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/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-

 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:

 *

 *  Copyright (C) 2008-2009 Sun Microsystems

 *

 *  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

 */

#include "config.h"

#include "drizzled/sql_base.h"

#include "drizzled/sql_select.h"

#include "drizzled/memory/sql_alloc.h"

#include "drizzled/optimizer/range.h"

#include "drizzled/optimizer/range_param.h"

#include "drizzled/optimizer/sel_arg.h"

#include "drizzled/optimizer/sel_tree.h"

#include "drizzled/optimizer/sel_imerge.h"

using namespace std;

using namespace drizzled;

static optimizer::SEL_ARG *key_or(optimizer::RangeParameter *param, optimizer::SEL_ARG *key1, optimizer::SEL_ARG *key2);

static bool eq_tree(optimizer::SEL_ARG* a, optimizer::SEL_ARG *b);

bool optimizer::sel_trees_can_be_ored(optimizer::SEL_TREE *tree1, 

                                      optimizer::SEL_TREE *tree2,

                                      optimizer::RangeParameter* param)

{

  key_map common_keys= tree1->keys_map;

  common_keys&= tree2->keys_map;

  if (common_keys.none())

  {

    return false;

  }

  /* trees have a common key, check if they refer to same key part */

  optimizer::SEL_ARG **key1,**key2;

  for (uint32_t key_no=0; key_no < param->keys; key_no++)

  {

    if (common_keys.test(key_no))

    {

      key1= tree1->keys + key_no;

      key2= tree2->keys + key_no;

      if ((*key1)->part == (*key2)->part)

      {

        return true;

      }

    }

  }

  return false;

}

/*

  Perform OR operation on 2 index_merge lists, storing result in first list.

  NOTES

    The following conversion is implemented:

     (a_1 &&...&& a_N)||(b_1 &&...&& b_K) = AND_i,j(a_i || b_j) =>

      => (a_1||b_1).

    i.e. all conjuncts except the first one are currently dropped.

    This is done to avoid producing N*K ways to do index_merge.

    If (a_1||b_1) produce a condition that is always true, NULL is returned

    and index_merge is discarded (while it is actually possible to try

    harder).

    As a consequence of this, choice of keys to do index_merge read may depend

    on the order of conditions in WHERE part of the query.

  RETURN

    0     OK, result is stored in *im1

    other Error, both passed lists are unusable

*/

static int imerge_list_or_list(optimizer::RangeParameter *param,

                               List<optimizer::SEL_IMERGE> *im1,

                               List<optimizer::SEL_IMERGE> *im2)

{

  optimizer::SEL_IMERGE *imerge= im1->head();

  im1->empty();

  im1->push_back(imerge);

  return imerge->or_sel_imerge_with_checks(param, im2->head());

}

/*

  Perform OR operation on index_merge list and key tree.

  RETURN

     0     OK, result is stored in *im1.

     other Error

 */

static int imerge_list_or_tree(optimizer::RangeParameter *param,

                               List<optimizer::SEL_IMERGE> *im1,

                               optimizer::SEL_TREE *tree)

{

  optimizer::SEL_IMERGE *imerge= NULL;

  List_iterator<optimizer::SEL_IMERGE> it(*im1);

  while ((imerge= it++))

  {

    if (imerge->or_sel_tree_with_checks(param, tree))

      it.remove();

  }

  return im1->is_empty();

}

optimizer::SEL_TREE *

optimizer::tree_or(optimizer::RangeParameter *param,

                   optimizer::SEL_TREE *tree1,

                   optimizer::SEL_TREE *tree2)

{

  if (! tree1 || ! tree2)

  {

    return 0;

  }

  if (tree1->type == optimizer::SEL_TREE::IMPOSSIBLE || tree2->type == optimizer::SEL_TREE::ALWAYS)

  {

    return tree2;

  }

  if (tree2->type == optimizer::SEL_TREE::IMPOSSIBLE || tree1->type == optimizer::SEL_TREE::ALWAYS)

  {

    return tree1;

  }

  if (tree1->type == optimizer::SEL_TREE::MAYBE)

  {

    return tree1; // Can't use this

  }

  if (tree2->type == optimizer::SEL_TREE::MAYBE)

  {

    return tree2;

  }

  optimizer::SEL_TREE *result= NULL;

  key_map  result_keys;

  result_keys.reset();

  if (sel_trees_can_be_ored(tree1, tree2, param))

  {

    /* Join the trees key per key */

    optimizer::SEL_ARG **key1= NULL;

    optimizer::SEL_ARG **key2= NULL;

    optimizer::SEL_ARG **end= NULL;

    for (key1= tree1->keys,key2= tree2->keys,end= key1+param->keys;

         key1 != end; 

         key1++, key2++)

