/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
 *
 *  Copyright (C) 2009 Sun Microsystems, Inc.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; version 2 of the License.
 *
 *  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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#ifndef DRIZZLED_OPTIMIZER_KEY_FIELD_H
#define DRIZZLED_OPTIMIZER_KEY_FIELD_H

#include <drizzled/sql_select.h>

#include <vector>

namespace drizzled
{
namespace optimizer
{

/**
 * Class used when finding key fields
 */
class KeyField
{
public:

  KeyField()
    :
      field(NULL),
      val(NULL),
      level(0),
      optimize(0),
      eq_func(false),
      null_rejecting(false),
      cond_guard(NULL)
  {}

  KeyField(Field *in_field,
           Item *in_val,
           uint32_t in_level,
           uint32_t in_optimize,
           bool in_eq_func,
           bool in_null_rejecting,
           bool *in_cond_guard)
    :
      field(in_field),
      val(in_val),
      level(in_level),
      optimize(in_optimize),
      eq_func(in_eq_func),
      null_rejecting(in_null_rejecting),
      cond_guard(in_cond_guard)
  {}

  Field *getField()
  {
    return field;
  }

  void setField(Field *in_field)
  {
    field= in_field;
  }

  Item *getValue()
  {
    return val;
  }

  void setValue(Item *in_val)
  {
    val= in_val;
  }

  uint32_t getLevel()
  {
    return level;
  }

  void setLevel(uint32_t in_level)
  {
    level= in_level;
  }

  uint32_t getOptimizeFlags()
  {
    return optimize;
  }

  void setOptimizeFlags(uint32_t in_opt)
  {
    optimize= in_opt;
  }

  bool isEqualityCondition() const
  {
    return eq_func;
  }

  void setEqualityConditionUsed(bool in_val)
  {
    eq_func= in_val;
  }

  bool rejectNullValues() const
  {
    return null_rejecting;
  }

  void setRejectNullValues(bool in_val)
  {
    null_rejecting= in_val;
  }

  bool *getConditionalGuard()
  {
    return cond_guard;
  }

  void setConditionalGuard(bool *in_cond_guard)
  {
    cond_guard= in_cond_guard;
  }

private:

  Field *field;
  Item *val; /**< May be empty if diff constant */
  uint32_t level;
  uint32_t optimize; /**< KEY_OPTIMIZE_* */
  bool eq_func;
  /**
    If true, the condition this class represents will not be satisfied
    when val IS NULL.
  */
  bool null_rejecting;
  bool *cond_guard; /**< @see KeyUse::cond_guard */

};

void add_key_fields(Join *join, 
                    KeyField **key_fields,
                    uint32_t *and_level,
                    COND *cond,
                    table_map usable_tables,
                    std::vector<SargableParam> &sargables);

void add_key_part(DYNAMIC_ARRAY *keyuse_array, KeyField *key_field);

/**
 * Add to KeyField array all 'ref' access candidates within nested join.
 *
 * This function populates KeyField array with entries generated from the
 * ON condition of the given nested join, and does the same for nested joins
 * contained within this nested join.
 *
 * @param[in]      nested_join_table   Nested join pseudo-table to process
 * @param[in,out]  end                 End of the key field array
 * @param[in,out]  and_level           And-level
 * @param[in,out]  sargables           std::vector of found sargable candidates
 *
 *
 * @note
 *   We can add accesses to the tables that are direct children of this nested
 *   join (1), and are not inner tables w.r.t their neighbours (2).
 *
 *   Example for #1 (outer brackets pair denotes nested join this function is
 *   invoked for):
 *   @code
 *    ... LEFT JOIN (t1 LEFT JOIN (t2 ... ) ) ON cond
 *   @endcode
 *   Example for #2:
 *   @code
 *    ... LEFT JOIN (t1 LEFT JOIN t2 ) ON cond
 *   @endcode
 *   In examples 1-2 for condition cond, we can add 'ref' access candidates to
 *   t1 only.
 *   Example #3:
 *   @code
 *    ... LEFT JOIN (t1, t2 LEFT JOIN t3 ON inner_cond) ON cond
 *   @endcode
 *   Here we can add 'ref' access candidates for t1 and t2, but not for t3.
 */
void add_key_fields_for_nj(Join *join,
                           TableList *nested_join_table,
                           KeyField **end,
                           uint32_t *and_level,
                           std::vector<SargableParam> &sargables);

/**
 * Merge new key definitions to old ones, remove those not used in both.
 *
 * This is called for OR between different levels.
 *
 * To be able to do 'ref_or_null' we merge a comparison of a column
 * and 'column IS NULL' to one test.  This is useful for sub select queries
 * that are internally transformed to something like:.
 *
 * @code
 * SELECT * FROM t1 WHERE t1.key=outer_ref_field or t1.key IS NULL
 * @endcode
 *
 * KeyField::null_rejecting is processed as follows: @n
 * result has null_rejecting=true if it is set for both ORed references.
 * for example:
 * -   (t2.key = t1.field OR t2.key  =  t1.field) -> null_rejecting=true
 * -   (t2.key = t1.field OR t2.key <=> t1.field) -> null_rejecting=false
 *
 * @todo
 *   The result of this is that we're missing some 'ref' accesses.
 *   OptimizerTeam: Fix this
 */
KeyField *merge_key_fields(KeyField *start,
                            KeyField *new_fields,
                            KeyField *end, 
                            uint32_t and_level);

/**
 * Add a possible key to array of possible keys if it's usable as a key
 *
 * @param key_fields      Pointer to add key, if usable
 * @param and_level       And level, to be stored in KeyField
 * @param cond            Condition predicate
 * @param field           Field used in comparision
 * @param eq_func         True if we used =, <=> or IS NULL
 * @param value           Value used for comparison with field
 * @param usable_tables   Tables which can be used for key optimization
 * @param sargables       IN/OUT std::vector of found sargable candidates
 *
 * @note
 *  If we are doing a NOT NULL comparison on a NOT NULL field in a outer join
 *  table, we store this to be able to do not exists optimization later.
 *
 * @returns
 *  *key_fields is incremented if we stored a key in the array
 */
void add_key_field(KeyField **key_fields,
                   uint32_t and_level,
                   Item_func *cond,
                   Field *field,
                   bool eq_func,
                   Item **value,
                   uint32_t num_values,
                   table_map usable_tables,
                   std::vector<SargableParam> &sargables);

/**
 * Add possible keys to array of possible keys originated from a simple
 * predicate.
 *
 * @param  key_fields     Pointer to add key, if usable
 * @param  and_level      And level, to be stored in KeyField
 * @param  cond           Condition predicate
 * @param  field          Field used in comparision
 * @param  eq_func        True if we used =, <=> or IS NULL
 * @param  value          Value used for comparison with field
 *                        Is NULL for BETWEEN and IN
 * @param  usable_tables  Tables which can be used for key optimization
 * @param  sargables      IN/OUT std::vector of found sargable candidates
 *
 * @note
 *  If field items f1 and f2 belong to the same multiple equality and
 *  a key is added for f1, the the same key is added for f2.
 *
 * @returns
 *  *key_fields is incremented if we stored a key in the array
*/
void add_key_equal_fields(KeyField **key_fields,
                          uint32_t and_level,
                          Item_func *cond,
                          Item_field *field_item,
                          bool eq_func,
                          Item **val,
                          uint32_t num_values,
                          table_map usable_tables,
                          std::vector<SargableParam> &sargables);

} /* end namespace optimizer */

} /* end namespace drizzled */

#endif /* DRIZZLED_OPTIMIZER_KEY_FIELD_H */
