

/**
 * Logical SetOperation.
 * The type can have any number of children.
 * After parse, there will only be two children.
 * But after rewriting rules such as merging of the same nodes and elimination of oneRowRelation,
 * there will be multiple or no children.
 * <p>
 * eg: select k1, k2 from t1 union select 1, 2 union select d1, d2 from t2;
 */
public abstract class LogicalSetOperation extends AbstractLogicalPlan
        implements SetOperation, OutputSavePoint, ProjectProcessor {

    // eg value: qualifier:DISTINCT
    protected final Qualifier qualifier;
    // The newly created output column, used to display the output.
    // eg value: outputs:[k1, k2]
    protected final List<NamedExpression> outputs;
    protected final List<List<SlotReference>> regularChildrenOutputs;

    public LogicalSetOperation(PlanType planType, Qualifier qualifier, List<Plan> children) {
        super(planType, children);
        this.qualifier = qualifier;
        this.outputs = ImmutableList.of();
        this.regularChildrenOutputs = ImmutableList.of();
    }

    public LogicalSetOperation(PlanType planType, Qualifier qualifier,
            List<NamedExpression> outputs, List<List<SlotReference>> regularChildrenOutputs, List<Plan> children) {
        super(planType, children);
        this.qualifier = qualifier;
        this.outputs = ImmutableList.copyOf(outputs);
        this.regularChildrenOutputs = ImmutableList.copyOf(regularChildrenOutputs);
    }

    public LogicalSetOperation(PlanType planType, Qualifier qualifier, List<NamedExpression> outputs,
            List<List<SlotReference>> regularChildrenOutputs,
            Optional<GroupExpression> groupExpression, Optional<LogicalProperties> logicalProperties,
            List<Plan> children) {
        super(planType, groupExpression, logicalProperties, children.toArray(new Plan[0]));
        this.qualifier = qualifier;
        this.outputs = ImmutableList.copyOf(outputs);
        this.regularChildrenOutputs = ImmutableList.copyOf(regularChildrenOutputs);
    }

    public List<List<SlotReference>> getRegularChildrenOutputs() {
        return regularChildrenOutputs;
    }

    @Override
    public boolean hasUnboundExpression() {
        return outputs.isEmpty();
    }

    @Override
    public List<Slot> computeOutput() {
        return outputs.stream()
                .map(NamedExpression::toSlot)
                .collect(ImmutableList.toImmutableList());
    }

    public List<List<NamedExpression>> collectChildrenProjections() {
        return castCommonDataTypeOutputs();
    }

    /**
     * Generate new output for SetOperation.
     */
    public List<NamedExpression> buildNewOutputs() {
        List<Slot> slots = resetNullableForLeftOutputs();
        ImmutableList.Builder<NamedExpression> newOutputs = ImmutableList.builderWithExpectedSize(slots.size());

        for (int i = 0; i < slots.size(); i++) {
            Slot slot = slots.get(i);
            ExprId exprId = i < outputs.size() ? outputs.get(i).getExprId() : StatementScopeIdGenerator.newExprId();
            newOutputs.add(
                    new SlotReference(exprId, slot.toSql(), slot.getDataType(), slot.nullable(), ImmutableList.of())
            );
        }
        return newOutputs.build();
    }

    // If the right child is nullable, need to ensure that the left child is also nullable
    private List<Slot> resetNullableForLeftOutputs() {
        int rightChildOutputSize = child(1).getOutput().size();
        ImmutableList.Builder<Slot> resetNullableForLeftOutputs
                = ImmutableList.builderWithExpectedSize(rightChildOutputSize);
        for (int i = 0; i < rightChildOutputSize; ++i) {
            if (child(1).getOutput().get(i).nullable() && !child(0).getOutput().get(i).nullable()) {
                resetNullableForLeftOutputs.add(child(0).getOutput().get(i).withNullable(true));
            } else {
                resetNullableForLeftOutputs.add(child(0).getOutput().get(i));
            }
        }
        return resetNullableForLeftOutputs.build();
    }

    private List<List<NamedExpression>> castCommonDataTypeOutputs() {
        int childOutputSize = child(0).getOutput().size();
        ImmutableList.Builder<NamedExpression> newLeftOutputs = ImmutableList.builderWithExpectedSize(
                childOutputSize);
        ImmutableList.Builder<NamedExpression> newRightOutputs = ImmutableList.builderWithExpectedSize(
                childOutputSize
        );
        // Ensure that the output types of the left and right children are consistent and expand upward.
        for (int i = 0; i < childOutputSize; ++i) {
            Slot left = child(0).getOutput().get(i);
            Slot right = child(1).getOutput().get(i);
            DataType compatibleType;
            try {
                compatibleType = getAssignmentCompatibleType(left.getDataType(), right.getDataType());
            } catch (Exception e) {
                throw new AnalysisException(
                        "Can not find compatible type for " + left + " and " + right + ", " + e.getMessage());
            }
            Expression newLeft = TypeCoercionUtils.castIfNotSameTypeStrict(left, compatibleType);
            Expression newRight = TypeCoercionUtils.castIfNotSameTypeStrict(right, compatibleType);
            if (newLeft instanceof Cast) {
                newLeft = new Alias(newLeft, left.getName());
            }
            if (newRight instanceof Cast) {
                newRight = new Alias(newRight, right.getName());
            }
            newLeftOutputs.add((NamedExpression) newLeft);
            newRightOutputs.add((NamedExpression) newRight);
        }

        return ImmutableList.of(newLeftOutputs.build(), newRightOutputs.build());
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        LogicalSetOperation that = (LogicalSetOperation) o;
        return qualifier == that.qualifier && Objects.equals(outputs, that.outputs)
                && Objects.equals(regularChildrenOutputs, that.regularChildrenOutputs);
    }

    @Override
    public int hashCode() {
        return Objects.hash(qualifier, outputs, regularChildrenOutputs);
    }

    @Override
    public <R, C> R accept(PlanVisitor<R, C> visitor, C context) {
        return visitor.visitLogicalSetOperation(this, context);
    }

    @Override
    public List<? extends Expression> getExpressions() {
        return regularChildrenOutputs.stream().flatMap(List::stream).collect(ImmutableList.toImmutableList());
    }

    @Override
    public Qualifier getQualifier() {
        return qualifier;
    }

    @Override
    public List<SlotReference> getRegularChildOutput(int i) {
        return regularChildrenOutputs.get(i);
    }

    @Override
    public List<NamedExpression> getOutputs() {
        return outputs;
    }

    public abstract LogicalSetOperation withChildrenAndTheirOutputs(
            List<Plan> children, List<List<SlotReference>> childrenOutputs);

    public abstract LogicalSetOperation withNewOutputs(List<NamedExpression> newOutputs);

    @Override
    public int getArity() {
        return children.size();
    }

    /** getAssignmentCompatibleType */
    public static DataType getAssignmentCompatibleType(DataType left, DataType right) {
        Optional<DataType> commonType = TypeCoercionUtils.findWiderTypeForTwo(left, right, false);
        if (commonType.isPresent()) {
            return commonType.get();
        }
        throw new AnalysisException("Can not find assignment compatible type between "
                + left + " and " + right + "in set operation");
    }

    @Override
    public boolean canProcessProject(List<NamedExpression> parentProjects) {
        return PushProjectThroughUnion.canPushProject(parentProjects, this);
    }

    @Override
    public Optional<Plan> processProject(List<NamedExpression> parentProjects) {
        return Optional.of(PushProjectThroughUnion.doPushProject(parentProjects, this));
    }
}