NormalizeMatchInputs.java

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package org.apache.doris.nereids.rules.rewrite;

import org.apache.doris.nereids.rules.Rule;
import org.apache.doris.nereids.rules.RuleType;
import org.apache.doris.nereids.rules.analysis.MatchInputResolver;
import org.apache.doris.nereids.rules.analysis.MatchInputResolver.InputKind;
import org.apache.doris.nereids.rules.expression.AbstractExpressionRewriteRule;
import org.apache.doris.nereids.rules.expression.ExpressionRewrite;
import org.apache.doris.nereids.rules.expression.ExpressionRewriteContext;
import org.apache.doris.nereids.trees.expressions.Cast;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.Match;
import org.apache.doris.nereids.trees.expressions.NamedExpression;
import org.apache.doris.nereids.trees.plans.logical.LogicalOlapScan;
import org.apache.doris.nereids.types.StringType;

import com.google.common.collect.ImmutableList;

import java.util.List;
import java.util.stream.Collectors;

/** Restore scalar coercion after project/branch replacement, before checks and lowering. */
public class NormalizeMatchInputs extends ExpressionRewrite {
    private static final AbstractExpressionRewriteRule NORMALIZER = new AbstractExpressionRewriteRule() {
        @Override
        public Expression visitMatch(Match match, ExpressionRewriteContext context) {
            Match rewritten = (Match) super.visitMatch(match, context);
            Expression left = rewritten.left();
            if (left.getDataType().isVariantType()
                    && new MatchInputResolver(context.cascadesContext).resolve(left, context.plan.orElse(null))
                            == InputKind.SCALAR) {
                return rewritten.withChildren(new Cast(left, StringType.INSTANCE), rewritten.right());
            }
            return rewritten;
        }
    };

    public NormalizeMatchInputs() {
        super(NORMALIZER);
    }

    /** Normalize expressions at physical substitution sites without another plan traversal. */
    public static Expression normalize(Expression expression, ExpressionRewriteContext context) {
        return NORMALIZER.rewrite(expression, context);
    }

    @Override
    public List<Rule> buildRules() {
        // MATCH projections can already reside in scan virtual expressions at a late pass.
        Rule scanRule = logicalOlapScan().when(scan -> !scan.getVirtualColumns().isEmpty()).thenApply(ctx -> {
            LogicalOlapScan scan = ctx.root;
            ExpressionRewriteContext context = new ExpressionRewriteContext(scan, ctx.cascadesContext);
            List<NamedExpression> normalized = scan.getVirtualColumns().stream()
                    .map(expression -> (NamedExpression) rewrite(expression, context)).collect(Collectors.toList());
            return normalized.equals(scan.getVirtualColumns()) ? null : scan.withVirtualColumns(normalized);
        }).toRule(RuleType.NORMALIZE_MATCH_INPUTS);
        return ImmutableList.<Rule>builder().addAll(super.buildRules()).add(scanRule).build();
    }
}