    {

      *key1= key_or(param, *key1, *key2);

      if (*key1)

      {

        result= tree1; // Added to tree1

        result_keys.set(key1 - tree1->keys);

      }

    }

    if (result)

      result->keys_map= result_keys;

  }

  else

  {

    /* ok, two trees have KEY type but cannot be used without index merge */

    if (tree1->merges.is_empty() && tree2->merges.is_empty())

    {

      if (param->remove_jump_scans)

      {

        bool no_trees= optimizer::remove_nonrange_trees(param, tree1);

        no_trees= no_trees || optimizer::remove_nonrange_trees(param, tree2);

        if (no_trees)

        {

          return (new optimizer::SEL_TREE(optimizer::SEL_TREE::ALWAYS));

        }

      }

      optimizer::SEL_IMERGE *merge= NULL;

      /* both trees are "range" trees, produce new index merge structure */

      if (! (result= new optimizer::SEL_TREE()) || 

          ! (merge= new optimizer::SEL_IMERGE()) ||

          (result->merges.push_back(merge)) ||

          (merge->or_sel_tree(param, tree1)) ||

          (merge->or_sel_tree(param, tree2)))

      {

        result= NULL;

      }

      else

      {

        result->type= tree1->type;

      }

    }

    else if (!tree1->merges.is_empty() && !tree2->merges.is_empty())

    {

      if (imerge_list_or_list(param, &tree1->merges, &tree2->merges))

        result= new optimizer::SEL_TREE(optimizer::SEL_TREE::ALWAYS);

      else

        result= tree1;

    }

    else

    {

      /* one tree is index merge tree and another is range tree */

      if (tree1->merges.is_empty())

        std::swap(tree1, tree2);

      if (param->remove_jump_scans && optimizer::remove_nonrange_trees(param, tree2))

         return(new optimizer::SEL_TREE(optimizer::SEL_TREE::ALWAYS));

      /* add tree2 to tree1->merges, checking if it collapses to ALWAYS */

      if (imerge_list_or_tree(param, &tree1->merges, tree2))

        result= new optimizer::SEL_TREE(optimizer::SEL_TREE::ALWAYS);

      else

        result= tree1;

    }

  }

  return result;

}

static optimizer::SEL_ARG *

key_or(optimizer::RangeParameter *param, optimizer::SEL_ARG *key1, optimizer::SEL_ARG *key2)

{

  if (! key1)

  {

    if (key2)

    {

      key2->use_count--;

      key2->free_tree();

    }

    return 0;

  }

  if (! key2)

  {

    key1->use_count--;

    key1->free_tree();

    return 0;

  }

  key1->use_count--;

  key2->use_count--;

  if (key1->part != key2->part)

  {

    key1->free_tree();

    key2->free_tree();

    return 0;					// Can't optimize this

  }

  // If one of the key is MAYBE_KEY then the found region may be bigger

  if (key1->type == optimizer::SEL_ARG::MAYBE_KEY)

  {

    key2->free_tree();

    key1->use_count++;

    return key1;

  }

  if (key2->type == optimizer::SEL_ARG::MAYBE_KEY)

  {

    key1->free_tree();

    key2->use_count++;

    return key2;

  }

  if (key1->use_count > 0)

  {

    if (key2->use_count == 0 || key1->elements > key2->elements)

    {

      std::swap(key1,key2);

    }

    if (key1->use_count > 0 || !(key1=key1->clone_tree(param)))

      return 0;					// OOM

  }

  // Add tree at key2 to tree at key1

  bool key2_shared= key2->use_count != 0;

  key1->maybe_flag|= key2->maybe_flag;

  for (key2=key2->first(); key2; )

  {

    optimizer::SEL_ARG *tmp= key1->find_range(key2); // Find key1.min <= key2.min

    int cmp;

    if (! tmp)

    {

      tmp=key1->first(); // tmp.min > key2.min

      cmp= -1;

    }

    else if ((cmp=tmp->cmp_max_to_min(key2)) < 0)

    {						// Found tmp.max < key2.min

      optimizer::SEL_ARG *next= tmp->next;

      if (cmp == -2 && eq_tree(tmp->next_key_part,key2->next_key_part))

      {

        // Join near ranges like tmp.max < 0 and key2.min >= 0

        optimizer::SEL_ARG *key2_next=key2->next;

        if (key2_shared)

        {

          if (! (key2=new optimizer::SEL_ARG(*key2)))

            return 0;		// out of memory

          key2->increment_use_count(key1->use_count+1);

          key2->next= key2_next; // New copy of key2

        }

        key2->copy_min(tmp);

        if (! (key1=key1->tree_delete(tmp)))

        {					// Only one key in tree

          key1= key2;

          key1->make_root();

          key2= key2_next;

          break;

