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From:Ole John Aske Date:January 5 2012 2:41pm
Subject:bzr push into mysql-trunk branch (ole.john.aske:3705 to 3706) WL#5940
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 3706 Ole John Aske	2012-01-05
      (Re)Commit of the patches for wl#5940 into the branch mysql-trunk-wl5940_2
      
      Patches has been rebased to refactored version of optimizer.
      It has also been simplifed under the assumption that wl5558
      and it's family of related fixes has been implemented as a basis for 
      these patches.
      
      (WL5558: Resolve ORDER BY execution method at the optimization stage.)

    added:
      sql/abstract_query_plan.cc
      sql/abstract_query_plan.h
    modified:
      sql/CMakeLists.txt
      sql/handler.cc
      sql/handler.h
      sql/opt_explain.cc
      sql/sql_executor.cc
      sql/sql_optimizer.cc
 3705 Ole John Aske	2012-01-05
      Establish new baseline branch for WL#5940 review: mysqltrunk-wl5949_2:
      
      - There has been lots of refactoring in the optimizer since the original WL5940
        branch was created. We need to refactor the WL5940 patches to due to this.
      
      - One of the inital comments from Evgeny suggested that WL5940 would be cleaner
        if the Abstract Query Plan didn't have to call test_if_skip_sort_order(). Which
        had the sideffect that the query plan could be changed. This required us
        to implement WL5558 first, and then base a simpler wl5940 on this.
      
      This commit add proposed implementation for WL5558 to mysql-trunk and 
      the bugfixes it depends on - Look in wl5558 for a description of these.

    modified:
      mysql-test/include/icp_tests.inc
      mysql-test/include/order_by.inc
      mysql-test/r/group_by.result
      mysql-test/r/group_min_max.result
      mysql-test/r/innodb_icp.result
      mysql-test/r/innodb_icp_none.result
      mysql-test/r/innodb_mrr.result
      mysql-test/r/innodb_mrr_cost.result
      mysql-test/r/innodb_mrr_cost_icp.result
      mysql-test/r/innodb_mrr_icp.result
      mysql-test/r/innodb_mrr_none.result
      mysql-test/r/join_cache_bka.result
      mysql-test/r/join_cache_bka_nixbnl.result
      mysql-test/r/join_cache_bkaunique.result
      mysql-test/r/join_cache_bnl.result
      mysql-test/r/join_cache_nojb.result
      mysql-test/r/myisam_icp.result
      mysql-test/r/myisam_icp_none.result
      mysql-test/r/order_by_icp_mrr.result
      mysql-test/r/order_by_none.result
      mysql-test/r/select_found.result
      mysql-test/r/subquery_mat_none.result
      mysql-test/suite/opt_trace/r/bugs_no_prot_none.result
      mysql-test/suite/opt_trace/r/range_no_prot.result
      sql/opt_range.cc
      sql/records.cc
      sql/sql_executor.cc
      sql/sql_optimizer.cc
      sql/sql_optimizer.h
      sql/sql_select.cc
=== modified file 'sql/CMakeLists.txt'
--- a/sql/CMakeLists.txt	2011-12-15 17:14:28 +0000
+++ b/sql/CMakeLists.txt	2012-01-05 14:41:08 +0000
@@ -37,6 +37,7 @@ IF(SSL_DEFINES)
 ENDIF()
 
 SET(SQL_SHARED_SOURCES
+  abstract_query_plan.cc
   datadict.cc
   debug_sync.cc
   derror.cc

