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SQL support for Querydsl
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/*
 * Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
 *
 * 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.querydsl.sql;

import com.querydsl.core.QueryFlag;
import com.querydsl.core.QueryFlag.Position;
import com.querydsl.core.QueryMetadata;
import com.querydsl.core.types.Expression;
import com.querydsl.core.types.FactoryExpression;
import com.querydsl.core.types.FactoryExpressionUtils;
import com.querydsl.core.types.Ops;
import com.querydsl.core.types.OrderSpecifier;
import com.querydsl.core.types.Path;
import com.querydsl.core.types.Projections;
import com.querydsl.core.types.dsl.Expressions;
import java.util.Map;
import java.util.Set;

/**
 * {@code SQLServer2005Templates} is an SQL dialect for Microsoft SQL Server 2005
 *
 * @author tiwe
 */
public class SQLServer2005Templates extends SQLServerTemplates {

  @SuppressWarnings("FieldNameHidesFieldInSuperclass") // Intentional
  public static final SQLServer2005Templates DEFAULT = new SQLServer2005Templates();

  public static Builder builder() {
    return new Builder() {
      @Override
      protected SQLTemplates build(char escape, boolean quote) {
        return new SQLServer2005Templates(escape, quote);
      }
    };
  }

  private String topTemplate = "top ({0}) ";

  private String outerQueryStart = "select * from (\n  ";

  private String outerQueryEnd = ") a where ";

  private String limitOffsetTemplate = "rn > {0} and rn <= {1}";

  private String offsetTemplate = "rn > {0}";

  private String outerQuerySuffix = " order by rn";

  public SQLServer2005Templates() {
    this(Keywords.SQLSERVER2005, '\\', false);
  }

  public SQLServer2005Templates(boolean quote) {
    this(Keywords.SQLSERVER2005, '\\', quote);
  }

  public SQLServer2005Templates(char escape, boolean quote) {
    this(Keywords.SQLSERVER2005, escape, quote);
  }

  protected SQLServer2005Templates(Set keywords, char escape, boolean quote) {
    super(keywords, escape, quote);
    // The older MSSQL Server suite doesn't support logarithms with a base other
    // than 10 and the natural logarithm, so we do it manually
    add(Ops.MathOps.LOG, "(LOG({0}) / LOG({1}))");
  }

  @Override
  public void serialize(QueryMetadata metadata, boolean forCountRow, SQLSerializer context) {
    if (!forCountRow && metadata.getModifiers().isRestricting() && !metadata.getJoins().isEmpty()) {
      var mod = metadata.getModifiers();
      if (mod.getOffset() == null) {
        // select top ...
        metadata = metadata.clone();
        metadata.addFlag(
            new QueryFlag(
                QueryFlag.Position.AFTER_SELECT,
                Expressions.template(Integer.class, topTemplate, mod.getLimit())));
        context.serializeForQuery(metadata, forCountRow);
      } else {
        context.append(outerQueryStart);
        metadata = metadata.clone();
        var rn = SQLExpressions.rowNumber().over();
        for (OrderSpecifier os : metadata.getOrderBy()) {
          rn.orderBy(os);
        }
        if (metadata.getOrderBy().isEmpty()) {
          rn.orderBy(Expressions.currentTimestamp().asc());
        }
        FactoryExpression pr = Projections.appending(metadata.getProjection(), rn.as("rn"));
        metadata.setProjection(FactoryExpressionUtils.wrap(pr));
        metadata.clearOrderBy();
        context.serializeForQuery(metadata, forCountRow);
        context.append(outerQueryEnd);
        if (mod.getLimit() == null) {
          context.handle(offsetTemplate, mod.getOffset());
        } else {
          context.handle(limitOffsetTemplate, mod.getOffset(), mod.getLimit() + mod.getOffset());
        }
        context.append(outerQuerySuffix);
      }

    } else {
      context.serializeForQuery(metadata, forCountRow);
    }

    if (!metadata.getFlags().isEmpty()) {
      context.serialize(Position.END, metadata.getFlags());
    }
  }

  @Override
  public void serializeDelete(
      QueryMetadata metadata, RelationalPath entity, SQLSerializer context) {
    // limit
    var mod = metadata.getModifiers();
    if (mod.isRestricting()) {
      metadata = metadata.clone();
      metadata.addFlag(
          new QueryFlag(
              QueryFlag.Position.AFTER_SELECT,
              Expressions.template(Integer.class, topTemplate, mod.getLimit())));
    }

    context.serializeForDelete(metadata, entity);

    if (!metadata.getFlags().isEmpty()) {
      context.serialize(Position.END, metadata.getFlags());
    }
  }

  @Override
  public void serializeUpdate(
      QueryMetadata metadata,
      RelationalPath entity,
      Map, Expression> updates,
      SQLSerializer context) {
    // limit
    var mod = metadata.getModifiers();
    if (mod.isRestricting()) {
      metadata = metadata.clone();
      metadata.addFlag(
          new QueryFlag(
              QueryFlag.Position.AFTER_SELECT,
              Expressions.template(Integer.class, topTemplate, mod.getLimit())));
    }

    context.serializeForUpdate(metadata, entity, updates);

    if (!metadata.getFlags().isEmpty()) {
      context.serialize(Position.END, metadata.getFlags());
    }
  }
}