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  package org.apache.cayenne.access.translator.select;
  
  import java.sql.Types;
  
  /**
   * @since 4.2
   */
  class DistinctStage implements TranslationStage {
  
      private static final int[] UNSUPPORTED_DISTINCT_TYPES = {
              Types.BLOB,
              Types.CLOB,
              Types.NCLOB,
              Types.LONGVARCHAR,
              Types.LONGNVARCHAR,
              Types.LONGVARBINARY
      };
  
      static boolean isUnsupportedForDistinct(int type) {
          for (int unsupportedDistinctType : UNSUPPORTED_DISTINCT_TYPES) {
              if (unsupportedDistinctType == type) {
                  return true;
              }
          }
  
          return false;
      }
  
      @Override
      public void perform(TranslatorContext context) {
          // explicit suppressing of distinct
          if(context.getMetadata().isSuppressingDistinct()) {
              context.setDistinctSuppression(true);
              return;
          }
  
          // query forcing distinct or query have joins (qualifier or prefetch)
          if(!context.getQuery().isDistinct() && !context.getTableTree().hasToManyJoin()) {
              return;
          }
  
          // unsuitable jdbc type for distinct clause
          for(ResultNodeDescriptor node : context.getResultNodeList()) {
              // TODO: make it per adapter rather than one-for-all
              if(isUnsupportedForDistinct(node.getJdbcType())) {
                  context.setDistinctSuppression(true);
                  return;
              }
          }
          context.getSelectBuilder().distinct();
      }
  }
  