DescribeOutputRewrite.java

/*
 * Licensed 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.facebook.presto.sql.rewrite;

import com.facebook.presto.Session;
import com.facebook.presto.common.QualifiedObjectName;
import com.facebook.presto.common.type.FixedWidthType;
import com.facebook.presto.metadata.Metadata;
import com.facebook.presto.spi.WarningCollector;
import com.facebook.presto.spi.security.AccessControl;
import com.facebook.presto.sql.analyzer.Analysis;
import com.facebook.presto.sql.analyzer.Analyzer;
import com.facebook.presto.sql.analyzer.Field;
import com.facebook.presto.sql.analyzer.QueryExplainer;
import com.facebook.presto.sql.parser.SqlParser;
import com.facebook.presto.sql.tree.AstVisitor;
import com.facebook.presto.sql.tree.BooleanLiteral;
import com.facebook.presto.sql.tree.DescribeOutput;
import com.facebook.presto.sql.tree.Expression;
import com.facebook.presto.sql.tree.LongLiteral;
import com.facebook.presto.sql.tree.Node;
import com.facebook.presto.sql.tree.NodeRef;
import com.facebook.presto.sql.tree.NullLiteral;
import com.facebook.presto.sql.tree.Parameter;
import com.facebook.presto.sql.tree.Row;
import com.facebook.presto.sql.tree.Statement;
import com.facebook.presto.sql.tree.StringLiteral;
import com.google.common.collect.ImmutableList;

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

import static com.facebook.presto.sql.QueryUtil.aliased;
import static com.facebook.presto.sql.QueryUtil.identifier;
import static com.facebook.presto.sql.QueryUtil.row;
import static com.facebook.presto.sql.QueryUtil.selectList;
import static com.facebook.presto.sql.QueryUtil.simpleQuery;
import static com.facebook.presto.sql.QueryUtil.values;
import static com.facebook.presto.util.AnalyzerUtil.createParsingOptions;
import static java.util.Objects.requireNonNull;

final class DescribeOutputRewrite
        implements StatementRewrite.Rewrite
{
    @Override
    public Statement rewrite(
            Session session,
            Metadata metadata,
            SqlParser parser,
            Optional<QueryExplainer> queryExplainer,
            Statement node,
            List<Expression> parameters,
            Map<NodeRef<Parameter>, Expression> parameterLookup,
            AccessControl accessControl,
            WarningCollector warningCollector,
            String query)
    {
        return (Statement) new Visitor(session, parser, metadata, queryExplainer, parameters, parameterLookup, accessControl, warningCollector, query).process(node, null);
    }

    private static final class Visitor
            extends AstVisitor<Node, Void>
    {
        private final Session session;
        private final SqlParser parser;
        private final Metadata metadata;
        private final Optional<QueryExplainer> queryExplainer;
        private final List<Expression> parameters;
        private final Map<NodeRef<Parameter>, Expression> parameterLookup;
        private final AccessControl accessControl;
        private final WarningCollector warningCollector;
        private final String query;

        public Visitor(
                Session session,
                SqlParser parser,
                Metadata metadata,
                Optional<QueryExplainer> queryExplainer,
                List<Expression> parameters,
                Map<NodeRef<Parameter>, Expression> parameterLookup,
                AccessControl accessControl,
                WarningCollector warningCollector,
                String query)
        {
            this.session = requireNonNull(session, "session is null");
            this.parser = parser;
            this.metadata = metadata;
            this.queryExplainer = queryExplainer;
            this.parameters = parameters;
            this.parameterLookup = parameterLookup;
            this.accessControl = accessControl;
            this.warningCollector = requireNonNull(warningCollector, "warningCollector is null");
            this.query = requireNonNull(query, "query is null");
        }

        @Override
        protected Node visitDescribeOutput(DescribeOutput node, Void context)
        {
            String sqlString = session.getPreparedStatement(node.getName().getValue());
            Statement statement = parser.createStatement(sqlString, createParsingOptions(session, warningCollector));

            Analyzer analyzer = new Analyzer(session, metadata, parser, accessControl, queryExplainer, parameters, parameterLookup, warningCollector, query);
            Analysis analysis = analyzer.analyze(statement, true);

            Optional<String> limit = Optional.empty();
            Row[] rows = analysis.getRootScope().getRelationType().getVisibleFields().stream().map(field -> createDescribeOutputRow(field, analysis)).toArray(Row[]::new);
            if (rows.length == 0) {
                NullLiteral nullLiteral = new NullLiteral();
                rows = new Row[] {row(nullLiteral, nullLiteral, nullLiteral, nullLiteral, nullLiteral, nullLiteral, nullLiteral)};
                limit = Optional.of("0");
            }
            return simpleQuery(
                    selectList(
                            identifier("Column Name"),
                            identifier("Catalog"),
                            identifier("Schema"),
                            identifier("Table"),
                            identifier("Type"),
                            identifier("Type Size"),
                            identifier("Aliased")),
                    aliased(
                            values(rows),
                            "Statement Output",
                            ImmutableList.of("Column Name", "Catalog", "Schema", "Table", "Type", "Type Size", "Aliased")),
                    Optional.empty(),
                    Optional.empty(),
                    Optional.empty(),
                    Optional.empty(),
                    Optional.empty(),
                    limit);
        }

        private static Row createDescribeOutputRow(Field field, Analysis analysis)
        {
            LongLiteral typeSize = new LongLiteral("0");
            if (field.getType() instanceof FixedWidthType) {
                typeSize = new LongLiteral(String.valueOf(((FixedWidthType) field.getType()).getFixedSize()));
            }

            String columnName;
            if (field.getName().isPresent()) {
                columnName = field.getName().get();
            }
            else {
                int columnIndex = ImmutableList.copyOf(analysis.getOutputDescriptor().getVisibleFields()).indexOf(field);
                columnName = "_col" + columnIndex;
            }

            Optional<QualifiedObjectName> originTable = field.getOriginTable();

            return row(
                    new StringLiteral(columnName),
                    new StringLiteral(originTable.map(QualifiedObjectName::getCatalogName).orElse("")),
                    new StringLiteral(originTable.map(QualifiedObjectName::getSchemaName).orElse("")),
                    new StringLiteral(originTable.map(QualifiedObjectName::getObjectName).orElse("")),
                    new StringLiteral(field.getType().getDisplayName()),
                    typeSize,
                    new BooleanLiteral(String.valueOf(field.isAliased())));
        }

        @Override
        protected Node visitNode(Node node, Void context)
        {
            return node;
        }
    }
}