/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.shardingsphere.sharding.distsql.parser.core;
  
  import org.antlr.v4.runtime.tree.ParseTree;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementBaseVisitor;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.AlgorithmDefinitionContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.AlterDefaultShardingStrategyContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.AlterShardingTableReferenceRuleContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.AlterShardingTableRuleContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.AuditDefinitionContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.AutoShardingColumnDefinitionContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.CountShardingRuleContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.CreateDefaultShardingStrategyContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.CreateShardingTableReferenceRuleContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.CreateShardingTableRuleContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.DataNodesContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.DatabaseNameContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.DropDefaultShardingStrategyContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.DropShardingAlgorithmContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.DropShardingAuditorContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.DropShardingKeyGeneratorContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.DropShardingTableReferenceRuleContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.DropShardingTableRuleContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.KeyGenerateDefinitionContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.PropertiesDefinitionContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.PropertyContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShardingAutoTableRuleContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShardingColumnDefinitionContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShardingStrategyContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShardingTableRuleContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShardingTableRuleDefinitionContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowDefaultShardingStrategyContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowShardingAlgorithmPluginsContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowShardingAlgorithmsContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowShardingAuditorsContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowShardingKeyGeneratorsContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowShardingTableNodesContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowShardingTableReferenceRulesContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowShardingTableRulesContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowShardingTableRulesUsedAlgorithmContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowShardingTableRulesUsedAuditorContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowShardingTableRulesUsedKeyGeneratorContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowUnusedShardingAlgorithmsContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowUnusedShardingAuditorsContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.ShowUnusedShardingKeyGeneratorsContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.SingleAuditDefinitionContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.StorageUnitsContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.TableNameContext;
  import org.apache.shardingsphere.distsql.parser.autogen.ShardingDistSQLStatementParser.TableReferenceRuleDefinitionContext;
  import org.apache.shardingsphere.distsql.segment.AlgorithmSegment;
  import org.apache.shardingsphere.distsql.statement.ral.queryable.show.ShowPluginsStatement;
  import org.apache.shardingsphere.distsql.statement.rql.rule.database.CountRuleStatement;
  import org.apache.shardingsphere.infra.database.core.metadata.database.enums.QuoteCharacter;
  import org.apache.shardingsphere.sharding.distsql.segment.strategy.AuditStrategySegment;
  import org.apache.shardingsphere.sharding.distsql.segment.strategy.KeyGenerateStrategySegment;
  import org.apache.shardingsphere.sharding.distsql.segment.strategy.ShardingAuditorSegment;
  import org.apache.shardingsphere.sharding.distsql.segment.strategy.ShardingStrategySegment;
  import org.apache.shardingsphere.sharding.distsql.segment.table.AbstractTableRuleSegment;
  import org.apache.shardingsphere.sharding.distsql.segment.table.AutoTableRuleSegment;
  import org.apache.shardingsphere.sharding.distsql.segment.table.TableReferenceRuleSegment;
  import org.apache.shardingsphere.sharding.distsql.segment.table.TableRuleSegment;
  import org.apache.shardingsphere.sharding.distsql.statement.AlterDefaultShardingStrategyStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.AlterShardingTableReferenceRuleStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.AlterShardingTableRuleStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.CreateDefaultShardingStrategyStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.CreateShardingTableReferenceRuleStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.CreateShardingTableRuleStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.DropDefaultShardingStrategyStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.DropShardingAlgorithmStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.DropShardingAuditorStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.DropShardingKeyGeneratorStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.DropShardingTableReferenceRuleStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.DropShardingTableRuleStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.ShowDefaultShardingStrategyStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.ShowShardingAlgorithmsStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.ShowShardingAuditorsStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.ShowShardingKeyGeneratorsStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.ShowShardingTableNodesStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.ShowShardingTableReferenceRulesStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.ShowShardingTableRulesStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.ShowShardingTableRulesUsedAlgorithmStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.ShowShardingTableRulesUsedAuditorStatement;
  import org.apache.shardingsphere.sharding.distsql.statement.ShowShardingTableRulesUsedKeyGeneratorStatement;
 import org.apache.shardingsphere.sharding.distsql.statement.ShowUnusedShardingAlgorithmsStatement;
 import org.apache.shardingsphere.sharding.distsql.statement.ShowUnusedShardingAuditorsStatement;
 import org.apache.shardingsphere.sharding.distsql.statement.ShowUnusedShardingKeyGeneratorsStatement;
 import org.apache.shardingsphere.sql.parser.api.ASTNode;
 import org.apache.shardingsphere.sql.parser.api.visitor.SQLVisitor;
 import org.apache.shardingsphere.sql.parser.statement.core.segment.dal.FromDatabaseSegment;
 import org.apache.shardingsphere.sql.parser.statement.core.segment.generic.DatabaseSegment;
 import org.apache.shardingsphere.sql.parser.statement.core.segment.generic.table.TableNameSegment;
 import org.apache.shardingsphere.sql.parser.statement.core.value.identifier.IdentifierValue;
 