=== added file 'sql/abstract_query_plan.cc'
--- a/sql/abstract_query_plan.cc	1970-01-01 00:00:00 +0000
+++ b/sql/abstract_query_plan.cc	2012-01-05 14:41:08 +0000
@@ -0,0 +1,519 @@
+/*
+   Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
+
+   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 "sql_priv.h"
+#include "sql_select.h"
+#include "sql_optimizer.h"
+#include "abstract_query_plan.h"
+
+
+namespace AQP
+{
+
+  /**
+    @param join_tab Array of access methods constituting the nested loop join.
+    @param access_count Length of array.
+  */
+  Join_plan::Join_plan(const JOIN* join)
+   : m_join_tabs(join->join_tab),
+     m_access_count(join->tables),
+     m_table_accesses(NULL)
+  {
+    /*
+      This combination is assumed not to appear. If it does, code must
+      be written to handle it.
+    */
+    DBUG_ASSERT((m_join_tabs[0].use_quick != 2)
+                || (m_join_tabs[0].type == JT_ALL)
+                || (m_join_tabs[0].select == NULL)
+                || (m_join_tabs[0].select->quick == NULL));
+
+    m_table_accesses= new Table_access[m_access_count];
+    for(uint i= 0; i < m_access_count; i++)
+    {
+      m_table_accesses[i].m_join_plan= this; 
+      m_table_accesses[i].m_tab_no= i;
+    }
+  }
+
+  Join_plan::~Join_plan()
+  {
+    delete[] m_table_accesses;
+    m_table_accesses= NULL;
+  }
+
+  /** Get the JOIN_TAB of the n'th table access operation.*/
+  const JOIN_TAB* Join_plan::get_join_tab(uint join_tab_no) const
+  {
+    DBUG_ASSERT(join_tab_no < m_access_count);
+    return m_join_tabs + join_tab_no;
+  }
+
+  bool
+  Join_plan::group_by_filesort_is_skippable() const
+  {
+    const JOIN* const join= m_join_tabs->join;
+    return (join->group_list && join->simple_group && 
+            join->ordered_index_usage==JOIN::ordered_index_group_by);
+  }
+
+  bool
+  Join_plan::order_by_filesort_is_skippable() const
+  {
+    const JOIN* const join= m_join_tabs->join;
+    return (join->order && join->simple_order && 
+            join->ordered_index_usage==JOIN::ordered_index_order_by);
+  }
+
+  /**
+    Determine join type between this table access and some other table
+    access that preceeds it in the join plan..
+  */
+  enum_join_type 
+  Table_access::get_join_type(const Table_access* predecessor) const
+  {
+    DBUG_ENTER("get_join_type");
+    DBUG_ASSERT(get_access_no() > predecessor->get_access_no());
+
+    if (get_join_tab()->table->pos_in_table_list->outer_join != 0)
+    {
+      /*
+        This cover unnested outer joins such as 
+        'select * from t1 left join t2 on t1.attr=t1.pk'.
+       */
+      DBUG_PRINT("info", ("JT_OUTER_JOIN between %s and %s",
+                          predecessor->get_join_tab()->table->alias,
+                          get_join_tab()->table->alias));
+      DBUG_RETURN(JT_OUTER_JOIN);
+    }
+
+    const TABLE_LIST* const child_embedding= 
+      get_join_tab()->table->pos_in_table_list->embedding;
+
+    if (child_embedding == NULL)
+    {
+      // 'this' is not on the inner side of any left join.
+      DBUG_PRINT("info", ("JT_INNER_JOIN between %s and %s",
+                          predecessor->get_join_tab()->table->alias,
+                          get_join_tab()->table->alias));
+      DBUG_RETURN(JT_INNER_JOIN);
+    }
+
+    DBUG_ASSERT(child_embedding->outer_join != 0);
+
+    const TABLE_LIST *predecessor_embedding= 
+      predecessor->get_join_tab()->table->pos_in_table_list->embedding;
+
+    /*
+      This covers the nested join case, i.e:
+      <table reference> LEFT JOIN (<joined table>).
+      
+      TABLE_LIST objects form a tree where TABLE_LIST::emebedding points to
+      the parent object. Now if child_embedding is non null and not an 
+      ancestor of predecessor_embedding in the embedding tree, then 'this'
+      must be on the inner side of some left join where 'predecessor' is on 
+      the outer side.
+     */
+    while (true)
+    {
+      if (predecessor_embedding == child_embedding)
+      {
+        DBUG_PRINT("info", ("JT_INNER_JOIN between %s and %s",
+                            predecessor->get_join_tab()->table->alias,
+                            get_join_tab()->table->alias));
+        DBUG_RETURN(JT_INNER_JOIN);
+      }
+      else if (predecessor_embedding == NULL)
+      {
+        /*
+           We reached the root of the tree without finding child_embedding,
+           so it must be in another branch and hence on the inner side of some
+           left join where 'predecessor' is on the outer side.
+         */
+        DBUG_PRINT("info", ("JT_OUTER_JOIN between %s and %s",
+                            predecessor->get_join_tab()->table->alias,
+                            get_join_tab()->table->alias));
+        DBUG_RETURN(JT_OUTER_JOIN);
+      }
+      // Iterate through ancestors of predecessor_embedding.
+      predecessor_embedding = predecessor_embedding->embedding;
+    }
+  }
+
+  /**
+    Get the number of key values for this operation. It is an error
+    to call this method on an operation that is not an index lookup
+    operation.
+  */
+  uint Table_access::get_no_of_key_fields() const
+  {
+    DBUG_ASSERT(m_access_type == AT_PRIMARY_KEY ||
+                m_access_type == AT_UNIQUE_KEY ||
+                m_access_type == AT_MULTI_PRIMARY_KEY ||
+                m_access_type == AT_MULTI_UNIQUE_KEY ||
+                m_access_type == AT_ORDERED_INDEX_SCAN); // Used as 'range scan'
+    return get_join_tab()->ref.key_parts;
+  }
+
+  /**
+    Get the field_no'th key values for this operation. It is an error
+    to call this method on an operation that is not an index lookup
+    operation.
+  */
+  const Item* Table_access::get_key_field(uint field_no) const
+  {
+    DBUG_ASSERT(field_no < get_no_of_key_fields());
+    return get_join_tab()->ref.items[field_no];
+  }
+
+  /**
+    Get the field_no'th KEY_PART_INFO for this operation. It is an error
+    to call this method on an operation that is not an index lookup
+    operation.
+  */
+  const KEY_PART_INFO* Table_access::get_key_part_info(uint field_no) const
+  {
+    DBUG_ASSERT(field_no < get_no_of_key_fields());
+    const KEY* key= &get_join_tab()->table->key_info[get_join_tab()->ref.key];
+    return &key->key_part[field_no];
+  }
+
+  /**
+    Get the table that this operation accesses.
+  */
+  TABLE* Table_access::get_table() const
+  {
+    return get_join_tab()->table;
+  }
+
+  double Table_access::get_fanout() const
+  {
+    switch (get_access_type())
+    {
+      case AT_PRIMARY_KEY:
+      case AT_UNIQUE_KEY:
+        return 1.0;
+
+      case AT_ORDERED_INDEX_SCAN:
+        DBUG_ASSERT(get_join_tab()->join->best_positions[m_tab_no].records_read>0.0);
+        return get_join_tab()->join->best_positions[m_tab_no].records_read;
+
+      case AT_MULTI_PRIMARY_KEY:
+      case AT_MULTI_UNIQUE_KEY:
+      case AT_MULTI_MIXED:
+        DBUG_ASSERT(get_join_tab()->join->best_positions[m_tab_no].records_read>0.0);
+        return get_join_tab()->join->best_positions[m_tab_no].records_read;
+
+      case AT_TABLE_SCAN:
+        DBUG_ASSERT(get_join_tab()->table->file->stats.records>0.0);
+        return static_cast<double>(get_join_tab()->table->file->stats.records);
+
+      default:
+        return 99999999.0;
+    }
+  }
+
+  /** Get the JOIN_TAB object that corresponds to this operation.*/
+  const JOIN_TAB* Table_access::get_join_tab() const
+  {
+    return m_join_plan->get_join_tab(m_tab_no);
+  }
+
+  /** Get the Item_equal's set relevant for the specified 'Item_field' */
+  Item_equal*
+  Table_access::get_item_equal(const Item_field* field_item) const
+  {
+    DBUG_ASSERT(field_item->type() == Item::FIELD_ITEM);
+
+    COND_EQUAL* const cond_equal = get_join_tab()->join->cond_equal;
+    if (cond_equal!=NULL)
+    {
+      return (field_item->item_equal != NULL)
+               ? field_item->item_equal
+               : const_cast<Item_field*>(field_item)->find_item_equal(cond_equal);
+    }
+    return NULL;
+  }
+
+  /**
+    Write an entry in the trace file about the contents of this object.
+  */
+  void Table_access::dbug_print() const
+  {
+    DBUG_PRINT("info", ("type:%d", get_join_tab()->type));
+    DBUG_PRINT("info", ("ref.key:%d", get_join_tab()->ref.key));
+    DBUG_PRINT("info", ("ref.key_parts:%d", get_join_tab()->ref.key_parts));
+    DBUG_PRINT("info", ("ref.key_length:%d", get_join_tab()->ref.key_length));
+
+    DBUG_PRINT("info", ("order:%p", get_join_tab()->join->order));
+    DBUG_PRINT("info", ("skip_sort_order:%d",
+                        get_join_tab()->join->skip_sort_order));
+    DBUG_PRINT("info", ("no_order:%d", get_join_tab()->join->no_order));
+    DBUG_PRINT("info", ("simple_order:%d", get_join_tab()->join->simple_order));
+
+    DBUG_PRINT("info", ("group:%d", get_join_tab()->join->group));
+    DBUG_PRINT("info", ("group_list:%p", get_join_tab()->join->group_list));
