ReplaceVariableByLiteral.java

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

import org.apache.doris.nereids.SqlCacheContext;
import org.apache.doris.nereids.StatementContext;
import org.apache.doris.nereids.rules.expression.ExpressionPatternMatcher;
import org.apache.doris.nereids.rules.expression.ExpressionPatternRuleFactory;
import org.apache.doris.nereids.rules.expression.ExpressionRuleType;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.Variable;

import com.google.common.collect.ImmutableList;

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

/**
 * replace varaible to real expression
 */
public class ReplaceVariableByLiteral implements ExpressionPatternRuleFactory {
    public static ReplaceVariableByLiteral INSTANCE = new ReplaceVariableByLiteral();

    @Override
    public List<ExpressionPatternMatcher<? extends Expression>> buildRules() {
        return ImmutableList.of(
            matchesType(Variable.class).thenApply(ctx -> {
                StatementContext statementContext = ctx.cascadesContext.getStatementContext();
                Variable variable = ctx.expr;
                Optional<SqlCacheContext> sqlCacheContext = statementContext.getSqlCacheContext();
                if (sqlCacheContext.isPresent()) {
                    sqlCacheContext.get().addUsedVariable(variable);
                }
                return variable.getRealExpression();
            }).toRule(ExpressionRuleType.REPLACE_VARIABLE_BY_LITERAL)
        );
    }
}