        }

      }

      if (! (tmp= next)) // tmp.min > key2.min

        break; // Copy rest of key2

    }

    if (cmp < 0)

    {						// tmp.min > key2.min

      int tmp_cmp;

      if ((tmp_cmp= tmp->cmp_min_to_max(key2)) > 0) // if tmp.min > key2.max

      {

        if (tmp_cmp == 2 && eq_tree(tmp->next_key_part,key2->next_key_part))

        {					// ranges are connected

          tmp->copy_min_to_min(key2);

          key1->merge_flags(key2);

          if (tmp->min_flag & NO_MIN_RANGE &&

              tmp->max_flag & NO_MAX_RANGE)

          {

            if (key1->maybe_flag)

              return new optimizer::SEL_ARG(optimizer::SEL_ARG::MAYBE_KEY);

            return 0;

          }

          key2->increment_use_count(-1);	// Free not used tree

          key2= key2->next;

          continue;

        }

        else

        {

          optimizer::SEL_ARG *next= key2->next; // Keys are not overlapping

          if (key2_shared)

          {

            optimizer::SEL_ARG *cpy= new optimizer::SEL_ARG(*key2); // Must make copy

            if (! cpy)

              return 0; // OOM

            key1= key1->insert(cpy);

            key2->increment_use_count(key1->use_count+1);

          }

          else

            key1= key1->insert(key2);		// Will destroy key2_root

          key2= next;

          continue;

        }

      }

    }

    // tmp.max >= key2.min && tmp.min <= key.cmax(overlapping ranges)

    if (eq_tree(tmp->next_key_part,key2->next_key_part))

    {

      if (tmp->is_same(key2))

      {

        tmp->merge_flags(key2);			// Copy maybe flags

        key2->increment_use_count(-1);		// Free not used tree

      }

      else

      {

        optimizer::SEL_ARG *last= tmp;

        while (last->next && last->next->cmp_min_to_max(key2) <= 0 &&

               eq_tree(last->next->next_key_part,key2->next_key_part))

        {

          optimizer::SEL_ARG *save= last;

          last= last->next;

          key1= key1->tree_delete(save);

        }

        last->copy_min(tmp);

        if (last->copy_min(key2) || last->copy_max(key2))

        {					// Full range

          key1->free_tree();

          for (; key2; key2= key2->next)

            key2->increment_use_count(-1);	// Free not used tree

          if (key1->maybe_flag)

            return new optimizer::SEL_ARG(optimizer::SEL_ARG::MAYBE_KEY);

          return 0;

        }

      }

      key2= key2->next;

      continue;

    }

    if (cmp >= 0 && tmp->cmp_min_to_min(key2) < 0)

    {						// tmp.min <= x < key2.min

      optimizer::SEL_ARG *new_arg= tmp->clone_first(key2);

      if (! new_arg)

        return 0;				// OOM

      if ((new_arg->next_key_part= key1->next_key_part))

        new_arg->increment_use_count(key1->use_count+1);

      tmp->copy_min_to_min(key2);

      key1= key1->insert(new_arg);

    }

    // tmp.min >= key2.min && tmp.min <= key2.max

    optimizer::SEL_ARG key(*key2); // Get copy we can modify

    for (;;)

    {

      if (tmp->cmp_min_to_min(&key) > 0)

      {						// key.min <= x < tmp.min

        optimizer::SEL_ARG *new_arg= key.clone_first(tmp);

        if (! new_arg)

          return 0;				// OOM

        if ((new_arg->next_key_part=key.next_key_part))

          new_arg->increment_use_count(key1->use_count+1);

        key1= key1->insert(new_arg);

      }

      if ((cmp=tmp->cmp_max_to_max(&key)) <= 0)

      {						// tmp.min. <= x <= tmp.max

        tmp->maybe_flag|= key.maybe_flag;

        key.increment_use_count(key1->use_count+1);

        tmp->next_key_part= key_or(param, tmp->next_key_part, key.next_key_part);

        if (! cmp)				// Key2 is ready

          break;

        key.copy_max_to_min(tmp);

        if (! (tmp= tmp->next))

        {

          optimizer::SEL_ARG *tmp2= new optimizer::SEL_ARG(key);

          if (! tmp2)

            return 0;				// OOM

          key1= key1->insert(tmp2);

          key2= key2->next;

          goto end;

        }

        if (tmp->cmp_min_to_max(&key) > 0)

        {

          optimizer::SEL_ARG *tmp2= new optimizer::SEL_ARG(key);

          if (! tmp2)

            return 0;				// OOM

          key1= key1->insert(tmp2);

          break;

