Adding upstream version 1:10.5.12.upstream/1%10.5.12upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1671 insertions, 0 deletions

diff --git a/sql/sql_derived.cc b/sql/sql_derived.cc
new file mode 100644
index 00000000..f8ee3475
--- /dev/null
+++ b/sql/sql_derived.cc
@@ -0,0 +1,1671 @@
+/*
+   Copyright (c) 2002, 2011, Oracle and/or its affiliates.
+   Copyright (c) 2010, 2021, MariaDB
+
+   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 02110-1335  USA */
+
+
+/*
+  Derived tables
+  These were introduced by Sinisa <sinisa@mysql.com>
+*/
+
+
+#include "mariadb.h"                         /* NO_EMBEDDED_ACCESS_CHECKS */
+#include "sql_priv.h"
+#include "unireg.h"
+#include "sql_select.h"
+#include "derived_handler.h"
+#include "sql_base.h"
+#include "sql_view.h"                         // check_duplicate_names
+#include "sql_acl.h"                          // SELECT_ACL
+#include "sql_class.h"
+#include "sql_derived.h"
+#include "sql_cte.h"
+#include "my_json_writer.h"
+#include "opt_trace.h"
+
+typedef bool (*dt_processor)(THD *thd, LEX *lex, TABLE_LIST *derived);
+
+static bool mysql_derived_init(THD *thd, LEX *lex, TABLE_LIST *derived);
+static bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived);
+static bool mysql_derived_optimize(THD *thd, LEX *lex, TABLE_LIST *derived);
+static bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived);
+static bool mysql_derived_create(THD *thd, LEX *lex, TABLE_LIST *derived);
+static bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived);
+static bool mysql_derived_reinit(THD *thd, LEX *lex, TABLE_LIST *derived);
+static bool mysql_derived_merge_for_insert(THD *thd, LEX *lex,
+                                           TABLE_LIST *derived);
+
+dt_processor processors[]=
+{
+  &mysql_derived_init,
+  &mysql_derived_prepare,
+  &mysql_derived_optimize,
+  &mysql_derived_merge,
+  &mysql_derived_merge_for_insert,
+  &mysql_derived_create,
+  &mysql_derived_fill,
+  &mysql_derived_reinit,
+};
+
+/*
+  Run specified phases on all derived tables/views in given LEX.
+
+  @param lex              LEX for this thread
+  @param phases           phases to run derived tables/views through
+
+  @return FALSE  OK
+  @return TRUE   Error
+*/
+bool
+mysql_handle_derived(LEX *lex, uint phases)
+{
+  bool res= FALSE;
+  DBUG_ENTER("mysql_handle_derived");
+  DBUG_PRINT("enter", ("phases: 0x%x", phases));
+  if (!lex->derived_tables)
+    DBUG_RETURN(FALSE);
+
+  lex->thd->derived_tables_processing= TRUE;
+
+  for (uint phase= 0; phase < DT_PHASES && !res; phase++)
+  {
+    uint phase_flag= DT_INIT << phase;
+    if (phase_flag > phases)
+      break;
+    if (!(phases & phase_flag))
+      continue;
+
+    for (SELECT_LEX *sl= lex->all_selects_list;
+	 sl && !res;
+	 sl= sl->next_select_in_list())
+    {
+      TABLE_LIST *cursor= sl->get_table_list();
+      sl->changed_elements|= TOUCHED_SEL_DERIVED;
+      /*
+        DT_MERGE_FOR_INSERT is not needed for views/derived tables inside
+        subqueries. Views and derived tables of subqueries should be
+        processed normally.
+      */
+      if (phases == DT_MERGE_FOR_INSERT &&
+          cursor && (cursor->top_table()->select_lex !=
+                     lex->first_select_lex()))
+        continue;
+      for (;
+	   cursor && !res;
+	   cursor= cursor->next_local)
+      {
+        if (!cursor->is_view_or_derived() && phases == DT_MERGE_FOR_INSERT)
+          continue;
+        uint8 allowed_phases= (cursor->is_merged_derived() ? DT_PHASES_MERGE :
+                               DT_PHASES_MATERIALIZE | DT_MERGE_FOR_INSERT);
+        /*
+          Skip derived tables to which the phase isn't applicable.
+          TODO: mark derived at the parse time, later set it's type
+          (merged or materialized)
+        */
+        if ((phase_flag != DT_PREPARE && !(allowed_phases & phase_flag)) ||
+            (cursor->merged_for_insert && phase_flag != DT_REINIT &&
+             phase_flag != DT_PREPARE))
+          continue;
+	res= (*processors[phase])(lex->thd, lex, cursor);
+      }
+      if (lex->describe)
+      {
+	/*
+	  Force join->join_tmp creation, because we will use this JOIN
+	  twice for EXPLAIN and we have to have unchanged join for EXPLAINing
+	*/
+	sl->uncacheable|= UNCACHEABLE_EXPLAIN;
+	sl->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN;
+      }
+    }
+  }
+  lex->thd->derived_tables_processing= FALSE;
+  DBUG_RETURN(res);
+}
+
+/*
+  Run through phases for the given derived table/view.
+
+  @param lex             LEX for this thread
+  @param derived         the derived table to handle
+  @param phase_map       phases to process tables/views through
+
+  @details
+
+  This function process the derived table (view) 'derived' to performs all
+  actions that are to be done on the table at the phases specified by
+  phase_map. The processing is carried out starting from the actions
+  performed at the earlier phases (those having smaller ordinal numbers).
+
+  @note
+  This function runs specified phases of the derived tables handling on the
+  given derived table/view. This function is used in the chain of calls:
+    SELECT_LEX::handle_derived ->
+      TABLE_LIST::handle_derived ->
+        mysql_handle_single_derived
+  This chain of calls implements the bottom-up handling of the derived tables:
+  i.e. most inner derived tables/views are handled first. This order is
+  required for the all phases except the merge and the create steps.
+  For the sake of code simplicity this order is kept for all phases.
+
+  @return FALSE ok
+  @return TRUE  error
+*/
+
+bool
+mysql_handle_single_derived(LEX *lex, TABLE_LIST *derived, uint phases)
+{
+  bool res= FALSE;
+  uint8 allowed_phases= (derived->is_merged_derived() ? DT_PHASES_MERGE :
+                         DT_PHASES_MATERIALIZE);
+  DBUG_ENTER("mysql_handle_single_derived");
+  DBUG_PRINT("enter", ("phases: 0x%x  allowed: 0x%x  alias: '%s'",
+                       phases, allowed_phases,
+                       (derived->alias.str ? derived->alias.str : "<NULL>")));
+  if (!lex->derived_tables)
+    DBUG_RETURN(FALSE);
+
+  if (derived->select_lex)
+    derived->select_lex->changed_elements|= TOUCHED_SEL_DERIVED;
+  else
+    DBUG_ASSERT(derived->prelocking_placeholder);
+  lex->thd->derived_tables_processing= TRUE;
+
+  for (uint phase= 0; phase < DT_PHASES; phase++)
+  {
+    uint phase_flag= DT_INIT << phase;
+    if (phase_flag > phases)
+      break;
+    if (!(phases & phase_flag))
+      continue;
+    /* Skip derived tables to which the phase isn't applicable.  */
+    if (phase_flag != DT_PREPARE &&
+        !(allowed_phases & phase_flag))
+      continue;
+
+    if ((res= (*processors[phase])(lex->thd, lex, derived)))
+      break;
+  }
+
+  lex->thd->derived_tables_processing= FALSE;
+  DBUG_RETURN(res);
+}
+
+
+/**
+  Merge a derived table/view into the embedding select
+
+  @param thd     thread handle
+  @param lex     LEX of the embedding query.
