MWL#106: Backport optimizations for derived tables and views.

The main consolidated patch.

1 files changed, 803 insertions, 181 deletions

diff --git a/sql/sql_derived.cc b/sql/sql_derived.cc
index 22240d3a300..ff56f5291bc 100644
--- a/sql/sql_derived.cc
+++ b/sql/sql_derived.cc
@@ -23,38 +23,79 @@
 #include "mysql_priv.h"
 #include "sql_select.h"
 
+typedef bool (*dt_processor)(THD *thd, LEX *lex, TABLE_LIST *derived);
 
+bool mysql_derived_init(THD *thd, LEX *lex, TABLE_LIST *derived);
+bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived);
+bool mysql_derived_optimize(THD *thd, LEX *lex, TABLE_LIST *derived);
+bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived);
+bool mysql_derived_create(THD *thd, LEX *lex, TABLE_LIST *derived);
+bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived);
+bool mysql_derived_reinit(THD *thd, LEX *lex, TABLE_LIST *derived);
+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,
+};
 
 /*
-  Call given derived table processor (preparing or filling tables)
+  @brief
+  Run specified phases on all derived tables/views in given LEX.
 
-  SYNOPSIS
-    mysql_handle_derived()
-    lex                 LEX for this thread
-    processor           procedure of derived table processing
+  @param lex              LEX for this thread
+  @param phases           phases to run derived tables/views through
 
-  RETURN
-    FALSE  OK
-    TRUE   Error
+  @return FALSE  OK
+  @return TRUE   Error
 */
-
 bool
-mysql_handle_derived(LEX *lex, bool (*processor)(THD*, LEX*, TABLE_LIST*))
+mysql_handle_derived(LEX *lex, uint phases)
 {
   bool res= FALSE;
-  if (lex->derived_tables)
+  THD *thd= lex->thd;
+  if (!lex->derived_tables)
+    return FALSE;
+
+  lex->thd->derived_tables_processing= TRUE;
+
+  for (uint phase= 0; phase < DT_PHASES && !res; phase++)
   {
-    lex->thd->derived_tables_processing= TRUE;
+    uint phase_flag= DT_INIT << phase;
+    if (phase_flag > phases)
+      break;
+    if (!(phases & phase_flag))
+      continue;
+    if (phase_flag >= DT_CREATE && !thd->fill_derived_tables())
+      break;
+
     for (SELECT_LEX *sl= lex->all_selects_list;
-	 sl;
+	 sl && !res;
 	 sl= sl->next_select_in_list())
     {
       for (TABLE_LIST *cursor= sl->get_table_list();
-	   cursor;
+	   cursor && !res;
 	   cursor= cursor->next_local)
       {
-	if ((res= (*processor)(lex->thd, lex, cursor)))
-	  goto out;
+        uint8 allowed_phases= (cursor->is_merged_derived() ? DT_PHASES_MERGE :
+                               DT_PHASES_MATERIALIZE);
+        /*
+          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))
+          continue;
+	res= (*processors[phase])(lex->thd, lex, cursor);
       }
       if (lex->describe)
       {
@@ -67,30 +108,454 @@ mysql_handle_derived(LEX *lex, bool (*processor)(THD*, LEX*, TABLE_LIST*))
       }
     }
   }
-out:
+  lex->thd->derived_tables_processing= FALSE;
+  return res;
+}
+
+/*
+  @brief
+  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;
+  THD *thd= lex->thd;
+  uint8 allowed_phases= (derived->is_merged_derived() ? DT_PHASES_MERGE :
+                         DT_PHASES_MATERIALIZE);
+  if (!lex->derived_tables)
+    return FALSE;
+
+  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 (phase_flag >= DT_CREATE && !thd->fill_derived_tables())
+      break;
+
+    if ((res= (*processors[phase])(lex->thd, lex, derived)))
+      break;
+  }
   lex->thd->derived_tables_processing= FALSE;
   return res;
 }
 
 
 /**
-  @brief Create temporary table structure (but do not fill it).
+  @brief
+  Run specified phases for derived tables/views in the given list
 
-  @param thd Thread handle
-  @param lex LEX for this thread
-  @param orig_table_list TABLE_LIST for the upper SELECT
+  @param lex        LEX for this thread
+  @param table_list list of derived tables/view to handle
+  @param phase_map  phases to process tables/views through
 
-  @details 
+  @details
+  This function runs phases specified by the 'phases_map' on derived
+  tables/views found in the 'dt_list' with help of the
+  TABLE_LIST::handle_derived function.
+  'lex' is passed as an argument to the TABLE_LIST::handle_derived.
 
-  This function is called before any command containing derived tables is
-  executed. Currently the function is used for derived tables, i.e.
+  @return FALSE ok
+  @return TRUE  error
+*/
 