 import java.util.Collection;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Properties;
 import java.util.stream.Collectors;
 
 /**
  * Sharding DistSQL statement visitor.
  */
 public final class ShardingDistSQLStatementVisitor extends ShardingDistSQLStatementBaseVisitor<ASTNode> implements SQLVisitor<ASTNode> {
     
     @Override
     public ASTNode visitCreateShardingTableRule(final CreateShardingTableRuleContext ctx) {
         Collection<AbstractTableRuleSegment> tableRuleSegments = ctx.shardingTableRuleDefinition().stream()
                 .map(each -> (AbstractTableRuleSegment) visit(each)).filter(Objects::nonNull).collect(Collectors.toList());
         return new CreateShardingTableRuleStatement(null != ctx.ifNotExists(), tableRuleSegments);
     }
     
     @Override
     public ASTNode visitCreateShardingTableReferenceRule(final CreateShardingTableReferenceRuleContext ctx) {
         return new CreateShardingTableReferenceRuleStatement(null != ctx.ifNotExists(), getTableReferenceRuleSegments(ctx.tableReferenceRuleDefinition()));
     }
     
     private Collection<TableReferenceRuleSegment> getTableReferenceRuleSegments(final List<TableReferenceRuleDefinitionContext> ctx) {
         Collection<TableReferenceRuleSegment> result = new LinkedList<>();
         for (TableReferenceRuleDefinitionContext each : ctx) {
             String ruleName = getIdentifierValue(each.ruleName());
             String reference = each.tableName().stream().map(this::getIdentifierValue).collect(Collectors.joining(","));
             result.add(new TableReferenceRuleSegment(ruleName, reference));
         }
         return result;
     }
     
     @Override
     public ASTNode visitAlterShardingTableRule(final AlterShardingTableRuleContext ctx) {
         List<AbstractTableRuleSegment> tableRuleSegments = ctx.shardingTableRuleDefinition().stream()
                 .map(each -> (AbstractTableRuleSegment) visit(each)).filter(Objects::nonNull).collect(Collectors.toList());
         return new AlterShardingTableRuleStatement(tableRuleSegments);
     }
     
     @Override
     public ASTNode visitAlterShardingTableReferenceRule(final AlterShardingTableReferenceRuleContext ctx) {
         return new AlterShardingTableReferenceRuleStatement(getTableReferenceRuleSegments(ctx.tableReferenceRuleDefinition()));
     }
     
     @Override
     public ASTNode visitDropShardingTableRule(final DropShardingTableRuleContext ctx) {
         return new DropShardingTableRuleStatement(null != ctx.ifExists(), ctx.tableName().stream().map(each -> (TableNameSegment) visit(each)).collect(Collectors.toList()));
     }
     
     @Override
     public ASTNode visitDropShardingTableReferenceRule(final DropShardingTableReferenceRuleContext ctx) {
         return new DropShardingTableReferenceRuleStatement(null != ctx.ifExists(), ctx.ruleName().stream().map(this::getIdentifierValue).collect(Collectors.toList()));
     }
     
     @Override
     public ASTNode visitCreateDefaultShardingStrategy(final CreateDefaultShardingStrategyContext ctx) {
         ShardingStrategyContext shardingStrategyContext = ctx.shardingStrategy();
         String defaultType = new IdentifierValue(ctx.type.getText()).getValue();
         String strategyType = getIdentifierValue(shardingStrategyContext.strategyType());
         if ("none".equalsIgnoreCase(strategyType)) {
             return new CreateDefaultShardingStrategyStatement(null != ctx.ifNotExists(), defaultType, "none", null, null);
         }
         AlgorithmSegment algorithmSegment = null == shardingStrategyContext.shardingAlgorithm().algorithmDefinition()
                 ? null
                 : (AlgorithmSegment) visitAlgorithmDefinition(shardingStrategyContext.shardingAlgorithm().algorithmDefinition());
         String shardingColumn = null == ctx.shardingStrategy().shardingColumnDefinition() ? null : buildShardingColumn(ctx.shardingStrategy().shardingColumnDefinition());
         return new CreateDefaultShardingStrategyStatement(null != ctx.ifNotExists(), defaultType, strategyType, shardingColumn, algorithmSegment);
     }
     