        }

      }

      else

      {

        optimizer::SEL_ARG *new_arg= tmp->clone_last(&key); // tmp.min <= x <= key.max

        if (! new_arg)

          return 0;				// OOM

        tmp->copy_max_to_min(&key);

        tmp->increment_use_count(key1->use_count+1);

        /* Increment key count as it may be used for next loop */

        key.increment_use_count(1);

        new_arg->next_key_part= key_or(param, tmp->next_key_part, key.next_key_part);

        key1= key1->insert(new_arg);

        break;

      }

    }

    key2= key2->next;

  }

end:

  while (key2)

  {

    optimizer::SEL_ARG *next= key2->next;

    if (key2_shared)

    {

      optimizer::SEL_ARG *tmp= new optimizer::SEL_ARG(*key2);		// Must make copy

      if (! tmp)

        return 0;

      key2->increment_use_count(key1->use_count+1);

      key1= key1->insert(tmp);

    }

    else

      key1= key1->insert(key2);			// Will destroy key2_root

    key2= next;

  }

  key1->use_count++;

  return key1;

}

/*

  Remove the trees that are not suitable for record retrieval.

  SYNOPSIS

    param  Range analysis parameter

    tree   Tree to be processed, tree->type is KEY or KEY_SMALLER

  DESCRIPTION

    This function walks through tree->keys[] and removes the SEL_ARG* trees

    that are not "maybe" trees (*) and cannot be used to construct quick range

    selects.

    (*) - have type MAYBE or MAYBE_KEY. Perhaps we should remove trees of

          these types here as well.

    A SEL_ARG* tree cannot be used to construct quick select if it has

    tree->part != 0. (e.g. it could represent "keypart2 < const").

    WHY THIS FUNCTION IS NEEDED

    Normally we allow construction of optimizer::SEL_TREE objects that have SEL_ARG

    trees that do not allow quick range select construction. For example for

    " keypart1=1 AND keypart2=2 " the execution will proceed as follows:

    tree1= optimizer::SEL_TREE { SEL_ARG{keypart1=1} }

    tree2= optimizer::SEL_TREE { SEL_ARG{keypart2=2} } -- can't make quick range select

                                               from this

    call tree_and(tree1, tree2) -- this joins SEL_ARGs into a usable SEL_ARG

                                   tree.

    There is an exception though: when we construct index_merge optimizer::SEL_TREE,

    any SEL_ARG* tree that cannot be used to construct quick range select can

    be removed, because current range analysis code doesn't provide any way

    that tree could be later combined with another tree.

    Consider an example: we should not construct

    st1 = optimizer::SEL_TREE {

      merges = SEL_IMERGE {

                            optimizer::SEL_TREE(t.key1part1 = 1),

                            optimizer::SEL_TREE(t.key2part2 = 2)   -- (*)

                          }

                   };

    because

     - (*) cannot be used to construct quick range select,

     - There is no execution path that would cause (*) to be converted to

       a tree that could be used.

    The latter is easy to verify: first, notice that the only way to convert

    (*) into a usable tree is to call tree_and(something, (*)).

    Second look at what tree_and/tree_or function would do when passed a

    optimizer::SEL_TREE that has the structure like st1 tree has, and conlcude that

    tree_and(something, (*)) will not be called.

  RETURN

    0  Ok, some suitable trees left

    1  No tree->keys[] left.

*/

bool optimizer::remove_nonrange_trees(optimizer::RangeParameter *param, optimizer::SEL_TREE *tree)

{

  bool res= false;

  for (uint32_t i= 0; i < param->keys; i++)

  {

    if (tree->keys[i])

    {

      if (tree->keys[i]->part)

      {

        tree->keys[i]= NULL;

        tree->keys_map.reset(i);

      }

      else

        res= true;

    }

  }

  return ! res;

}

/* Compare if two trees are equal */

static bool eq_tree(optimizer::SEL_ARG *a, optimizer::SEL_ARG *b)

{

  if (a == b)

  {

    return true;

  }

  if (! a || ! b || ! a->is_same(b))

  {

    return false;

  }

  if (a->left != &optimizer::null_element && b->left != &optimizer::null_element)

  {

    if (! eq_tree(a->left,b->left))

      return false;

  }

  else if (a->left != &optimizer::null_element || b->left != &optimizer::null_element)

  {

    return false;

  }

  if (a->right != &optimizer::null_element && b->right != &optimizer::null_element)

  {

    if (! eq_tree(a->right,b->right))

      return false;

  }

  else if (a->right != &optimizer::null_element || b->right != &optimizer::null_element)

  {

    return false;

  }

  if (a->next_key_part != b->next_key_part)

  {						// Sub range

    if (! a->next_key_part != ! b->next_key_part ||

	      ! eq_tree(a->next_key_part, b->next_key_part))

      return false;

  }

  return true;

}