+    DBUG_PRINT("info", ("simple_group:%d", get_join_tab()->join->simple_group));
+    DBUG_PRINT("info", ("group_optimized_away:%d",
+                        get_join_tab()->join->group_optimized_away));
+
+    DBUG_PRINT("info", ("full_join:%d", get_join_tab()->join->full_join));
+    DBUG_PRINT("info", ("need_tmp:%d", get_join_tab()->join->need_tmp));
+    DBUG_PRINT("info", ("select_distinct:%d",
+                        get_join_tab()->join->select_distinct));
+
+    DBUG_PRINT("info", ("use_quick:%d", get_join_tab()->use_quick));
+    DBUG_PRINT("info", ("index:%d", get_join_tab()->index));
+    DBUG_PRINT("info", ("quick:%p", get_join_tab()->quick));
+    DBUG_PRINT("info", ("select:%p", get_join_tab()->select));
+    if (get_join_tab()->select && get_join_tab()->select->quick)
+    {
+      DBUG_PRINT("info", ("select->quick->get_type():%d",
+                          get_join_tab()->select->quick->get_type()));
+    }
+  }
+
+
+  /**
+    Compute the access type and index (if apliccable) of this operation .
+  */
+  void Table_access::compute_type_and_index() const
+  {
+    DBUG_ENTER("Table_access::compute_type_and_index");
+    const JOIN_TAB* const join_tab= get_join_tab();
+    JOIN* const join= join_tab->join;
+
+    /**
+     * There are some JOIN arguments we don't fully understand or has 
+     * not yet invested time into exploring pushability of:
+     */
+    if (join->procedure)
+    {
+      m_access_type= AT_OTHER;
+      m_other_access_reason = 
+        "'PROCEDURE'-clause post processing cannot be pushed.";
+      DBUG_VOID_RETURN;
+    }
+    
+    if (join->group_list && !join->tmp_table_param.quick_group)
+    {
+      m_access_type= AT_OTHER;
+      m_other_access_reason = 
+        "GROUP BY cannot be done using index on grouped columns.";
+      DBUG_VOID_RETURN;
+    }
+
+    /* Tables below 'const_tables' has been const'ified, or entirely
+     * optimized away due to 'impossible WHERE/ON'
+     */
+    if (join_tab < join->join_tab+join->const_tables)
+    {
+      DBUG_PRINT("info", ("Operation %d is const-optimized.", m_tab_no));
+      m_access_type= AT_FIXED;
+      DBUG_VOID_RETURN;
+    }
+
+    /*
+      Identify the type of access operation and the index to use (if any).
+    */
+    switch (join_tab->type)
+    {
+    case JT_EQ_REF:
+    case JT_CONST:
+      m_index_no= join_tab->ref.key;
+
+      if (m_index_no == static_cast<int>(join_tab->table->s->primary_key))
+      {
+        DBUG_PRINT("info", ("Operation %d is a primary key lookup.", m_tab_no));
+        m_access_type= AT_PRIMARY_KEY;
+      }
+      else
+      {
+        DBUG_PRINT("info", ("Operation %d is a unique index lookup.",
+                            m_tab_no));
+        m_access_type= AT_UNIQUE_KEY;
+      }
+      break;
+
+    case JT_REF:
+    {
+      DBUG_ASSERT(join_tab->ref.key >= 0);
+      DBUG_ASSERT((uint)join_tab->ref.key < MAX_KEY);
+      m_index_no= join_tab->ref.key;
+
+      /*
+        All parts of a key are specified for an unique index -> access is a key lookup.
+      */
+      const KEY *key_info= join_tab->table->s->key_info;
+      if (key_info[m_index_no].key_parts == join_tab->ref.key_parts  &&
+          key_info[m_index_no].flags & HA_NOSAME)
+      {
+        m_access_type= 
+          (m_index_no == static_cast<int32>(join_tab->table->s->primary_key)) 
+              ? AT_PRIMARY_KEY
+              : AT_UNIQUE_KEY;
+        DBUG_PRINT("info", ("Operation %d is an unique key referrence.", m_tab_no));
+      }
+      else
+      {
+        DBUG_ASSERT(join_tab->ref.key_parts > 0);
+        DBUG_ASSERT(join_tab->ref.key_parts <= key_info[m_index_no].key_parts);
+        m_access_type= AT_ORDERED_INDEX_SCAN;
+        DBUG_PRINT("info", ("Operation %d is an ordered index scan.", m_tab_no));
+      }
+      break;
+    }
+    case JT_INDEX_SCAN:
+      DBUG_ASSERT(join_tab->index < MAX_KEY);
+      m_index_no=    join_tab->index;
+      m_access_type= AT_ORDERED_INDEX_SCAN;
+      DBUG_PRINT("info", ("Operation %d is an ordered index scan.", m_tab_no));
+      break;
+
+    case JT_ALL:
+      if (join_tab->use_quick == 2)
+      {
+        /*
+          use_quick == 2 means that the decision on which access method to use
+          will be taken late (as rows from the preceeding operation arrive).
+          This operation is therefor not pushable.
+        */
+        DBUG_PRINT("info",
+                   ("Operation %d has 'use_quick == 2' -> not pushable",
+                    m_tab_no));
+        m_access_type= AT_UNDECIDED;
+        m_index_no=    -1;
+      }
+      else
+      {
+        if (join_tab->select != NULL &&
+            join_tab->select->quick != NULL)
+        {
+          QUICK_SELECT_I *quick= join_tab->select->quick;
+
+          /** QUICK_SELECT results in execution of MRR (Multi Range Read).
+           *  Depending on each range, it may require execution of
+           *  either a PK-lookup or a range scan. To cover both of 
+           *  these we may need to prepare both a pushed lookup join
+           *  and a pushed range scan. Currently we handle it as
+           *  a range scan and convert e PK lookup to a (closed-) range
+           *  whenever required.
+           **/
+
+          const KEY *key_info= join_tab->table->s->key_info;
+          DBUG_EXECUTE("info", quick->dbug_dump(0, TRUE););
+
+          // Temporary assert as we are still investigation the relation between 
+          // 'quick->index == MAX_KEY' and the different quick_types
+          DBUG_ASSERT ((quick->index == MAX_KEY)  ==
+                        ((quick->get_type() == QUICK_SELECT_I::QS_TYPE_INDEX_MERGE) ||
+                         (quick->get_type() == QUICK_SELECT_I::QS_TYPE_ROR_INTERSECT) ||
+                         (quick->get_type() == QUICK_SELECT_I::QS_TYPE_ROR_UNION)));
+
+          // JT_INDEX_MERGE: We have a set of qualifying PKs as root of pushed joins
+          if (quick->index == MAX_KEY) 
+          {
+            m_index_no=    join_tab->table->s->primary_key;
+            m_access_type= AT_MULTI_PRIMARY_KEY;    // Multiple PKs are produced by merge
+          }
+
+          // Else JT_RANGE: May be both exact PK and/or index scans when sorted index available
+          else if (quick->index == join_tab->table->s->primary_key)
+          {
+            m_index_no= quick->index;
+            if (key_info[m_index_no].algorithm == HA_KEY_ALG_HASH)
+              m_access_type= AT_MULTI_PRIMARY_KEY; // MRR w/ multiple PK's
+            else
+              m_access_type= AT_MULTI_MIXED;       // MRR w/ both range and PKs
+          }
+          else
+          {
+            m_index_no= quick->index;
+            if (key_info[m_index_no].algorithm == HA_KEY_ALG_HASH)
+              m_access_type= AT_MULTI_UNIQUE_KEY; // MRR with multiple unique keys
+            else
+              m_access_type= AT_MULTI_MIXED;      // MRR w/ both range and unique keys
+          }
+        }
+        else
+        {
+          DBUG_PRINT("info", ("Operation %d is a table scan.", m_tab_no));
+          m_access_type= AT_TABLE_SCAN;
+        }
+      }
+      break;
+
+    default:
+      /*
+        Other join_types either cannot be pushed or the code analyze them is
+        not yet in place.
+      */
+      DBUG_PRINT("info",
+                 ("Operation %d has join_type %d. -> Not pushable.",
+                  m_tab_no, join_tab->type));
+      m_access_type= AT_OTHER;
+      m_index_no=    -1;
+      m_other_access_reason = "This table access method can not be pushed.";
+      break;
+    }
+    DBUG_VOID_RETURN;
+  }
+  // Table_access::compute_type_and_index()
+
+
+  Table_access::Table_access()
+    :m_join_plan(NULL),
+     m_tab_no(0),
+     m_access_type(AT_VOID),
+     m_other_access_reason(NULL),
+     m_index_no(-1)
+  {}
+
+  /**
+    @return True iff ordered index access is *required* from this operation. 
+  */
+  bool Table_access::is_fixed_ordered_index() const
+  {
+    const JOIN_TAB* const join_tab= get_join_tab();
+
+    /* For the QUICK_SELECT_I classes we can disable ordered index usage by
+     * setting 'QUICK_SELECT_I::sorted = false'.
+     * However, QUICK_SELECT_I::QS_TYPE_RANGE_DESC is special as its 
+     * internal implementation requires its 'multi-ranges' to be retrieved
+     * in (descending) sorted order from the underlying table.
+     */
+    if (join_tab->select != NULL &&
+        join_tab->select->quick != NULL)
+    {
+      QUICK_SELECT_I *quick= join_tab->select->quick;
+      return (quick->get_type() == QUICK_SELECT_I::QS_TYPE_RANGE_DESC);
+    }
+    return false;
+  }
+
+  /**
+    Check if the results from this operation will joined with results 
+    from the next operation using a join buffer (instead of plain nested loop).
+    @return True if using a join buffer. 
+  */
+  bool Table_access::uses_join_cache() const
+  {
+    return get_join_tab()->next_select == sub_select_cache;
+  }
+
+};
+// namespace AQP