+  @param derived reference to the derived table.
+
+  @details
+  This function merges the given derived table / view into the parent select
+  construction. Any derived table/reference to view occurred in the FROM
+  clause of the embedding select is represented by a TABLE_LIST structure a
+  pointer to which is passed to the function as in the parameter 'derived'.
+  This structure contains  the number/map, alias, a link to SELECT_LEX of the
+  derived table and other info. If the 'derived' table is used in a nested join
+  then additionally the structure contains a reference to the ON expression
+  for this join.
+
+  The merge process results in elimination of the derived table (or the
+  reference to a view) such that:
+    - the FROM list of the derived table/view is wrapped into a nested join
+      after which the nest is added to the FROM list of the embedding select
+    - the WHERE condition of the derived table (view) is ANDed with the ON
+      condition attached to the table.
+
+  @note
+  Tables are merged into the leaf_tables list, original derived table is removed
+  from this list also. SELECT_LEX::table_list list is left untouched.
+  Where expression is merged with derived table's on_expr and can be found after
+  the merge through the SELECT_LEX::table_list.
+
+  Examples of the derived table/view merge:
+
+  Schema:
+  Tables: t1(f1), t2(f2), t3(f3)
+  View v1: SELECT f1 FROM t1 WHERE f1 < 1
+
+  Example with a view:
+    Before merge:
+
+    The query (Q1): SELECT f1,f2 FROM t2 LEFT JOIN v1 ON f1 = f2
+
+       (LEX of the main query)
+                 |
+           (select_lex)
+                 |
+         (FROM table list)
+                 |
+            (join list)= t2, v1
+                             / \
+                            /  (on_expr)= (f1 = f2)
+                            |
+                    (LEX of the v1 view)
+                            |
+                       (select_lex)= SELECT f1 FROM t1 WHERE f1 < 1
+
+
+    After merge:
+
+    The rewritten query Q1 (Q1'):
+      SELECT f1,f2 FROM t2 LEFT JOIN (t1) ON ((f1 = f2) and (f1 < 1))
+
+        (LEX of the main query)
+                   |
+             (select_lex)
+                   |
+           (FROM table list)
+                   |
+               (join list)= t2, (t1)
+                                    \
+                                   (on_expr)= (f1 = f2) and (f1 < 1)
+
+    In this example table numbers are assigned as follows:
+      (outer select): t2 - 1, v1 - 2
+      (inner select): t1 - 1
+    After the merge table numbers will be:
+      (outer select): t2 - 1, t1 - 2
+
+  Example with a derived table:
+    The query Q2:
+      SELECT f1,f2
+       FROM (SELECT f1 FROM t1, t3 WHERE f1=f3 and f1 < 1) tt, t2
+       WHERE f1 = f2
+
+    Before merge:
+              (LEX of the main query)
+                        |
+                  (select_lex)
+                  /           \
+       (FROM table list)   (WHERE clause)= (f1 = f2)
+                  |
+           (join list)= tt, t2
+                       / \
+                      /  (on_expr)= (empty)
+                     /
+           (select_lex)= SELECT f1 FROM t1, t3 WHERE f1 = f3 and f1 < 1
+
+    After merge:
+
+    The rewritten query Q2 (Q2'):
+      SELECT f1,f2
+       FROM (t1, t3) JOIN t2 ON (f1 = f3 and f1 < 1)
+       WHERE f1 = f2
+
+              (LEX of the main query)
+                        |
+                  (select_lex)
+                  /           \
+       (FROM table list)   (WHERE clause)= (f1 = f2)
+                 |
+          (join list)= t2, (t1, t3)
+                                   \
+                                 (on_expr)= (f1 = f3 and f1 < 1)
+
+  In this example table numbers are assigned as follows:
+    (outer select): tt - 1, t2 - 2
+    (inner select): t1 - 1, t3 - 2
+  After the merge table numbers will be:
+    (outer select): t1 - 1, t2 - 2, t3 - 3
+
+  @return FALSE if derived table/view were successfully merged.
+  @return TRUE if an error occur.
+*/
+
+static
+bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  bool res= FALSE;
+  SELECT_LEX *dt_select= derived->get_single_select();
+  table_map map;
+  uint tablenr;
+  SELECT_LEX *parent_lex= derived->select_lex;
+  Query_arena *arena, backup;
+  DBUG_ENTER("mysql_derived_merge");
+  DBUG_PRINT("enter", ("Alias: '%s'  Unit: %p",
+                       (derived->alias.str ? derived->alias.str : "<NULL>"),
+                       derived->get_unit()));
+  const char *cause= NULL;
+
+  if (derived->merged)
+  {
+
+    DBUG_PRINT("info", ("Irreversibly merged: exit"));
+    DBUG_RETURN(FALSE);
+  }
+
+  if (dt_select->uncacheable & UNCACHEABLE_RAND)
+  {
+    /* There is random function => fall back to materialization. */
+    cause= "Random function in the select";
+    if (unlikely(thd->trace_started()))
+    {
+      OPT_TRACE_VIEWS_TRANSFORM(thd, trace_wrapper, trace_derived,
+                          derived->is_derived() ? "derived" : "view",
+                          derived->alias.str ? derived->alias.str : "<NULL>",
+                          derived->get_unit()->first_select()->select_number,
+                          "materialized");
+      trace_derived.add("cause", cause);
+    }
+    derived->change_refs_to_fields();
+    derived->set_materialized_derived();
+    DBUG_RETURN(FALSE);
+  }
+
+  if (derived->dt_handler)
+  {
+    derived->change_refs_to_fields();
+    derived->set_materialized_derived();
+    DBUG_RETURN(FALSE);
+  }
+
+  arena= thd->activate_stmt_arena_if_needed(&backup);  // For easier test
+
+  if (!derived->merged_for_insert || 
+      (derived->is_multitable() && 
+       (thd->lex->sql_command == SQLCOM_UPDATE_MULTI ||
+        thd->lex->sql_command == SQLCOM_DELETE_MULTI)))
+  {
+    /*
+      Check whether there is enough free bits in table map to merge subquery.
+      If not - materialize it. This check isn't cached so when there is a big
+      and small subqueries, and the bigger one can't be merged it wouldn't
+      block the smaller one.
