content: /*
   * Copyright (C) 2010-2101 Alibaba Group Holding Limited.
   *
   * 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.alibaba.otter.node.etl.common.db.dialect;
  
  /**
   * 默认的基于标准SQL实现的CRUD sql封装
   * 
   * @author jianghang 2011-10-27 下午01:37:00
   * @version 4.0.0
   */
  public abstract class AbstractSqlTemplate implements SqlTemplate {
  
      private static final String DOT = ".";
  
      public String getSelectSql(String schemaName, String tableName, String[] pkNames, String[] columnNames) {
          StringBuilder sql = new StringBuilder("select ");
          int size = columnNames.length;
          for (int i = 0; i < size; i++) {
              sql.append(appendEscape(columnNames[i])).append((i + 1 < size) ? " , " : "");
          }
  
          sql.append(" from ").append(getFullName(schemaName, tableName)).append(" where ( ");
          appendColumnEquals(sql, pkNames, "and");
          sql.append(" ) ");
          return sql.toString().intern();// 不使用intern，避免方法区内存消耗过多
      }
  
      public String getUpdateSql(String schemaName, String tableName, String[] pkNames, String[] columnNames, boolean updatePks, String shardColumn) {
          StringBuilder sql = new StringBuilder("update " + getFullName(schemaName, tableName) + " set ");
          appendExcludeSingleShardColumnEquals(sql, columnNames, ",", updatePks, shardColumn);
          sql.append(" where (");
          appendColumnEquals(sql, pkNames, "and");
          sql.append(")");
          return sql.toString().intern(); // 不使用intern，避免方法区内存消耗过多
      }
  
      public String getInsertSql(String schemaName, String tableName, String[] pkNames, String[] columnNames) {
          StringBuilder sql = new StringBuilder("insert into " + getFullName(schemaName, tableName) + "(");
          String[] allColumns = new String[pkNames.length + columnNames.length];
          System.arraycopy(columnNames, 0, allColumns, 0, columnNames.length);
          System.arraycopy(pkNames, 0, allColumns, columnNames.length, pkNames.length);
  
          int size = allColumns.length;
          for (int i = 0; i < size; i++) {
              sql.append(appendEscape(allColumns[i])).append((i + 1 < size) ? "," : "");
          }
  
          sql.append(") values (");
          appendColumnQuestions(sql, allColumns);
          sql.append(")");
          return sql.toString().intern();// intern优化，避免出现大量相同的字符串
      }
  
      public String getDeleteSql(String schemaName, String tableName, String[] pkNames) {
          StringBuilder sql = new StringBuilder("delete from " + getFullName(schemaName, tableName) + " where ");
          appendColumnEquals(sql, pkNames, "and");
          return sql.toString().intern();// intern优化，避免出现大量相同的字符串
      }
  
      protected String getFullName(String schemaName, String tableName) {
          StringBuilder sb = new StringBuilder();
          if (schemaName != null) {
              sb.append(appendEscape(schemaName)).append(DOT);
          }
          sb.append(appendEscape(tableName));
          return sb.toString().intern();
      }
  
      // ================ helper method ============
  
      protected String appendEscape(String columnName) {
          return columnName;
      }
  
      protected void appendColumnQuestions(StringBuilder sql, String[] columns) {
          int size = columns.length;
          for (int i = 0; i < size; i++) {
              sql.append("?").append((i + 1 < size) ? " , " : "");
          }
      }
  
      protected void appendColumnEquals(StringBuilder sql, String[] columns, String separator) {
          int size = columns.length;
          for (int i = 0; i < size; i++) {
              sql.append(" ").append(appendEscape(columns[i])).append(" = ").append("? ");
              if (i != size - 1) {
                  sql.append(separator);
              }
          }
      }
  
      /**
       * 针对DRDS改造, 在 update set 集合中, 排除 单个拆分键 的赋值操作
       * @param sql
       * @param columns
       * @param separator
       * @param excludeShardColumn 需要排除的 拆分列
       */
      protected void appendExcludeSingleShardColumnEquals(StringBuilder sql, String[] columns, String separator, boolean updatePks, String excludeShardColumn) {
          int size = columns.length;
          for (int i = 0; i < size; i++) {
              // 如果是DRDS数据库, 并且存在拆分键 且 等于当前循环列, 跳过
              if(!updatePks && excludeShardColumn != null && columns[i].equals(excludeShardColumn)){
                  continue;
              }
              sql.append(" ").append(appendEscape(columns[i])).append(" = ").append("? ");
              if (i != size - 1) {
                  sql.append(separator);
              }
          }
      }
  }
  