     @Override
     public ASTNode visitAlterDefaultShardingStrategy(final AlterDefaultShardingStrategyContext ctx) {
         String defaultType = new IdentifierValue(ctx.type.getText()).getValue();
         String strategyType = getIdentifierValue(ctx.shardingStrategy().strategyType());
         if ("none".equalsIgnoreCase(strategyType)) {
             return new AlterDefaultShardingStrategyStatement(defaultType, "none", null, null);
         }
         AlgorithmSegment algorithmSegment = null == ctx.shardingStrategy().shardingAlgorithm().algorithmDefinition()
                 ? null
                 : (AlgorithmSegment) visitAlgorithmDefinition(ctx.shardingStrategy().shardingAlgorithm().algorithmDefinition());
         String shardingColumn = null == ctx.shardingStrategy().shardingColumnDefinition() ? null : buildShardingColumn(ctx.shardingStrategy().shardingColumnDefinition());
         return new AlterDefaultShardingStrategyStatement(defaultType, strategyType, shardingColumn, algorithmSegment);
     }
     
     @Override
     public ASTNode visitDropDefaultShardingStrategy(final DropDefaultShardingStrategyContext ctx) {
         return new DropDefaultShardingStrategyStatement(null != ctx.ifExists(), new IdentifierValue(ctx.type.getText()).getValue().toLowerCase());
     }
     
     @Override
     public ASTNode visitDropShardingAlgorithm(final DropShardingAlgorithmContext ctx) {
         return new DropShardingAlgorithmStatement(null != ctx.ifExists(), ctx.shardingAlgorithmName().stream().map(this::getIdentifierValue).collect(Collectors.toList()));
     }
     
     @Override
     public ASTNode visitShowShardingTableRules(final ShowShardingTableRulesContext ctx) {
         return new ShowShardingTableRulesStatement(null == ctx.tableRule() ? null : getIdentifierValue(ctx.tableRule().tableName()),
                 null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitShowShardingAlgorithms(final ShowShardingAlgorithmsContext ctx) {
         return new ShowShardingAlgorithmsStatement(null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitShardingTableRuleDefinition(final ShardingTableRuleDefinitionContext ctx) {
         if (null != ctx.shardingTableRule()) {
             return visit(ctx.shardingTableRule());
         }
         if (null != ctx.shardingAutoTableRule()) {
             return visit(ctx.shardingAutoTableRule());
         }
         return null;
     }
     
     @Override
     public ASTNode visitShardingTableRule(final ShardingTableRuleContext ctx) {
         KeyGenerateStrategySegment keyGenerateSegment = null == ctx.keyGenerateDefinition() ? null : (KeyGenerateStrategySegment) visit(ctx.keyGenerateDefinition());
         AuditStrategySegment auditStrategySegment = null == ctx.auditDefinition() ? null : (AuditStrategySegment) visitAuditDefinition(getIdentifierValue(ctx.tableName()), ctx.auditDefinition());
         TableRuleSegment result = new TableRuleSegment(getIdentifierValue(ctx.tableName()), getDataNodes(ctx.dataNodes()), keyGenerateSegment, auditStrategySegment);
         Optional.ofNullable(ctx.tableStrategy()).ifPresent(optional -> result.setTableStrategySegment((ShardingStrategySegment) visit(ctx.tableStrategy().shardingStrategy())));
         Optional.ofNullable(ctx.databaseStrategy()).ifPresent(optional -> result.setDatabaseStrategySegment((ShardingStrategySegment) visit(ctx.databaseStrategy().shardingStrategy())));
         return result;
     }
     
     private ASTNode visitAuditDefinition(final String tableName, final AuditDefinitionContext ctx) {
         if (null == ctx) {
             return null;
         }
         Collection<ShardingAuditorSegment> shardingAuditorSegments = new LinkedList<>();
         int index = 0;
         for (SingleAuditDefinitionContext each : ctx.multiAuditDefinition().singleAuditDefinition()) {
             String algorithmTypeName = getIdentifierValue(each.algorithmDefinition().algorithmTypeName());
             String auditorName = String.format("%s_%s_%s", tableName, algorithmTypeName, index++).toLowerCase();
             shardingAuditorSegments.add(new ShardingAuditorSegment(auditorName, (AlgorithmSegment) visit(each.algorithmDefinition())));
         }
         return new AuditStrategySegment(shardingAuditorSegments, Boolean.parseBoolean(getIdentifierValue(ctx.auditAllowHintDisable())));
     }
     