=== added file 'sql/abstract_query_plan.h'
--- a/sql/abstract_query_plan.h	1970-01-01 00:00:00 +0000
+++ b/sql/abstract_query_plan.h	2012-01-05 14:41:08 +0000
@@ -0,0 +1,313 @@
+/*
+   Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
+
+   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 ABSTRACT_QUERY_PLAN_H_INCLUDED
+#define ABSTRACT_QUERY_PLAN_H_INCLUDED
+
+struct TABLE;
+struct st_join_table;
+typedef st_join_table JOIN_TAB;
+class JOIN;
+class Item;
+class Item_field;
+class Item_equal_iterator;
+
+#include "sql_list.h"
+
+/**
+  Abstract query plan (AQP) is an interface for examining certain aspects of 
+  query plans without accessing mysqld internal classes (JOIN_TAB, SQL_SELECT 
+  etc.) directly.
+
+  AQP maps join execution plans, as represented by mysqld internals, to a set 
+  of facade classes. Non-join operations such as sorting and aggregation is
+  currently *not* modelled in the AQP.
+
+  The AQP models an n-way join as a sequence of the n table access operations
+  that the MySQL server would execute as part of its nested loop join 
+  execution. (Each such table access operation is a scan of a table or index,
+  or an index lookup.) For each lookup operation, it is possible to examine 
+  the expression that represents each field in the key.
+
+  A storage enging will typically use the AQP for finding sections of a join
+  execution plan that may be executed in the engine rather than in mysqld. By 
+  using the AQP rather than the mysqld internals directly, the coupling between
+  the engine and mysqld is reduced.
+*/
+namespace AQP
+{
+  class Table_access;
+
+  /**
+    This class represents a query plan for an n-way join, in the form a 
+    sequence of n table access operations that will execute as a nested loop 
+    join.
+  */
+  class Join_plan : public Sql_alloc
+  {
+    friend class Equal_set_iterator;
+    friend class Table_access;
+  public:
+
+    explicit Join_plan(const JOIN* join);
+
+    ~Join_plan();
+
+    const Table_access* get_table_access(uint access_no) const;
+
+    uint get_access_count() const;
+
+    /**
+      Can filesort(), normally required by execution of GROUP BY 
+      or ORDER BY, be skipped due to the columns already being
+      accessible in required sorted order.
+    */
+    bool group_by_filesort_is_skippable() const;
+    bool order_by_filesort_is_skippable() const;
+
+  private:
+    /** 
+      Array of the JOIN_TABs that are the internal representation of table
+      access operations.
+    */
+    const JOIN_TAB* const m_join_tabs;
+
+    /** Number of table access operations. */
+    const uint m_access_count;
+    Table_access* m_table_accesses;
+
+    const JOIN_TAB* get_join_tab(uint join_tab_no) const;
+
+    // No copying.
+    Join_plan(const Join_plan&);
+    Join_plan& operator=(const Join_plan&);
+  }; 
+  // class Join_plan
+
+
+  /**
+    This class is an iterator for iterating over sets of fields (columns) that
+    should have the same value. For example, if the query is
+    SELECT * FROM T1, T2, T3 WHERE T1.b = T2.a AND T2.a = T3.a
+    then there would be such a set of {T1.b, T2.a, T3.a}.
+  */
+  class Equal_set_iterator : public Sql_alloc
+  {
+  public:
+    explicit Equal_set_iterator(Item_equal& item_equal)
+    : m_iterator(item_equal) {}
+
+    const Item_field* next()
+    { return m_iterator++; }
+
+  private:
+    /**
+      This class is implemented in terms of this mysqld internal class.
+     */
+    Item_equal_iterator m_iterator;
+
+    // No copying.
+    Equal_set_iterator(const Equal_set_iterator&);
+    Equal_set_iterator& operator=(const Equal_set_iterator&);
+  }; 
+  // class Equal_set_iterator
+
+  /** The type of a table access operation. */
+  enum enum_access_type
+  {
+    /** For default initialization.*/
+    AT_VOID,
+    /** Value has already been fetched / determined by optimizer.*/
+    AT_FIXED,
+    /** Do a lookup of a single primary key.*/
+    AT_PRIMARY_KEY,
+    /** Do a lookup of a single unique index key.*/
+    AT_UNIQUE_KEY,
+    /** Scan an ordered index with a single upper and lower bound pair.*/
+    AT_ORDERED_INDEX_SCAN,
+    /** Do a multi range read for a set of primary keys.*/
+    AT_MULTI_PRIMARY_KEY,
+    /** Do a multi range read for a set of unique index keys.*/
+    AT_MULTI_UNIQUE_KEY,
+    /** 
+      Do a multi range read for a mix of ranges (for which there is an
+      ordered index), and either primary keys or unique index keys.
+    */
+    AT_MULTI_MIXED,
+    /** Scan a table. (No index is assumed to be used.) */
+    AT_TABLE_SCAN,
+    /** Access method will not be chosen before the execution phase.*/
+    AT_UNDECIDED,
+    /**
+      The access method has properties that prevents it from being pushed to a 
+      storage engine.
+     */
+    AT_OTHER
+  };
+
+  /** The type of join operation require */
+  enum enum_join_type
+  {
+    JT_OUTER_JOIN,
+    JT_INNER_JOIN,
+    JT_SEMI_JOIN
+  };
+
+  /**
+    This class represents an access operation on a table, such as a table
+    scan, or a scan or lookup via an index. A Table_access object is always
+    owned by a Join_plan object, such that the life time of the Table_access 
+    object ends when the life time of the owning Join_plan object ends.
+   */
+  class Table_access : public Sql_alloc
+  {
+    friend class Join_plan;
+    friend inline bool equal(const Table_access*, const Table_access*);
+  public:
+
+    const Join_plan* get_join_plan() const;
+
+    enum_access_type get_access_type() const;
+
+    const char* get_other_access_reason() const;
+
+    enum_join_type get_join_type(const Table_access* parent) const;
+
+    uint get_no_of_key_fields() const;
+
+    const Item* get_key_field(uint field_no) const;
+
+    const KEY_PART_INFO* get_key_part_info(uint field_no) const;
+
+    uint get_access_no() const;
+
+    int get_index_no() const;
+
+    TABLE* get_table() const;
+
+    double get_fanout() const;
+
+    Item_equal* get_item_equal(const Item_field* field_item) const;
+
+    void dbug_print() const;
+
+    bool is_fixed_ordered_index() const;
+
+    bool uses_join_cache() const;
+
+  private:
+
+    /** Backref. to the Join_plan which this Table_access is part of */
+    const Join_plan* m_join_plan;
+
+    /** This operation corresponds to m_root_tab[m_tab_no].*/
+    uint m_tab_no;
+
+    /** The type of this operation.*/
+    mutable enum_access_type m_access_type;
+
+    /** 
+      The reason for getting m_access_type==AT_OTHER. Used for explain extended.
+    */
+    mutable const char* m_other_access_reason;
+
+    /** The index to use for this operation (if applicable )*/
+    mutable int m_index_no;
+
+    explicit Table_access();
+
+    const JOIN_TAB* get_join_tab() const;
+
+    void compute_type_and_index() const;
+
+    /** No copying*/
+    Table_access(const Table_access&);
+    Table_access& operator=(const Table_access&);
+  }; 
+  // class Table_access
+
+  /**
+    Get the n'th table access operation.
+    @param access_no The index of the table access operation to fetch.
+    @return The access_no'th table access operation.
+  */
+  inline const Table_access* Join_plan::get_table_access(uint access_no) const
+  {
+    DBUG_ASSERT(access_no < m_access_count);
+    return m_table_accesses + access_no;
+  }
+
+  /**
+     @return The number of table access operations in the nested loop join.
+  */
+  inline uint Join_plan::get_access_count() const
+  { 
+    return m_access_count;
+  }
+
+  /** Get the Join_plan that this Table_access belongs to.*/
+  inline const Join_plan* Table_access::get_join_plan() const
+  {
+    return m_join_plan;
+  }
+
+  /** Get the type of this operation.*/
+  inline enum_access_type Table_access::get_access_type() const
+  {
+    if (m_access_type == AT_VOID)
+      compute_type_and_index();
+    return m_access_type;
+  }
+
+  /** 
+    Get a description of the reason for getting access_type==AT_OTHER. To be 
+    used for informational messages.
+    @return A string that should be assumed to have the same life time as the
+    Table_access object.
+  */
+  inline const char* Table_access::get_other_access_reason() const
+  {
+    if (m_access_type == AT_VOID)
+      compute_type_and_index();
+    return m_other_access_reason;
+  }
+
+  /**
+    @return The number of the index to use for this access operation (
+    or -1 for non-index operations).
+  */
+  inline int Table_access::get_index_no() const
+  {
+    if (m_access_type == AT_VOID)
+      compute_type_and_index();
+	
+    return m_index_no;
+  }
+
+  /** 
+    Get the number of this Table_access within the enclosing Join_plan. 
+    (This number will be in the range 0 to Join_plan::get_access_count() - 1.)
+  */
+  inline uint Table_access::get_access_no() const
+  { 
+    return m_tab_no;
+  }
+
+}; 
+// namespace AQP
+
+#endif