+    */
+    if (parent_lex->get_free_table_map(&map, &tablenr) ||
+       dt_select->leaf_tables.elements + tablenr > MAX_TABLES)
+    {
+      /* There is no enough table bits, fall back to materialization. */
+      cause= "Not enough table bits to merge subquery";
+      goto unconditional_materialization;
+    }
+
+    if (dt_select->options & OPTION_SCHEMA_TABLE)
+      parent_lex->options |= OPTION_SCHEMA_TABLE;
+
+    if (!derived->get_unit()->prepared)
+    {
+      dt_select->leaf_tables.empty();
+      make_leaves_list(thd, dt_select->leaf_tables, derived, TRUE, 0);
+    } 
+
+    derived->nested_join= (NESTED_JOIN*) thd->calloc(sizeof(NESTED_JOIN));
+    if (!derived->nested_join)
+    {
+      res= TRUE;
+      goto exit_merge;
+    }
+
+    /* Merge derived table's subquery in the parent select. */
+    if (parent_lex->merge_subquery(thd, derived, dt_select, tablenr, map))
+    {
+      res= TRUE;
+      goto exit_merge;
+    }
+
+    /*
+      exclude select lex so it doesn't show up in explain.
+      do this only for derived table as for views this is already done.
+
+      From sql_view.cc
+        Add subqueries units to SELECT into which we merging current view.
+        unit(->next)* chain starts with subqueries that are used by this
+        view and continues with subqueries that are used by other views.
+        We must not add any subquery twice (otherwise we'll form a loop),
+        to do this we remember in end_unit the first subquery that has
+        been already added.
+    */
+    derived->get_unit()->exclude_level();
+    if (parent_lex->join) 
+      parent_lex->join->table_count+= dt_select->join->table_count - 1;
+  }
+  derived->merged= TRUE;
+  if (derived->get_unit()->prepared)
+  {
+    Item *expr= derived->on_expr;
+    expr= and_conds(thd, expr, dt_select->join ? dt_select->join->conds : 0);
+    if (expr)
+      expr->top_level_item();
+
+    if (expr && (derived->prep_on_expr || expr != derived->on_expr))
+    {
+      derived->on_expr= expr;
+      derived->prep_on_expr= expr->copy_andor_structure(thd);
+    }
+    thd->where= "on clause";
+    if (derived->on_expr &&
+        derived->on_expr->fix_fields_if_needed_for_bool(thd, &derived->on_expr))
+    {
+      res= TRUE; /* purecov: inspected */
+      goto exit_merge;
+    }
+    // Update used tables cache according to new table map
+    if (derived->on_expr)
+    {
+      derived->on_expr->fix_after_pullout(parent_lex, &derived->on_expr,
+                                          TRUE);
+      fix_list_after_tbl_changes(parent_lex, &derived->nested_join->join_list);
+    }
+  }
+
+exit_merge:
+  if (arena)
+    thd->restore_active_arena(arena, &backup);
+  DBUG_RETURN(res);
+
+unconditional_materialization:
+
+  if (unlikely(thd->trace_started()))
+  {
+    OPT_TRACE_VIEWS_TRANSFORM(thd,trace_wrapper, trace_derived,
+                        derived->is_derived() ? "derived" : "view",
+                        derived->alias.str ? derived->alias.str : "<NULL>",
+                        derived->get_unit()->first_select()->select_number,
+                        "materialized");
+    trace_derived.add("cause", cause);
+  }
+
+  derived->change_refs_to_fields();
+  derived->set_materialized_derived();
+  if (!derived->table || !derived->table->is_created())
+    res= mysql_derived_create(thd, lex, derived);
+  goto exit_merge;
+}
+
+
+/**
+  Merge a view for the embedding INSERT/UPDATE/DELETE
+
+  @param thd     thread handle
+  @param lex     LEX of the embedding query.
+  @param derived reference to the derived table.
+
+  @details
+  This function substitutes the derived table for the first table from
+  the query of the derived table thus making it a correct target table for the
+  INSERT/UPDATE/DELETE statements. As this operation is correct only for
+  single table views only, for multi table views this function does nothing.
+  The derived parameter isn't checked to be a view as derived tables aren't
+  allowed for INSERT/UPDATE/DELETE statements.
+
+  @return FALSE if derived table/view were successfully merged.
+  @return TRUE if an error occur.
+*/
+
+static
+bool mysql_derived_merge_for_insert(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  DBUG_ENTER("mysql_derived_merge_for_insert");
+  DBUG_PRINT("enter", ("Alias: '%s'  Unit: %p",
+                       (derived->alias.str ? derived->alias.str : "<NULL>"),
+                       derived->get_unit()));
+  DBUG_PRINT("info", ("merged_for_insert: %d  is_materialized_derived: %d  "
+                      "is_multitable: %d  single_table_updatable: %d  "
+                      "merge_underlying_list: %d",
+                      derived->merged_for_insert,
+                      derived->is_materialized_derived(),
+                      derived->is_multitable(),
+                      derived->single_table_updatable(),
+                      derived->merge_underlying_list != 0));
+  if (derived->merged_for_insert)
+    DBUG_RETURN(FALSE);
+  if (derived->init_derived(thd, FALSE))
+    DBUG_RETURN(TRUE);
+  if (derived->is_materialized_derived())
+    DBUG_RETURN(mysql_derived_prepare(thd, lex, derived));
+  if ((thd->lex->sql_command == SQLCOM_UPDATE_MULTI ||
+       thd->lex->sql_command == SQLCOM_DELETE_MULTI))
+    DBUG_RETURN(FALSE);
+  if (!derived->is_multitable())
+  {
+    if (!derived->single_table_updatable())
+      DBUG_RETURN(derived->create_field_translation(thd));
+    if (derived->merge_underlying_list)
+    {
+      derived->table= derived->merge_underlying_list->table;
+      derived->schema_table= derived->merge_underlying_list->schema_table;
+      derived->merged_for_insert= TRUE;
+      DBUG_ASSERT(derived->table);
+    }
+  }
+  DBUG_RETURN(FALSE);
+}
+
+
+/*
+  Initialize a derived table/view
+
+  @param thd	     Thread handle
+  @param lex         LEX of the embedding query.
+  @param derived     reference to the derived table.
+
+  @detail
+  Fill info about derived table/view without preparing an
+  underlying select. Such as: create a field translation for views, mark it as
+  a multitable if it is and so on.
+
+  @return
+    false  OK
+    true   Error
+*/
+
+static
+bool mysql_derived_init(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  SELECT_LEX_UNIT *unit= derived->get_unit();
+  DBUG_ENTER("mysql_derived_init");
+  DBUG_PRINT("enter", ("Alias: '%s'  Unit: %p",
+                       (derived->alias.str ? derived->alias.str : "<NULL>"),
+                       derived->get_unit()));
+
+  // Skip already prepared views/DT
+  if (!unit || unit->prepared)
+    DBUG_RETURN(FALSE);
+
+  bool res= derived->init_derived(thd, TRUE);
+
+  derived->updatable= derived->updatable && derived->is_view();
+
+  DBUG_RETURN(res);
+}
+
+
+/**
+  @brief
+    Prevent name resolution out of context of ON expressions in derived tables
+
+  @param
+    join_list  list of tables used in from list of a derived
+
+  @details
+    The function sets the Name_resolution_context::outer_context to NULL
+    for all ON expressions contexts in the given join list. It does this
+    recursively for all nested joins the list contains.
