UnorderedRowStructure.java

/*
** Module   : UnorderedRowStructure.java
** Abstract : Defines a row structure in a query. This time, the fields can have an arbitrary order.
**
** Copyright (c) 2023, Golden Code Development Corporation.
**
** -#- -I- --Date-- ----------------------------------------Description---------------------------------------
** 001 AL2 20231128 Initial version.
**     AL2 20231212 Use dmoMeta directly, without getter.
*/

/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
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**   terms apply to the works covered under the License.  These additional terms
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*/

package com.goldencode.p2j.persist.orm;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.*;

import com.goldencode.p2j.persist.*;

/**
 * Slowest kind of row structure that is able to hdyrate fields in an arbitrary order.
 * This is not necessary a bottle-neck, but is uses a list instead of a faster data structure,
 * like Bitset. This kind of structure shouldn't be necessarily used internally by FWD, as we
 * can earlier detect if we actually need other faster implementations. This kind of unordered
 * structure is more useful to code that uses the low-level layers of FWD.
 */
public class UnorderedRowStructure
extends AbstractRowStructure
{
   /** 
    * The fields that should be hydrated. This stores only their ids in the data array.
    * For recid and multiplex, we use special markers.
    */
   public final List<Integer> fields;
   
   /** A cached value of the property meta array that can be found in the record meta */
   private final PropertyMeta[] pm;
   
   /** The number of SQL columns that can be hydrated using this structure. */
   private int count;
   
   /**
    * Create a new instance.
    * 
    * @param    meta
    *           The DMO metadata of the underlying DMO for this structure.
    */
   public UnorderedRowStructure(DmoMeta meta)
   {
      super(meta);
      this.fields = new ArrayList<>();
      this.pm = dmoMeta.recordMeta.getPropertyMeta(false);
      this.count = 0;
   }

   /**
    * Append the recid to the row structure.
    * 
    * @param   recid 
    *          The recid property to be appended to the structure.
    * 
    * @return  {@code true} if adding the recid to the row structure succeeded
    *          If there is some invariant on the structure, adding props may fail.
    */
   @Override
   public boolean addRecid(Property recid)
   {
      fields.add(ReservedProperty.ID_PRIMARY_KEY);
      count++;
      return true;
   }

   /**
    * Append the multiplex to the row structure.
    * 
    * @param   multiplex 
    *          The multiplex property to be appended to the structure.
    * 
    * @return  {@code true} if adding the multiplex to the row structure succeeded
    *          If there is some invariant on the structure, adding props may fail.
    */
   @Override
   public boolean addMultiplex(Property multiplex)
   {
      fields.add(ReservedProperty.ID_MULTIPLEX);
      count++;
      return true;
   }
   
   /**
    * Append a property to the row structure. This doesn't check if the property actually belongs to the
    * DMO class used for this structure.
    * 
    * @param   prop 
    *          The property to be appended to the structure.
    * 
    * @return  {@code true} if adding the prop to the row structure succeeded
    *          If there is some invariant on the structure, adding props may fail.
    */
   @Override
   public boolean addProperty(Property prop)
   {
      if (super.addProperty(prop))
      {
         // skip non-expanded extent fields; they will be hydrated by super at the end
         return true;
      }
      
      int idx = dmoMeta.recordMeta.getIndexOfProperty(prop.name);
      fields.add(idx);
      count += pm[idx].columnCount;
      return true;
   }

   /**
    * Retrieve the number of SQL fields that will be interpreted by this row structure. This is not the
    * same as the number of properties (e.g. datetime-tz consumes 2 SQL columns) 
    * 
    * @return   The number of SQL fields that are covered by this row structure.
    */
   @Override
   public int getCount()
   {
      return this.count;
   }

   /**
    * Retrieve an iterator to all properties in this structure, including the recid and multiplex.
    * 
    * @return   An iterator to all properties in this structure, in order of their append.
    */
   @Override
   public Iterator<Property> getProps()
   {
      return new Iterator<Property>() 
      {
         private int idx = 0;

         @Override
         public boolean hasNext()
         {
            return idx < fields.size();
         }

         @Override
         public Property next()
         {
            if (!hasNext())
            {
               throw new NoSuchElementException();
            }
            
            return pm[fields.get(idx++)].dmoProperty;
         }
         
      };
   }

   /**
    * Hydrate a record knowing that the result-set selected some properties in arbitrary order.
    * Never presume an implicit order of the properties in the result-set when using such row
    * structure. Always presume that there will be only some poperties whose index in the 
    * record should be determined. 
    * 
    * @param   session 
    *          The underlying session that generated the result-set. It is used only to emit
    *          load SQLs for the non-expanded extents. If this is {@code null}, the non-expanded
    *          extents will be skipped.
    * @param   resultSet
    *          The result-set that provides the low-level data that should be hydrated into
    *          the record.
    * @param   rsOffset
    *          The offset where the DMO starts. This is the case for queries that had joins,
    *          so the current record may not start at index 1.
    * @param   r
    *          The record to be hydrated.
    *          
    * @return  The next rsOffset, from where the next DMO in the result-set will start (if any).
    * 
    * @throws  PersistenceException
    *          thrown when hydrating extents fails (as it requires extra SQL queries to be run).
    * @throws  SQLException
    *          throw when failing to hydrate from the result-set.   
    */
   @Override
   public int hydrate(Session session, ResultSet resultSet, int rsOffset, BaseRecord r)
   throws PersistenceException,
          SQLException
   {
      int fieldCnt = fields.size();
      for (int i = 0; i < fieldCnt; i++)
      {
         int idx = fields.get(i);
         
         if (idx == ReservedProperty.ID_PRIMARY_KEY)
         {
            r.primaryKey(resultSet.getLong(rsOffset++));
            if (fieldCnt == 1)
            {
               return rsOffset;
            }
         }
         else if (idx == ReservedProperty.ID_MULTIPLEX)
         {
            ((TempRecord) r)._multiplex(resultSet.getInt(rsOffset++));
         }
         else
         {
            rsOffset += r.readProperty(idx, resultSet, rsOffset);
         }
      }
      
      if (hasExtents && session != null)
      {
         hydrateExtents(session, r, -1);
      }
      
      return rsOffset;
   }
}