=== modified file 'sql/handler.cc'
--- a/sql/handler.cc	2011-12-15 14:18:46 +0000
+++ b/sql/handler.cc	2012-01-05 14:41:08 +0000
@@ -4337,6 +4337,48 @@ int ha_table_exists_in_engine(THD* thd, 
   DBUG_RETURN(args.err);
 }
 
+/**
+  Prepare (sub-) sequences of joins in this statement 
+  which may be pushed to each storage engine for execution.
+*/
+struct st_make_pushed_join_args
+{
+  AQP::Join_plan* plan;  // Query plan provided by optimizer
+  uint pushed;           // #operations which was pushed.
+  int err;               // Error code to return.
+};
+
+static my_bool make_pushed_join_handlerton(THD *thd, plugin_ref plugin,
+                                   void *arg)
+{
+  st_make_pushed_join_args *vargs= (st_make_pushed_join_args *)arg;
+  handlerton *hton= plugin_data(plugin, handlerton *);
+
+  if (hton && hton->make_pushed_join)
+  {
+    uint pushed= 0;
+    const int error= hton->make_pushed_join(hton, thd, vargs->plan, &pushed);
+    if (unlikely(error))
+    {
+      vargs->err = error;
+      return TRUE;
+    }
+    vargs->pushed+= pushed;
+  }
+  return FALSE;
+}
+
+int ha_make_pushed_joins(THD *thd, AQP::Join_plan* plan, uint* pushed)
+{
+  DBUG_ENTER("ha_make_pushed_joins");
+  st_make_pushed_join_args args= {plan, 0, 0};
+  plugin_foreach(thd, make_pushed_join_handlerton,
+                 MYSQL_STORAGE_ENGINE_PLUGIN, &args);
+  *pushed = args.pushed;
+  DBUG_PRINT("exit", ("pushed cnt: %d, error: %d", args.pushed, args.err));
+  DBUG_RETURN(args.err);
+}
+
 #ifdef HAVE_NDB_BINLOG
 /*
   TODO: change this into a dynamic struct