+*/
+
+static void nullify_outer_context_for_on_clauses(List<TABLE_LIST>& join_list)
+{
+  List_iterator<TABLE_LIST> li(join_list);
+  while (TABLE_LIST *table= li++)
+  {
+    if (table->on_context)
+      table->on_context->outer_context= NULL;
+    if (table->nested_join)
+      nullify_outer_context_for_on_clauses(table->nested_join->join_list);
+  }
+}
+
+
+/*
+  Create temporary table structure (but do not fill it)
+
+  @param thd	     Thread handle
+  @param lex         LEX of the embedding query.
+  @param derived     reference to the derived table.
+
+  @detail
+  Prepare underlying select for a derived table/view. To properly resolve
+  names in the embedding query the TABLE structure is created. Actual table
+  is created later by the mysql_derived_create function.
+
+  This function is called before any command containing derived table
+  is executed. All types of derived tables are handled by this function:
+  - Anonymous derived tables, or
+  - Named derived tables (aka views).
+
+  The table reference, contained in @c derived, is updated with the
+  fields of a new temporary table.
+  Derived tables are stored in @c thd->derived_tables and closed by
+  close_thread_tables().
+
+  This function is part of the procedure that starts in
+  open_and_lock_tables(), a procedure that - among other things - introduces
+  new table and table reference objects (to represent derived tables) that
+  don't exist in the privilege database. This means that normal privilege
+  checking cannot handle them. Hence this function does some extra tricks in
+  order to bypass normal privilege checking, by exploiting the fact that the
+  current state of privilege verification is attached as GRANT_INFO structures
+  on the relevant TABLE and TABLE_REF objects.
+
+  For table references, the current state of accrued access is stored inside
+  TABLE_LIST::grant. Hence this function must update the state of fulfilled
+  privileges for the new TABLE_LIST, an operation which is normally performed
+  exclusively by the table and database access checking functions,
+  check_access() and check_grant(), respectively. This modification is done
+  for both views and anonymous derived tables: The @c SELECT privilege is set
+  as fulfilled by the user. However, if a view is referenced and the table
+  reference is queried against directly (see TABLE_LIST::referencing_view),
+  the state of privilege checking (GRANT_INFO struct) is copied as-is to the
+  temporary table.
+
+  Only the TABLE structure is created here, actual table is created by the
+  mysql_derived_create function.
+
+  @note This function sets @c SELECT_ACL for @c TEMPTABLE views as well as
+  anonymous derived tables, but this is ok since later access checking will
+  distinguish between them.
+
+  @see mysql_handle_derived(), mysql_derived_fill(), GRANT_INFO
+
+  @return
+    false  OK
+    true   Error
+*/
+
+static
+bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  SELECT_LEX_UNIT *unit= derived->get_unit();
+  bool res= FALSE;
+  DBUG_ENTER("mysql_derived_prepare");
+  DBUG_PRINT("enter", ("unit: %p  table_list: %p  alias: '%s'",
+                       unit, derived, derived->alias.str));
+  if (!unit)
+    DBUG_RETURN(FALSE);
+
+  SELECT_LEX *first_select= unit->first_select();
+
+  if (derived->is_recursive_with_table() &&
+      !derived->is_with_table_recursive_reference() &&
+      !derived->with->rec_result && derived->with->get_sq_rec_ref())
+  {
+    /*
+      This is a non-recursive reference to a recursive CTE whose
+      specification unit has not been prepared at the regular processing of
+      derived table references. This can happen  only in the case when
+      the specification unit has no recursive references at the top level. 
+      Force the preparation of the specification unit. Use a recursive
+      table reference from a subquery for this.
+    */
+    DBUG_ASSERT(derived->with->get_sq_rec_ref());
+    if (unlikely(mysql_derived_prepare(lex->thd, lex,
+                                       derived->with->get_sq_rec_ref())))
+      DBUG_RETURN(TRUE);
+  }
+
+  if (unit->prepared && derived->is_recursive_with_table() &&
+      !derived->table)
+  {
+    /* 
+      Here 'derived' is either a non-recursive table reference to a recursive
+      with table or a recursive table reference to a recursvive table whose
+      specification has been already prepared (a secondary recursive table
+      reference.
+    */ 
+    if (!(derived->derived_result= new (thd->mem_root) select_unit(thd)))
+      DBUG_RETURN(TRUE); // out of memory
+    thd->create_tmp_table_for_derived= TRUE;
+    res= derived->derived_result->create_result_table(
+                                  thd, &unit->types, FALSE,
+                                  (first_select->options |
+                                   thd->variables.option_bits |
+                                   TMP_TABLE_ALL_COLUMNS),
+                                  &derived->alias, FALSE, FALSE, FALSE, 0);
+    thd->create_tmp_table_for_derived= FALSE;
+
+    if (likely(!res) && !derived->table)
+    {
+      derived->derived_result->set_unit(unit);
+      derived->table= derived->derived_result->table;
+      if (derived->is_with_table_recursive_reference())
+      {
+        /* Here 'derived" is a secondary recursive table reference */
+         unit->with_element->rec_result->rec_table_refs.push_back(derived);
+      }
+    }
+    DBUG_ASSERT(derived->table || res);
+    goto exit;
+  }
+
+  // Skip already prepared views/DT
+  if (unit->prepared ||
+      (derived->merged_for_insert && 
+       !(derived->is_multitable() &&
+         (thd->lex->sql_command == SQLCOM_UPDATE_MULTI ||
+          thd->lex->sql_command == SQLCOM_DELETE_MULTI))))
+  {
+    /*
+       System versioned tables may still require to get versioning conditions
+       when modifying view (see vers_setup_conds()). Only UPDATE and DELETE are
+       affected because they use WHERE condition.
+    */
+    if (!unit->prepared &&
+        derived->table->versioned() &&
+        derived->merge_underlying_list &&
+        /* choose only those merged views that do not select from other views */
+        !derived->merge_underlying_list->merge_underlying_list)
+    {
+      switch (thd->lex->sql_command)
+      {
+      case SQLCOM_DELETE:
+      case SQLCOM_DELETE_MULTI:
+      case SQLCOM_UPDATE:
+      case SQLCOM_UPDATE_MULTI:
+        if ((res= first_select->vers_setup_conds(thd,
+                                                 derived->merge_underlying_list)))
+          goto exit;
+        if (derived->merge_underlying_list->where)
+        {
+          Query_arena_stmt on_stmt_arena(thd);
+          derived->where= and_items(thd, derived->where,
+                                    derived->merge_underlying_list->where);
+        }
+      default:
+        break;
+      }
+    }
+    DBUG_RETURN(FALSE);
+  }
+
+  /* prevent name resolving out of derived table */
+  for (SELECT_LEX *sl= first_select; sl; sl= sl->next_select())
+  {
+    // Prevent it for the WHERE clause
+    sl->context.outer_context= 0;
+
+    // And for ON clauses, if there are any
+    nullify_outer_context_for_on_clauses(*sl->join_list);
+
+    if (!derived->is_with_table_recursive_reference() ||
+        (!derived->with->with_anchor && 
+         !derived->with->is_with_prepared_anchor()))
+    {
+      /* 
+        Prepare underlying views/DT first unless 'derived' is a recursive
+        table reference and either the anchors from the specification of
+        'derived' has been already prepared or there no anchor in this
+        specification
+      */  
+      if ((res= sl->handle_derived(lex, DT_PREPARE)))
+        goto exit;
+    }
+    if (derived->outer_join && sl->first_cond_optimization)
+    {
+      /* Mark that table is part of OUTER JOIN and fields may be NULL */
+      for (TABLE_LIST *cursor= (TABLE_LIST*) sl->table_list.first;
+           cursor;
+           cursor= cursor->next_local)
+        cursor->outer_join|= JOIN_TYPE_OUTER;
+    }
+  }
+
+  if (unlikely(thd->trace_started()))
+  {
+    /*
+      Add to optimizer trace whether a derived table/view
+      is merged into the parent select or not.