     @Override
     public ASTNode visitShowShardingTableNodes(final ShowShardingTableNodesContext ctx) {
         return new ShowShardingTableNodesStatement(null == ctx.tableName() ? null : getIdentifierValue(ctx.tableName()),
                 null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitShardingAutoTableRule(final ShardingAutoTableRuleContext ctx) {
         AutoTableRuleSegment result = new AutoTableRuleSegment(getIdentifierValue(ctx.tableName()), getResources(ctx.storageUnits()));
         Optional.ofNullable(ctx.keyGenerateDefinition()).ifPresent(optional -> result.setKeyGenerateStrategySegment((KeyGenerateStrategySegment) visit(ctx.keyGenerateDefinition())));
         Optional.ofNullable(ctx.auditDefinition()).ifPresent(optional -> result.setAuditStrategySegment((AuditStrategySegment) visitAuditDefinition(getIdentifierValue(ctx.tableName()),
                 ctx.auditDefinition())));
         Optional.ofNullable(ctx.autoShardingColumnDefinition()).ifPresent(optional -> result.setShardingColumn(buildShardingColumn(ctx.autoShardingColumnDefinition())));
         Optional.ofNullable(ctx.algorithmDefinition()).ifPresent(optional -> result.setShardingAlgorithmSegment((AlgorithmSegment) visit(ctx.algorithmDefinition())));
         return result;
     }
     
     @Override
     public ASTNode visitKeyGenerateDefinition(final KeyGenerateDefinitionContext ctx) {
         return null == ctx ? null : new KeyGenerateStrategySegment(getIdentifierValue(ctx.columnName()), (AlgorithmSegment) visit(ctx.algorithmDefinition()));
     }
     
     @Override
     public ASTNode visitShardingStrategy(final ShardingStrategyContext ctx) {
         String strategyType = getIdentifierValue(ctx.strategyType());
         if ("none".equalsIgnoreCase(strategyType)) {
             return new ShardingStrategySegment(strategyType, null, null);
         }
         AlgorithmSegment algorithmSegment = null == ctx.shardingAlgorithm().algorithmDefinition() ? null : (AlgorithmSegment) visitAlgorithmDefinition(ctx.shardingAlgorithm().algorithmDefinition());
         String shardingColumn = null == ctx.shardingColumnDefinition() ? null : buildShardingColumn(ctx.shardingColumnDefinition());
         return new ShardingStrategySegment(strategyType, shardingColumn, algorithmSegment);
     }
     
     private Collection<String> getResources(final StorageUnitsContext ctx) {
         return ctx.storageUnit().stream().map(this::getIdentifierValue).collect(Collectors.toList());
     }
     
     private Collection<String> getDataNodes(final DataNodesContext ctx) {
         return ctx.dataNode().stream().map(this::getIdentifierValueForDataNodes).collect(Collectors.toList());
     }
     
     @Override
     public ASTNode visitAlgorithmDefinition(final AlgorithmDefinitionContext ctx) {
         return new AlgorithmSegment(getIdentifierValue(ctx.algorithmTypeName()), getProperties(ctx.propertiesDefinition()));
     }
     
     private String getIdentifierValue(final ParseTree context) {
         return null == context ? null : new IdentifierValue(context.getText()).getValue();
     }
     
     private String getIdentifierValueForDataNodes(final ParseTree context) {
         if (null == context) {
             return null;
         }
         String value = new IdentifierValue(context.getText()).getValue();
         return value.startsWith("'") ? value.substring(1, value.length() - 1) : value.trim();
     }
     
     private Properties getProperties(final PropertiesDefinitionContext ctx) {
         Properties result = new Properties();
         if (null == ctx || null == ctx.properties()) {
             return result;
         }
         for (PropertyContext each : ctx.properties().property()) {
             result.setProperty(QuoteCharacter.unwrapAndTrimText(each.key.getText()), QuoteCharacter.unwrapAndTrimText(each.value.getText()));
         }
         return result;
     }
     