=== modified file 'sql/handler.h'
--- a/sql/handler.h	2011-11-30 11:36:14 +0000
+++ b/sql/handler.h	2012-01-05 14:41:08 +0000
@@ -396,6 +396,30 @@ typedef ulonglong my_xid; // this line i
 #define COMPATIBLE_DATA_YES 0
 #define COMPATIBLE_DATA_NO  1
 
+namespace AQP {
+  class Join_plan;
+};
+
+/* Flag used for test_push_flag() */
+enum ha_push_flag {
+
+  /* Handler want to block const table optimization */
+  HA_PUSH_BLOCK_CONST_TABLE
+
+  /* Handler reports a pushed join as having multiple dependencies 
+     if its results does not only depend on the root operation:
+     ie. results from some child operations does not only depend
+     on results from the root operation and/or other child operations
+     within this pushed join 
+   */
+  ,HA_PUSH_MULTIPLE_DEPENDENCY
+
+  /* Handler is unable to return the result in sorted order using an
+     ordered index on the parent operation.
+   */
+  ,HA_PUSH_NO_ORDERED_INDEX
+};
+
 /**
   struct xid_t is binary compatible with the XID structure as
   in the X/Open CAE Specification, Distributed Transaction Processing:
@@ -802,6 +826,9 @@ struct handlerton
                      const char *wild, bool dir, List<LEX_STRING> *files);
    int (*table_exists_in_engine)(handlerton *hton, THD* thd, const char *db,
                                  const char *name);
+   int (*make_pushed_join)(handlerton *hton, THD* thd,
+                           AQP::Join_plan* plan,
+                           uint* pushed);
    uint32 license; /* Flag for Engine License */
    void *data; /* Location for engines to keep personal structures */
 };
@@ -2227,6 +2254,39 @@ public:
    in_range_check_pushed_down= false;
  }
 
+  /**
+    Reports #tables included in pushed join which this
+    handler instance is part of. ==0 -> Not pushed
+  */
+  virtual uint number_of_pushed_joins() const
+  { return 0; }
+
+  /**
+    If this handler instance is part of a pushed join sequence
+    returned TABLE instance being root of the pushed query?
+  */
+  virtual const TABLE* root_of_pushed_join() const
+  { return NULL; }
+
+  /**
+    If this handler instance is a child in a pushed join sequence
+    returned TABLE instance being my parent?
+  */
+  virtual const TABLE* parent_of_pushed_join() const
+  { return NULL; }
+
+  virtual bool test_push_flag(enum ha_push_flag flag) const
+  {
+    return FALSE;
+  }
+
+  virtual int index_read_pushed(uchar * buf, const uchar * key,
+                             key_part_map keypart_map)
+  { return  HA_ERR_WRONG_COMMAND; }
+
+  virtual int index_next_pushed(uchar * buf)
+  { return  HA_ERR_WRONG_COMMAND; }
+
  virtual bool check_if_incompatible_data(HA_CREATE_INFO *create_info,
 					 uint table_changes)
  { return COMPATIBLE_DATA_NO; }
@@ -2619,6 +2679,9 @@ int ha_rollback_to_savepoint(THD *thd, S
 int ha_savepoint(THD *thd, SAVEPOINT *sv);
 int ha_release_savepoint(THD *thd, SAVEPOINT *sv);
 