+    */
+    OPT_TRACE_VIEWS_TRANSFORM(thd, trace_wrapper, trace_derived,
+                    derived->is_derived() ? "derived" : "view",
+                    derived->alias.str ? derived->alias.str : "<NULL>",
+                    derived->get_unit()->first_select()->select_number,
+                    derived->is_merged_derived() ? "merged" : "materialized");
+  }
+  /*
+    Above cascade call of prepare is important for PS protocol, but after it
+    is called we can check if we really need prepare for this derived
+  */
+  if (derived->merged)
+  {
+    DBUG_PRINT("info", ("Irreversibly merged: exit"));
+    DBUG_RETURN(FALSE);
+  }
+
+  derived->fill_me= FALSE;
+
+  if ((!derived->is_with_table_recursive_reference() ||
+       !derived->derived_result) &&
+      !(derived->derived_result= new (thd->mem_root) select_unit(thd)))
+    DBUG_RETURN(TRUE); // out of memory
+
+  // st_select_lex_unit::prepare correctly work for single select
+  if ((res= unit->prepare(derived, derived->derived_result, 0)))
+    goto exit;
+  if (derived->with &&
+      (res= derived->with->process_columns_of_derived_unit(thd, unit)))
+    goto exit;
+  if ((res= check_duplicate_names(thd, unit->types, 0)))
+    goto exit;
+
+  /*
+    Check whether we can merge this derived table into main select.
+    Depending on the result field translation will or will not
+    be created.
+  */
+  if (!derived->is_with_table_recursive_reference() &&
+      derived->init_derived(thd, FALSE))
+    goto exit;
+
+  /*
+    Temp table is created so that it hounours if UNION without ALL is to be 
+    processed
+
+    As 'distinct' parameter we always pass FALSE (0), because underlying
+    query will control distinct condition by itself. Correct test of
+    distinct underlying query will be is_unit_op &&
+    !unit->union_distinct->next_select() (i.e. it is union and last distinct
+    SELECT is last SELECT of UNION).
+  */
+  thd->create_tmp_table_for_derived= TRUE;
+  if (!(derived->table) &&
+      derived->derived_result->create_result_table(thd, &unit->types, FALSE,
+                                                   (first_select->options |
+                                                   thd->variables.option_bits |
+                                                   TMP_TABLE_ALL_COLUMNS),
+                                                   &derived->alias,
+                                                   FALSE, FALSE, FALSE,
+                                                   0))
+  { 
+    thd->create_tmp_table_for_derived= FALSE;
+    goto exit;
+  }
+  thd->create_tmp_table_for_derived= FALSE;
+
+  if (!derived->table)
+    derived->table= derived->derived_result->table;
+  DBUG_ASSERT(derived->table);
+  if (derived->is_derived() && derived->is_merged_derived())
+    first_select->mark_as_belong_to_derived(derived);
+
+  derived->dt_handler= derived->find_derived_handler(thd);
+  if (derived->dt_handler)
+  {
+    char query_buff[4096];
+    String derived_query(query_buff, sizeof(query_buff), thd->charset());
+    derived_query.length(0);
+    derived->derived->print(&derived_query,
+                            enum_query_type(QT_VIEW_INTERNAL | 
+                                            QT_ITEM_ORIGINAL_FUNC_NULLIF |
+                                            QT_PARSABLE));
+    if (!thd->make_lex_string(&derived->derived_spec,
+                              derived_query.ptr(), derived_query.length()))
+    {
+      delete derived->dt_handler;
+      derived->dt_handler= NULL;
+    }
+  }
+
+exit:
+  /* Hide "Unknown column" or "Unknown function" error */
+  if (derived->view)
+  {
+    if (thd->is_error() &&
+        (thd->get_stmt_da()->sql_errno() == ER_BAD_FIELD_ERROR ||
+        thd->get_stmt_da()->sql_errno() == ER_FUNC_INEXISTENT_NAME_COLLISION ||
+        thd->get_stmt_da()->sql_errno() == ER_SP_DOES_NOT_EXIST))
+    {
+      thd->clear_error();
+      my_error(ER_VIEW_INVALID, MYF(0), derived->db.str,
+               derived->table_name.str);
+    }
+  }
+
+  /*
+    if it is preparation PS only or commands that need only VIEW structure
+    then we do not need real data and we can skip execution (and parameters
+    is not defined, too)
+  */
+  if (res)
+  {
+    if (!derived->is_with_table_recursive_reference())
+    {
+      if (derived->table && derived->table->s->tmp_table)
+        free_tmp_table(thd, derived->table);
+      delete derived->derived_result;
+    }
+  }
+  else
+  {
+    TABLE *table= derived->table;
+    table->derived_select_number= first_select->select_number;
+    table->s->tmp_table= INTERNAL_TMP_TABLE;
+#ifndef NO_EMBEDDED_ACCESS_CHECKS
+    if (derived->is_view())
+      table->grant= derived->grant;
+    else
+    {
+      DBUG_ASSERT(derived->is_derived());
+      DBUG_ASSERT(derived->is_anonymous_derived_table());
+      table->grant.privilege= SELECT_ACL;
+      derived->grant.privilege= SELECT_ACL;
+    }
+#endif
+    /* Add new temporary table to list of open derived tables */
+    if (!derived->is_with_table_recursive_reference())
+    {
+      table->next= thd->derived_tables;
+      thd->derived_tables= table;
+    }
+
+    /* If table is used by a left join, mark that any column may be null */
+    if (derived->outer_join)
+      table->maybe_null= 1;
+  }
+  DBUG_RETURN(res);
+}
+
+
+/**
+  Runs optimize phase for a derived table/view.
+
+  @param thd     thread handle
+  @param lex     LEX of the embedding query.
+  @param derived reference to the derived table.
+
+  @details
+  Runs optimize phase for given 'derived' derived table/view.
+  If optimizer finds out that it's of the type "SELECT a_constant" then this
+  functions also materializes it.
+
+  @return FALSE ok.
+  @return TRUE if an error occur.
