ShowCommand.java

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// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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package org.apache.doris.nereids.trees.plans.commands;

import org.apache.doris.analysis.RedirectStatus;
import org.apache.doris.analysis.StmtType;
import org.apache.doris.common.AnalysisException;
import org.apache.doris.common.util.OrderByPair;
import org.apache.doris.nereids.analyzer.UnboundSlot;
import org.apache.doris.nereids.properties.OrderKey;
import org.apache.doris.nereids.trees.plans.PlanType;
import org.apache.doris.qe.ConnectContext;
import org.apache.doris.qe.ResultSetMetaData;
import org.apache.doris.qe.ShowResultSet;
import org.apache.doris.qe.ShowResultSetMetaData;
import org.apache.doris.qe.StmtExecutor;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;

import java.util.ArrayList;
import java.util.List;

/**
 * base class for all show commands
 */
public abstract class ShowCommand extends Command implements Redirect {
    public ShowCommand(PlanType type) {
        super(type);
    }

    @Override
    public StmtType stmtType() {
        return StmtType.SHOW;
    }

    @Override
    public void run(ConnectContext ctx, StmtExecutor executor) throws Exception {
        ShowResultSet resultSet = doRun(ctx, executor);
        if (resultSet != null) {
            if (executor.isProxy()) {
                executor.setProxyShowResultSet(resultSet);
            } else {
                executor.sendResultSet(resultSet);
            }
        }
    }

    public abstract ShowResultSetMetaData getMetaData();

    /**
     * get order by pairs in show command
     */
    public ArrayList<OrderByPair> getOrderByPairs(List<OrderKey> orderKeys,
                                                      ImmutableList<String> titles) throws AnalysisException {
        ArrayList<OrderByPair> orderByPairs = null;
        if (orderKeys != null && !orderKeys.isEmpty()) {
            orderByPairs = new ArrayList<>();
            for (OrderKey orderKey : orderKeys) {
                if (!(orderKey.getExpr() instanceof UnboundSlot)) {
                    throw new AnalysisException("Should order by column");
                }

                UnboundSlot slot = (UnboundSlot) orderKey.getExpr();
                if (slot != null) {
                    String colName = slot.getName();

                    // analyze column
                    int index = -1;
                    for (String title : titles) {
                        if (title.equalsIgnoreCase(colName)) {
                            index = titles.indexOf(title);
                        }
                    }
                    if (index == -1) {
                        throw new AnalysisException("Title name[" + colName + "] does not exist");
                    }

                    OrderByPair orderByPair = new OrderByPair(index, !orderKey.isAsc());
                    orderByPairs.add(orderByPair);
                }
            }
        }
        return orderByPairs;
    }

    /**
     * apply limit and offset in show command
     */
    public List<List<String>> applyLimit(long limit, long offset, List<List<String>> showResult) {
        if (showResult == null) {
            return Lists.newArrayList();
        }

        long offsetValue = offset == -1L ? 0 : offset;
        if (offsetValue >= showResult.size()) {
            showResult = Lists.newArrayList();
        } else if (limit != -1L) {
            if ((limit + offsetValue) < showResult.size()) {
                showResult = showResult.subList((int) offsetValue, (int) (limit + offsetValue));
            } else {
                showResult = showResult.subList((int) offsetValue, showResult.size());
            }
        }
        return showResult;
    }

    @Override
    public ResultSetMetaData getResultSetMetaData() {
        return getMetaData();
    }

    @Override
    public RedirectStatus toRedirectStatus() {
        return RedirectStatus.NO_FORWARD;
    }

    public abstract ShowResultSet doRun(ConnectContext ctx, StmtExecutor executor) throws Exception;

}