+/* Build pushed joins in handlers implementing this feature */
+int ha_make_pushed_joins(THD *thd, AQP::Join_plan* plan, uint* pushed);
+
 /* these are called by storage engines */
 void trans_register_ha(THD *thd, bool all, handlerton *ht);
 

=== modified file 'sql/opt_explain.cc'
--- a/sql/opt_explain.cc	2011-12-14 12:32:55 +0000
+++ b/sql/opt_explain.cc	2012-01-05 14:41:08 +0000
@@ -728,6 +728,40 @@ void Explain_table_base::explain_extra_c
        table->file->pushed_idx_cond) || (tab && tab->cache_idx_cond))
     str_extra->append(STRING_WITH_LEN("; Using index condition"));
 
+  const TABLE* pushed_root= table->file->root_of_pushed_join();
+  if (pushed_root)
+  {
+    char buf[64];
+    int len;
+    int pushed_id= 0;
+
+    for (JOIN_TAB* prev= join->join_tab; prev <= tab; prev++)
+    {
+      const TABLE* prev_root= prev->table->file->root_of_pushed_join();
+      if (prev_root == prev->table)
+      {
+        pushed_id++;
+        if (prev_root == pushed_root)
+          break;
+      }
+    }
+    if (pushed_root == table)
+    {
+      uint pushed_count= tab->table->file->number_of_pushed_joins();
+      len= my_snprintf(buf, sizeof(buf)-1,
+                       "; Parent of %d pushed join@%d",
+                       pushed_count, pushed_id);
+    }
+    else
+    {
+      len= my_snprintf(buf, sizeof(buf)-1,
+                       "; Child of '%s' in pushed join@%d",
+                       tab->table->file->parent_of_pushed_join()->alias,
+                       pushed_id);
+    }
+    str_extra->append(buf,len);
+  }
+
   switch (quick_type) {
   case QUICK_SELECT_I::QS_TYPE_ROR_UNION:
   case QUICK_SELECT_I::QS_TYPE_ROR_INTERSECT:

=== modified file 'sql/sql_executor.cc'
--- a/sql/sql_executor.cc	2012-01-05 13:13:15 +0000
+++ b/sql/sql_executor.cc	2012-01-05 14:41:08 +0000
@@ -81,6 +81,8 @@ static int join_ft_read_next(READ_RECORD
 static int join_read_always_key_or_null(JOIN_TAB *tab);
 static int join_read_next_same_or_null(READ_RECORD *info);
 static int join_read_record_no_init(JOIN_TAB *tab);
+static int join_read_linked_first(JOIN_TAB *tab);
+static int join_read_linked_next(READ_RECORD *info);
 // Create list for using with tempory table
 static bool change_to_use_tmp_fields(THD *thd, Ref_ptr_array ref_pointer_array,
 				     List<Item> &new_list1,
@@ -136,6 +138,41 @@ JOIN::exec()
 
   THD_STAGE_INFO(thd, stage_executing);
 
+  /**
+    Set up modified access function for pushed joins.
+  */
+  {
+    int active_pushed_joins= 0;
+
+    // Set up table accessors for child operations of pushed joins
+    for (uint i=const_tables ; i < tables ; i++)
+    {
+      JOIN_TAB *tab=join_tab+i;
+
+      uint pushed_joins= tab->table->file->number_of_pushed_joins();
+      if (pushed_joins > 0)
+      {
+        if (tab->table->file->root_of_pushed_join() == tab->table)
+        {
+          active_pushed_joins += pushed_joins;
+        }
+        else  
+        {
+          // Is child of a pushed join operation:
+          // Replace 'read_key' access with its linked counterpart 
+          // ... Which is effectively a NOOP as the row is read 
+          //    as part of the linked operation
+          tab->read_first_record= join_read_linked_first;
+          DBUG_ASSERT(tab->read_record.read_record != 
+                      join_read_next_same_or_null);
+          tab->read_record.read_record= join_read_linked_next;
+          tab->read_record.unlock_row= rr_unlock_row;
+        }
+        active_pushed_joins--;
+      }
+    }
+    DBUG_ASSERT(active_pushed_joins==0);
+  }
   if (prepare_result(&columns_list))
     DBUG_VOID_RETURN;
 
@@ -2828,6 +2865,77 @@ join_read_key_unlock_row(st_join_table *
     tab->ref.use_count--;
 }
 
+/**
+  Read a table *assumed* to be included in execution of a pushed join.
+  This is the counterpart of join_read_key() / join_read_always_key()
+  for child tables in a pushed join.
+
+    When the table access is performed as part of the pushed join,
+    all 'linked' child colums are prefetched together with the parent row.
+    The handler will then only format the row as required by MySQL and set
+    'table->status' accordingly.
+
+    However, there may be situations where the prepared pushed join was not
+    executed as assumed. It is the responsibility of the handler to handle
+    these situation by letting ::index_read_pushed() then effectively do a 
+    plain old' index_read_map(..., HA_READ_KEY_EXACT);
+  
+  @param tab			Table to read
+
+  @retval
+    0	Row was found
+  @retval
+    -1   Row was not found
+  @retval
+    1   Got an error (other than row not found) during read
+*/
+static int
+join_read_linked_first(JOIN_TAB *tab)
+{
+  TABLE *table= tab->table;
+  DBUG_ENTER("join_read_linked_first");
+
+  DBUG_ASSERT(!tab->sorted); // Pushed child can't be sorted
+  if (!table->file->inited)
+    table->file->ha_index_init(tab->ref.key, tab->sorted);
+
+  if (cp_buffer_from_ref(tab->join->thd, table, &tab->ref))
+  {
+    table->status=STATUS_NOT_FOUND;
+    DBUG_RETURN(-1);
+  }
+
+  // 'read' itself is a NOOP: 
+  //  handler::index_read_pushed() only unpack the prefetched row and set 'status'
+  int error=table->file->index_read_pushed(table->record[0],
+                                      tab->ref.key_buff,
+                                      make_prev_keypart_map(tab->ref.key_parts));
+  if (unlikely(error && error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE))
+    DBUG_RETURN(report_error(table, error));
+
+  table->null_row=0;
+  int rc= table->status ? -1 : 0;
+  DBUG_RETURN(rc);
+}
+
+
+static int
+join_read_linked_next(READ_RECORD *info)
+{
+  TABLE *table= info->table;
+  DBUG_ENTER("join_read_linked_next");
+
+  int error=table->file->index_next_pushed(table->record[0]);
+  if (error)
+  {
+    if (unlikely(error != HA_ERR_END_OF_FILE))
+      DBUG_RETURN(report_error(table, error));
+    table->status= STATUS_GARBAGE;
+    DBUG_RETURN(-1);
+  }
+  DBUG_RETURN(error);
+}
+
 /*
   ref access method implementation: "read_first" function
 