     @Override
     public ASTNode visitTableName(final TableNameContext ctx) {
         return new TableNameSegment(ctx.getStart().getStartIndex(), ctx.getStop().getStopIndex(), new IdentifierValue(ctx.getText()));
     }
     
     @Override
     public ASTNode visitShowShardingTableReferenceRules(final ShowShardingTableReferenceRulesContext ctx) {
         return new ShowShardingTableReferenceRulesStatement(null == ctx.ruleName() ? null : getIdentifierValue(ctx.ruleName()),
                 null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitDatabaseName(final DatabaseNameContext ctx) {
         return new DatabaseSegment(ctx.getStart().getStartIndex(), ctx.getStop().getStopIndex(), new IdentifierValue(ctx.getText()));
     }
     
     @Override
     public ASTNode visitShowShardingKeyGenerators(final ShowShardingKeyGeneratorsContext ctx) {
         return new ShowShardingKeyGeneratorsStatement(
                 null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitDropShardingKeyGenerator(final DropShardingKeyGeneratorContext ctx) {
         return new DropShardingKeyGeneratorStatement(null != ctx.ifExists(), ctx.keyGeneratorName().stream().map(this::getIdentifierValue).collect(Collectors.toList()));
     }
     
     @Override
     public ASTNode visitDropShardingAuditor(final DropShardingAuditorContext ctx) {
         return new DropShardingAuditorStatement(null != ctx.ifExists(), ctx.auditorName().stream().map(this::getIdentifierValue).collect(Collectors.toList()));
     }
     
     @Override
     public ASTNode visitShowShardingAuditors(final ShowShardingAuditorsContext ctx) {
         return new ShowShardingAuditorsStatement(null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitShowDefaultShardingStrategy(final ShowDefaultShardingStrategyContext ctx) {
         return new ShowDefaultShardingStrategyStatement(null == ctx.databaseName()
                 ? null
                 : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitShowUnusedShardingAlgorithms(final ShowUnusedShardingAlgorithmsContext ctx) {
         return new ShowUnusedShardingAlgorithmsStatement(
                 null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     private String buildShardingColumn(final AutoShardingColumnDefinitionContext ctx) {
         return null == ctx.shardingColumn() ? null : getIdentifierValue(ctx.shardingColumn().columnName());
     }
     
     private String buildShardingColumn(final ShardingColumnDefinitionContext ctx) {
         String result = Optional.ofNullable(ctx.shardingColumn()).map(optional -> getIdentifierValue(optional.columnName()))
                 .orElseGet(() -> ctx.shardingColumns().columnName().stream().map(this::getIdentifierValue).collect(Collectors.joining(",")));
         return result.isEmpty() ? null : result;
     }
     
     @Override
     public ASTNode visitShowUnusedShardingKeyGenerators(final ShowUnusedShardingKeyGeneratorsContext ctx) {
         return new ShowUnusedShardingKeyGeneratorsStatement(
                 null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitShowUnusedShardingAuditors(final ShowUnusedShardingAuditorsContext ctx) {
         return new ShowUnusedShardingAuditorsStatement(
                 null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitShowShardingTableRulesUsedAlgorithm(final ShowShardingTableRulesUsedAlgorithmContext ctx) {
         return new ShowShardingTableRulesUsedAlgorithmStatement(getIdentifierValue(ctx.shardingAlgorithmName()),
                 null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitShowShardingTableRulesUsedKeyGenerator(final ShowShardingTableRulesUsedKeyGeneratorContext ctx) {
         return new ShowShardingTableRulesUsedKeyGeneratorStatement(getIdentifierValue(ctx.keyGeneratorName()),
                 null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitShowShardingTableRulesUsedAuditor(final ShowShardingTableRulesUsedAuditorContext ctx) {
         return new ShowShardingTableRulesUsedAuditorStatement(getIdentifierValue(ctx.auditorName()),
                 null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())));
     }
     
     @Override
     public ASTNode visitCountShardingRule(final CountShardingRuleContext ctx) {
         return new CountRuleStatement(null == ctx.databaseName() ? null : new FromDatabaseSegment(ctx.FROM().getSymbol().getStartIndex(), (DatabaseSegment) visit(ctx.databaseName())), "SHARDING");
     }
     
     @Override
     public ASTNode visitShowShardingAlgorithmPlugins(final ShowShardingAlgorithmPluginsContext ctx) {
         return new ShowPluginsStatement("SHARDING_ALGORITHM");
     }
 }