+*/
+
+static
+bool mysql_derived_optimize(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  SELECT_LEX_UNIT *unit= derived->get_unit();
+  SELECT_LEX *first_select= unit->first_select();
+  SELECT_LEX *save_current_select= lex->current_select;
+  bool res= FALSE;
+  DBUG_ENTER("mysql_derived_optimize");
+  DBUG_PRINT("enter", ("Alias: '%s'  Unit: %p",
+                       (derived->alias.str ? derived->alias.str : "<NULL>"),
+                       derived->get_unit()));
+  if (derived->merged)
+  {
+    DBUG_PRINT("info", ("Irreversibly merged: exit"));
+    DBUG_RETURN(FALSE);
+  }
+
+  if (derived->is_materialized_derived() && derived->dt_handler)
+  {
+    /* Create an object for execution of the query specifying the table */
+    if (!(derived->pushdown_derived=
+            new (thd->mem_root) Pushdown_derived(derived, derived->dt_handler)))
+    {
+      delete derived->dt_handler;
+      derived->dt_handler= NULL;
+      DBUG_RETURN(TRUE);
+    }
+  }
+
+  lex->current_select= first_select;
+
+  if (unit->is_unit_op())
+  {
+    if (unit->optimized)
+      DBUG_RETURN(FALSE);
+    // optimize union without execution
+    res= unit->optimize();
+  }
+  else if (unit->derived)
+  {
+    if (!derived->is_merged_derived())
+    {
+      JOIN *join= first_select->join;
+      unit->set_limit(unit->global_parameters());
+      if (join &&
+          join->optimization_state == JOIN::OPTIMIZATION_PHASE_1_DONE &&
+          join->with_two_phase_optimization)
+      {
+        if (unit->optimized_2)
+          DBUG_RETURN(FALSE);
+        unit->optimized_2= TRUE;
+      }
+      else
+      {
+        if (unit->optimized)
+          DBUG_RETURN(FALSE);        
+	unit->optimized= TRUE;
+        if (!join)
+	{
+          /*
+            This happens when derived is used in SELECT for which
+            zer_result_cause != 0.
+            In this case join is already destroyed.
+	  */
+          DBUG_RETURN(FALSE);
+        }
+      }
+      if ((res= join->optimize()))
+        goto err;
+      if (join->table_count == join->const_tables)
+        derived->fill_me= TRUE;
+    }
+  }
+  /*
+    Materialize derived tables/views of the "SELECT a_constant" type.
+    Such tables should be materialized at the optimization phase for
+    correct constant evaluation.
+  */
+  if (!res && derived->fill_me && !derived->merged_for_insert)
+  {
+    if (derived->is_merged_derived())
+    {
+      derived->change_refs_to_fields();
+      derived->set_materialized_derived();
+    }
+    if ((res= mysql_derived_create(thd, lex, derived)))
+      goto err;
+    if ((res= mysql_derived_fill(thd, lex, derived)))
+      goto err;
+  }
+err:
+  lex->current_select= save_current_select;
+  DBUG_RETURN(res);
+}
+
+
+/**
+  Actually create result table for a materialized derived table/view.
+
+  @param thd     thread handle
+  @param lex     LEX of the embedding query.
+  @param derived reference to the derived table.
+
+  @details
+  This function actually creates the result table for given 'derived'
+  table/view, but it doesn't fill it.
+  'thd' and 'lex' parameters are not used  by this function.
+
+  @return FALSE ok.
+  @return TRUE if an error occur.
+*/
+
+static
+bool mysql_derived_create(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  DBUG_ENTER("mysql_derived_create");
+  DBUG_PRINT("enter", ("Alias: '%s'  Unit: %p",
+                       (derived->alias.str ? derived->alias.str : "<NULL>"),
+                       derived->get_unit()));
+  TABLE *table= derived->table;
+  SELECT_LEX_UNIT *unit= derived->get_unit();
+
+  if (table->is_created())
+    DBUG_RETURN(FALSE);
+  select_unit *result= derived->derived_result;
+  if (table->s->db_type() == TMP_ENGINE_HTON)
+  {
+    result->tmp_table_param.keyinfo= table->s->key_info;
+    if (create_internal_tmp_table(table, result->tmp_table_param.keyinfo,
+                                  result->tmp_table_param.start_recinfo,
+                                  &result->tmp_table_param.recinfo,
+                                  (unit->first_select()->options |
+                                   thd->variables.option_bits | TMP_TABLE_ALL_COLUMNS)))
+      DBUG_RETURN(TRUE);
+  }
+  if (open_tmp_table(table))
+    DBUG_RETURN(TRUE);
+  table->file->extra(HA_EXTRA_WRITE_CACHE);
+  table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
+  DBUG_RETURN(FALSE);
+}
+
+
+void TABLE_LIST::register_as_derived_with_rec_ref(With_element *rec_elem)
+{
+  rec_elem->derived_with_rec_ref.link_in_list(this, &this->next_with_rec_ref);
+  is_derived_with_recursive_reference= true;
+  get_unit()->uncacheable|= UNCACHEABLE_DEPENDENT;
+}
+
+
+bool TABLE_LIST::is_nonrecursive_derived_with_rec_ref()
+{
+  return is_derived_with_recursive_reference;
+}
+
+
+/**
+  @brief
+    Fill the recursive with table 
+
+  @param thd  The thread handle
+
+  @details
+    The method is called only for recursive with tables. 
+    The method executes the recursive part of the specification
+    of this with table until no more rows are added to the table
+    or the number of the performed iteration reaches the allowed
+    maximum. 
+
+  @retval
+    false   on success
+    true    on failure 
+*/
+
+bool TABLE_LIST::fill_recursive(THD *thd)
+{
+  bool rc= false;
+  st_select_lex_unit *unit= get_unit();
+  rc= with->instantiate_tmp_tables();
+  while (!rc && !with->all_are_stabilized())
+  {
+    if (with->level > thd->variables.max_recursive_iterations)
+      break;
+    with->prepare_for_next_iteration();
+    rc= unit->exec_recursive();
+  }
+  if (!rc)
+  {
+    TABLE *src= with->rec_result->table;
+    rc =src->insert_all_rows_into_tmp_table(thd,
+                                            table,
+                                            &with->rec_result->tmp_table_param,
+                                            true);
+  } 
+  return rc;
+}
+
+
+/*
+  Execute subquery of a materialized derived table/view and fill the result
+  table.
+
+  @param thd      Thread handle
+  @param lex      LEX for this thread
+  @param derived  reference to the derived table.
+
+  @details
+  Execute subquery of given 'derived' table/view and fill the result
+  table. After result table is filled, if this is not the EXPLAIN statement
+  and the table is not specified with a recursion the entire unit / node
+  is deleted. unit is deleted if UNION is used  for derived table and node
+  is deleted is it is a simple SELECT.
+  'lex' is unused and 'thd' is passed as an argument to an underlying function.
+
+  @note
+  If you use this function, make sure it's not called at prepare.
+  Due to evaluation of LIMIT clause it can not be used at prepared stage.