@@ -2909,8 +3017,19 @@ join_read_last_key(JOIN_TAB *tab)
 
 	/* ARGSUSED */
 static int
-join_no_more_records(READ_RECORD *info __attribute__((unused)))
+join_no_more_records(READ_RECORD *info)
 {
+  /**
+   * When a pushed join completes, and its results did not only depend on
+   * the key of this root operations: ('tab->ref.key_buff')
+   * Results from this pushed join can not be reused 
+   * for later queries having the same root key.
+   * (ref: join_read_key(), join_read_const() & join_read_system()
+   */
+  if (info->table->file->test_push_flag(HA_PUSH_MULTIPLE_DEPENDENCY))
+  {
+    info->table->status= STATUS_GARBAGE;
+  }
   return -1;
 }
 

=== modified file 'sql/sql_optimizer.cc'
--- a/sql/sql_optimizer.cc	2012-01-05 13:13:15 +0000
+++ b/sql/sql_optimizer.cc	2012-01-05 14:41:08 +0000
@@ -36,6 +36,7 @@
 #include "sql_parse.h"
 #include "my_bit.h"
 #include "lock.h"
+#include "abstract_query_plan.h"
 
 #include <algorithm>
 using std::max;
@@ -102,6 +103,7 @@ static bool
 only_eq_ref_tables(JOIN *join, ORDER *order, table_map tables,
                    table_map *cached_eq_ref_tables, table_map
                    *eq_ref_tables);
+static int  make_pushed_join(THD *thd, JOIN *join);
 
 
 
@@ -894,6 +896,9 @@ JOIN::optimize()
     }
   }
 
+  if (make_pushed_join(thd, this))
+    DBUG_RETURN(1);
+
   tmp_having= having;
   if (!(select_options & SELECT_DESCRIBE))
   {
@@ -924,6 +929,48 @@ setup_subq_exit:
 }
 
 
+static int
+make_pushed_join(THD *thd, JOIN *join)
+{
+  // Let handler extract whatever it might implement of pushed joins
+  AQP::Join_plan plan(join);
+  uint pushed;
+
+  const int error= ha_make_pushed_joins(thd, &plan, &pushed);
+  if (unlikely(error))
+    return error;
+  if (pushed==0)
+    return 0;          // Didn't push anything
+
+  /* If we just pushed a join containing an ORDER BY and/or a GROUP BY clause,
+   * we have to ensure that we can skip the sort by scanning an ordered index.
+   * Else we have to signal now that we have to write to a temporary table
+   * which will later be filesorted.
+   *
+   * Furthermore, the handler implementing the pushed join may have
+   * restrictions which prevents it from returning a sorted resultset.
+   */
+  if (join->const_tables < join->tables &&
+      join->join_tab[join->const_tables].table->file->number_of_pushed_joins() > 0)
+  {
+    const handler *ha=join->join_tab[join->const_tables].table->file;
+
+    if (join->group_list && join->simple_group &&
+        (!plan.group_by_filesort_is_skippable() || ha->test_push_flag(HA_PUSH_NO_ORDERED_INDEX)))
+    {
+      join->need_tmp= 1;
+      join->simple_group= 0;
+    }
+    else if (join->order && join->simple_order &&
+             (!plan.order_by_filesort_is_skippable() || ha->test_push_flag(HA_PUSH_NO_ORDERED_INDEX)))
+    {
+      join->need_tmp= 1;
+      join->simple_order= 0;
+    }
+  }
+  return 0;
+}
+
 /**
   Set NESTED_JOIN::counter=0 in all nested joins in passed list.
 
@@ -2941,6 +2988,14 @@ make_join_statistics(JOIN *join, TABLE_L
       */
       extract_method= extract_no_table;
     }
+    else if (table->file->test_push_flag(HA_PUSH_BLOCK_CONST_TABLE))
+    {
+      /*
+        Handler implements pushed joins, and prefer const tables to
+        be pushed together with rest of the pushed query.
+      */
+      extract_method= extract_no_table;
+    }
     else if (*s->on_expr_ref)
     {
       /* s is the only inner table of an outer join, extract empty tables */
@@ -3103,11 +3158,13 @@ const_table_extraction_done:
              1. are full-text searched, or
              2. are part of nested outer join, or
              3. are part of semi-join
+             4. are blocked by handler for const table optimize.
           */
 	  if (eq_part.is_prefix(table->key_info[key].key_parts) &&
-              !table->fulltext_searched &&                           // 1
-              !tl->in_outer_join_nest() &&                           // 2
-              !(tl->embedding && tl->embedding->sj_on_expr))         // 3
+              !table->fulltext_searched &&                             // 1
+              !tl->in_outer_join_nest() &&                             // 2
+              !(tl->embedding && tl->embedding->sj_on_expr) &&         // 3
+              !table->file->test_push_flag(HA_PUSH_BLOCK_CONST_TABLE)) // 4
 	  {
             if (table->key_info[key].flags & HA_NOSAME)
             {

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bzr push into mysql-trunk branch (ole.john.aske:3705 to 3706) WL#5940Ole John Aske9 Jan