+
+  @return FALSE  OK
+  @return TRUE   Error
+*/
+
+static
+bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  Field_iterator_table field_iterator;
+  SELECT_LEX_UNIT *unit= derived->get_unit();
+  bool derived_is_recursive= derived->is_recursive_with_table();
+  bool res= FALSE;
+  DBUG_ENTER("mysql_derived_fill");
+  DBUG_PRINT("enter", ("Alias: '%s'  Unit: %p",
+                       (derived->alias.str ? derived->alias.str : "<NULL>"),
+                       derived->get_unit()));
+
+  if (unit->executed && !unit->uncacheable && !unit->describe &&
+      !derived_is_recursive)
+    DBUG_RETURN(FALSE);
+  /*check that table creation passed without problems. */
+  DBUG_ASSERT(derived->table && derived->table->is_created());
+  select_unit *derived_result= derived->derived_result;
+  SELECT_LEX *save_current_select= lex->current_select;
+
+  if (derived->pushdown_derived)
+  {
+    int res;
+    if (unit->executed)
+      DBUG_RETURN(FALSE);
+    /* Execute the query that specifies the derived table by a foreign engine */
+    res= derived->pushdown_derived->execute();
+    unit->executed= true;
+    delete derived->pushdown_derived;
+      DBUG_RETURN(res);
+  }
+
+  if (unit->executed && !derived_is_recursive &&
+      (unit->uncacheable & UNCACHEABLE_DEPENDENT))
+  {
+    if ((res= derived->table->file->ha_delete_all_rows()))
+      goto err;
+    JOIN *join= unit->first_select()->join;
+    join->first_record= false;
+    for (uint i= join->top_join_tab_count;
+         i < join->top_join_tab_count + join->aggr_tables;
+         i++)
+    { 
+      if ((res= join->join_tab[i].table->file->ha_delete_all_rows()))
+        goto err;
+    }   
+  }
+  
+  if (derived_is_recursive)
+  {
+    if (derived->is_with_table_recursive_reference())
+    {
+      /* Here only one iteration step is performed */
+      res= unit->exec_recursive();
+    }
+    else
+    {
+      /* In this case all iteration are performed */
+      res= derived->fill_recursive(thd);
+    }
+  }
+  else if (unit->is_unit_op())
+  {
+    // execute union without clean up
+    res= unit->exec();
+  }
+  else
+  {
+    SELECT_LEX *first_select= unit->first_select();
+    unit->set_limit(unit->global_parameters());
+    if (unit->lim.is_unlimited())
+      first_select->options&= ~OPTION_FOUND_ROWS;
+
+    lex->current_select= first_select;
+    res= mysql_select(thd,
+                      first_select->table_list.first,
+                      first_select->item_list, first_select->where,
+                      (first_select->order_list.elements+
+                       first_select->group_list.elements),
+                      first_select->order_list.first,
+                      first_select->group_list.first,
+                      first_select->having, (ORDER*) NULL,
+                      (first_select->options |thd->variables.option_bits |
+                       SELECT_NO_UNLOCK),
+                      derived_result, unit, first_select);
+  }
+
+  if (!res && !derived_is_recursive)
+  {
+    if (derived_result->flush())
+      res= TRUE;
+    unit->executed= TRUE;
+
+    if (derived->field_translation)
+    {
+      /* reset translation table to materialized table */
+      field_iterator.set_table(derived->table);
+      for (uint i= 0;
+           !field_iterator.end_of_fields();
+           field_iterator.next(), i= i + 1)
+      {
+        Item *item;
+
+        if (!(item= field_iterator.create_item(thd)))
+        {
+          res= TRUE;
+          break;
+        }
+        thd->change_item_tree(&derived->field_translation[i].item, item);
+      }
+    }
+  }
+err:
+  if (res || (!derived_is_recursive && !lex->describe && !unit->uncacheable))
+    unit->cleanup();
+  lex->current_select= save_current_select;
+
+  DBUG_RETURN(res);
+}
+
+
+/**
+  Re-initialize given derived table/view for the next execution.
+
+  @param  thd         thread handle
+  @param  lex         LEX for this thread
+  @param  derived     reference to the derived table.
+
+  @details
+  Re-initialize given 'derived' table/view for the next execution.
+  All underlying views/derived tables are recursively reinitialized prior
+  to re-initialization of given derived table.
+  'thd' and 'lex' are passed as arguments to called functions.
+
+  @return FALSE  OK
+  @return TRUE   Error
+*/
+
+static
+bool mysql_derived_reinit(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  DBUG_ENTER("mysql_derived_reinit");
+  DBUG_PRINT("enter", ("Alias: '%s'  Unit: %p",
+                       (derived->alias.str ? derived->alias.str : "<NULL>"),
+                       derived->get_unit()));
+  st_select_lex_unit *unit= derived->get_unit();
+
+  derived->merged_for_insert= FALSE;
+  unit->unclean();
+  unit->types.empty();
+  /* for derived tables & PS (which can't be reset by Item_subselect) */
+  unit->reinit_exec_mechanism();
+  unit->set_thd(thd);
+  DBUG_RETURN(FALSE);
+}
+
+
+/*
+  @brief
+    Given condition cond and transformer+argument, try transforming as many
+    conjuncts as possible.
+
+  @detail
+    The motivation of this function is to convert the condition that's being
+    pushed into a WHERE clause with derived_field_transformer_for_where or
+    with derived_grouping_field_transformer_for_where.
+    The transformer may fail for some sub-condition, in this case we want to
+    convert the most restrictive part of the condition that can be pushed.
+
+    This function only does it for top-level AND: conjuncts that could not be
+    converted are dropped.
+
+  @return
+    Converted condition, or NULL if nothing could be converted
+*/
+
+Item *transform_condition_or_part(THD *thd,
+                                  Item *cond,
+                                  Item_transformer transformer,
+                                  uchar *arg)
+{
+  if (cond->type() != Item::COND_ITEM ||
+      ((Item_cond*) cond)->functype() != Item_func::COND_AND_FUNC)
+  {
+    Item *new_item= cond->transform(thd, transformer, arg);
+      // Indicate that the condition is not pushable
+    if (!new_item)
+      cond->clear_extraction_flag();
+    return new_item;
+  }
+
+  List_iterator<Item> li(*((Item_cond*) cond)->argument_list());
+  Item *item;
+  while ((item=li++))
+  {
+    Item *new_item= item->transform(thd, transformer, arg);
+    if (!new_item)
+    {
+      // Indicate that the condition is not pushable
+      item->clear_extraction_flag();
+      li.remove();
+    }
+    else
+      li.replace(new_item);
+  }
+
+  switch (((Item_cond*) cond)->argument_list()->elements)
+  {
+  case 0:
+    return NULL;
+  case 1:
+    return ((Item_cond*) cond)->argument_list()->head();
+  default:
+    return cond;
+  }
+}
+
+
+/**
+  @brief
+    Extract condition that can be pushed into a derived table/view
+   
+  @param thd       the thread handle
+  @param cond      current condition
+  @param derived   the reference to the derived table/view
+
+  @details
+    This function builds the most restrictive condition depending only on
+    the derived table/view (directly or indirectly through equality) that
+    can be extracted from the given condition cond and pushes it into the
+    derived table/view.
+
+    Example of the transformation:
+
+    SELECT *
+    FROM t1,
+    (
+      SELECT x,MAX(y) AS max_y
+      FROM t2
+      GROUP BY x
+    ) AS d_tab
+    WHERE d_tab.x>1 AND d_tab.max_y<30;
+
+    =>
+
+    SELECT *
+    FROM t1,
+    (
+      SELECT x,z,MAX(y) AS max_y
+      FROM t2
+      WHERE x>1
+      HAVING max_y<30
+      GROUP BY x
+    ) AS d_tab
+    WHERE d_tab.x>1 AND d_tab.max_y<30;
+
+    In details:
+    1. Check what pushable formula can be extracted from cond
+    2. Build a clone PC of the formula that can be extracted
+       (the clone is built only if the extracted formula is a AND subformula
+        of cond or conjunction of such subformulas)
+    Do for every select specifying derived table/view:
+    3. If there is no HAVING clause prepare PC to be conjuncted with
+       WHERE clause of the select. Otherwise do 4-7.
+    4. Check what formula PC_where can be extracted from PC to be pushed
+       into the WHERE clause of the select
+    5. Build PC_where and if PC_where is a conjunct(s) of PC remove it from PC
+       getting PC_having
+    6. Prepare PC_where to be conjuncted with the WHERE clause of the select
+    7. Prepare PC_having to be conjuncted with the HAVING clause of the select
+  @note
+    This method is similar to pushdown_cond_for_in_subquery()
+
+  @retval TRUE   if an error occurs
+  @retval FALSE  otherwise
+*/
+
+bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived)
+{
+  DBUG_ENTER("pushdown_cond_for_derived");
+  if (!cond)
+    DBUG_RETURN(false);
+
+  st_select_lex_unit *unit= derived->get_unit();
+  st_select_lex *first_sl= unit->first_select();
+  st_select_lex *sl= first_sl;
+
+  if (derived->prohibit_cond_pushdown)
+    DBUG_RETURN(false);
+
+  /* Do not push conditions into constant derived */
+  if (unit->executed)
+    DBUG_RETURN(false);
+
+  /* Do not push conditions into recursive with tables */
+  if (derived->is_recursive_with_table())
+    DBUG_RETURN(false);
+
+  /* Do not push conditions into unit with global ORDER BY ... LIMIT */
+  if (unit->fake_select_lex && unit->fake_select_lex->explicit_limit)
+    DBUG_RETURN(false);
+
+  /* Check whether any select of 'unit' allows condition pushdown */
+  bool some_select_allows_cond_pushdown= false;
+  for (; sl; sl= sl->next_select())
+  {
+    if (sl->cond_pushdown_is_allowed())
+    {
+      some_select_allows_cond_pushdown= true;
+      break;
+    }
+  }
+  if (!some_select_allows_cond_pushdown)
+    DBUG_RETURN(false);
+
+  /* 1. Check what pushable formula can be extracted from cond */
+  Item *extracted_cond;
+  cond->check_pushable_cond(&Item::pushable_cond_checker_for_derived,
+                            (uchar *)(&derived->table->map));
+  /* 2. Build a clone PC of the formula that can be extracted */
+  extracted_cond=
+    cond->build_pushable_cond(thd,
+                              &Item::pushable_equality_checker_for_derived,
+                              ((uchar *)&derived->table->map));
+  if (!extracted_cond)
+  {
+    /* Nothing can be pushed into the derived table */
+    DBUG_RETURN(false);
+  }
+
+  st_select_lex *save_curr_select= thd->lex->current_select;
+  for (; sl; sl= sl->next_select())
+  {
+    Item *extracted_cond_copy;
+    if (!sl->cond_pushdown_is_allowed())
+      continue;
+    /*
+      For each select of the unit except the last one
+      create a clone of extracted_cond
+    */
+    extracted_cond_copy= !sl->next_select() ?
+                         extracted_cond :
+                         extracted_cond->build_clone(thd);
+    if (!extracted_cond_copy)
+      continue;
+
+    /*
+      Rename the columns of all non-first selects of a union to be compatible
+      by names with the columns of the first select. It will allow to use copies
+      of the same expression pushed into having clauses of different selects.
+    */
+    if (sl != first_sl)
+    {
+      DBUG_ASSERT(sl->item_list.elements == first_sl->item_list.elements);
+      List_iterator_fast<Item> it(sl->item_list);
+      List_iterator_fast<Item> nm_it(unit->types);
+      while (Item *item= it++)
+        item->share_name_with(nm_it++);
+    }
+
+    /* Collect fields that are used in the GROUP BY of sl */
+    if (sl->have_window_funcs())
+    {
+      if (sl->group_list.first || sl->join->implicit_grouping)
+        continue;
+      ORDER *common_partition_fields=
+         sl->find_common_window_func_partition_fields(thd);
+      if (!common_partition_fields)
+        continue;
+      sl->collect_grouping_fields_for_derived(thd, common_partition_fields);
+    }
+    else
+      sl->collect_grouping_fields_for_derived(thd, sl->group_list.first);
+
+    Item *remaining_cond= NULL;
+    /* Do 4-6 */
+    sl->pushdown_cond_into_where_clause(thd, extracted_cond_copy,
+                                    &remaining_cond,
+                                    &Item::derived_field_transformer_for_where,
+                                    (uchar *) sl);
+
+    if (!remaining_cond)
+      continue;
+    /*
+       7. Prepare PC_having to be conjuncted with the HAVING clause of
+          the select
+    */
+    remaining_cond=
+      remaining_cond->transform(thd,
+                                &Item::derived_field_transformer_for_having,
+                                (uchar *) sl);
+    if (!remaining_cond)
+      continue;
+
+    if (remaining_cond->walk(&Item::cleanup_excluding_const_fields_processor,
+                             0, 0))
+      continue;
+
+    mark_or_conds_to_avoid_pushdown(remaining_cond);
+
+    sl->cond_pushed_into_having= remaining_cond;
+  }
+  thd->lex->current_select= save_curr_select;
+  DBUG_RETURN(false);
+}
+
+
+/**
+  @brief
+    Look for provision of the derived_handler interface by a foreign engine
+
+  @param thd   The thread handler
+
+  @details
+    The function looks through its tables of the query that specifies this
+    derived table searching for a table whose handlerton owns a
+    create_derived call-back function. If the call of this function returns
+    a derived_handler interface object then the server will push the query
+    specifying the derived table into this engine.
+    This is a responsibility of the create_derived call-back function to
+    check whether the engine can execute the query.
+
+  @retval the found derived_handler if the search is successful
+          0  otherwise
+*/
+
+derived_handler *TABLE_LIST::find_derived_handler(THD *thd)
+{
+  if (!derived || is_recursive_with_table())
+    return 0;
+  for (SELECT_LEX *sl= derived->first_select(); sl; sl= sl->next_select())
+  {
+    if (!(sl->join))
+      continue;
+    for (TABLE_LIST *tbl= sl->join->tables_list; tbl; tbl= tbl->next_local)
+    {
+      if (!tbl->table)
+	continue;
+      handlerton *ht= tbl->table->file->partition_ht();
+      if (!ht->create_derived)
+        continue;
+      derived_handler *dh= ht->create_derived(thd, this);
+      if (dh)
+      {
+        dh->set_derived(this);
+        return dh;
+      }
+    }
+  }
+  return 0;
+}
+
+
+TABLE_LIST *TABLE_LIST::get_first_table()
+{
+  for (SELECT_LEX *sl= derived->first_select(); sl; sl= sl->next_select())
+  {
+    if (!(sl->join))
+      continue;
+    for (TABLE_LIST *tbl= sl->join->tables_list; tbl; tbl= tbl->next_local)
+    {
+      if (!tbl->table)
+	continue;
+      return tbl;
+    }
+  }
+  return 0;
+}