-  - Anonymous derived tables, or 
-  - Named derived tables (aka views) with the @c TEMPTABLE algorithm.
-   
-  The table reference, contained in @c orig_table_list, is updated with the
-  fields of a new temporary table.
+bool
+mysql_handle_list_of_derived(LEX *lex, TABLE_LIST *table_list, uint phases)
+{
+  for (TABLE_LIST *tl= table_list; tl; tl= tl->next_local)
+  {
+    if (tl->is_view_or_derived() &&
+        tl->handle_derived(lex, phases))
+      return TRUE;
+  }
+  return FALSE;
+}
+
+
+/**
+  @brief
+  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.
+*/
+
+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;
+
+  if (derived->merged)
+    return FALSE;
+
+  arena= thd->activate_stmt_arena_if_needed(&backup);  // For easier test
+  derived->merged= TRUE;
+  /*
+    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))
+  {
+    /* There is no enough table bits, fall back to materialization. */
+    derived->change_refs_to_fields();
+    derived->set_materialized_derived();
+    goto exit_merge;
+  }
+
+  if (dt_select->leaf_tables.elements + tablenr > MAX_TABLES)
+  {
+    /* There is no enough table bits, fall back to materialization. */
+    derived->change_refs_to_fields();
+    derived->set_materialized_derived();
+    goto exit_merge;
+  }
+
+  if (dt_select->options & OPTION_SCHEMA_TABLE)
+    parent_lex->options |= OPTION_SCHEMA_TABLE;
+
+  parent_lex->cond_count+= dt_select->cond_count;
+
+  if (!derived->get_unit()->prepared)
+  {
+    dt_select->leaf_tables.empty();
+    make_leaves_list(dt_select->leaf_tables, derived, TRUE, 0);
+  } 
+
+  if (!derived->merged_for_insert)
+  {  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(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->tables+= dt_select->join->tables - 1;
+  }
+  if (derived->get_unit()->prepared)
+  {
+    Item *expr= derived->on_expr;
+    expr= and_conds(expr, dt_select->join ? dt_select->join->conds : 0);
+    if (expr && (derived->prep_on_expr || expr != derived->on_expr))
+    {
+      derived->on_expr= expr;
+      derived->prep_on_expr= expr->copy_andor_structure(thd);
+    }
+    if (derived->on_expr &&
+        ((!derived->on_expr->fixed &&
+          derived->on_expr->fix_fields(thd, &derived->on_expr)) ||
+          derived->on_expr->check_cols(1)))
+    {
+      res= TRUE; /* purecov: inspected */
+      goto exit_merge;
+    }
+    // Update used tables cache according to new table map
+    if (derived->on_expr)
+      derived->on_expr->update_used_tables();
+  }
+
+exit_merge:
+  if (arena)
+    thd->restore_active_arena(arena, &backup);
+  return res;
+}
+
+
+/**
+  @brief
+  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.
+*/
+
+bool mysql_derived_merge_for_insert(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  SELECT_LEX *dt_select= derived->get_single_select();
+
+  if (derived->merged_for_insert)
+    return FALSE;
+  if (!derived->is_multitable())
+  {
+    TABLE_LIST *tl=((TABLE_LIST*)dt_select->table_list.first);
+    TABLE *table= tl->table;
+    /* preserve old map & tablenr. */
+    if (!derived->merged_for_insert && derived->table)
+      table->set_table_map(derived->table->map, derived->table->tablenr);
+
+    derived->table= table;
+    derived->schema_table=
+      ((TABLE_LIST*)dt_select->table_list.first)->schema_table;
+    if (!derived->merged)
+    {
+      Query_arena *arena, backup;
+      arena= thd->activate_stmt_arena_if_needed(&backup);  // For easier test
+      derived->select_lex->leaf_tables.push_back(tl);
+      derived->nested_join= (NESTED_JOIN*) thd->calloc(sizeof(NESTED_JOIN));
+      if (derived->nested_join)
+      {
+        derived->wrap_into_nested_join(tl->select_lex->top_join_list);
+        derived->get_unit()->exclude_level(); 
+      }
+      if (arena)
+        thd->restore_active_arena(arena, &backup);
+      derived->merged= TRUE;
+      if (!derived->nested_join)
+        return TRUE;
+    }      
+  }
+  else
+  {
+    if (!derived->merged_for_insert && mysql_derived_merge(thd, lex, derived))
+      return TRUE;
+  }
+  derived->merged_for_insert= TRUE;
+
+  return FALSE;
+}
+
+
+/*
+  @brief
+  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
+*/
+
+
+bool mysql_derived_init(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  SELECT_LEX_UNIT *unit= derived->get_unit();
+  DBUG_ENTER("mysql_derived_init");
 
+  // Skip already prepared views/DT
+  if (!unit || unit->prepared)
+    DBUG_RETURN(FALSE);
+
+  DBUG_RETURN(derived->init_derived(thd, TRUE));
+}
+
+
+/*
+  @brief
+  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().
 
@@ -114,202 +579,359 @@ out:
   the state of privilege checking (GRANT_INFO struct) is copied as-is to the
   temporary table.
 
-  This function implements a signature called "derived table processor", and
-  is passed as a function pointer to mysql_handle_derived().
+  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_filling(), GRANT_INFO
+  @see mysql_handle_derived(), mysql_derived_fill(), GRANT_INFO
 
   @return
     false  OK
     true   Error
 */
 
-bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *orig_table_list)
+bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived)
 {
-  SELECT_LEX_UNIT *unit= orig_table_list->derived;
-  ulonglong create_options;
+  SELECT_LEX_UNIT *unit= derived->get_unit();
   DBUG_ENTER("mysql_derived_prepare");
   bool res= FALSE;
-  if (unit)
-  {
-    SELECT_LEX *first_select= unit->first_select();
-    TABLE *table= 0;
-    select_union *derived_result;
 
-    /* prevent name resolving out of derived table */
-    for (SELECT_LEX *sl= first_select; sl; sl= sl->next_select())
-      sl->context.outer_context= 0;
+  // Skip already prepared views/DT
+  if (!unit || unit->prepared)
+    DBUG_RETURN(FALSE);
 
-    if (!(derived_result= new select_union))
-      DBUG_RETURN(TRUE); // out of memory
+  /* It's a target view for an INSERT, create field translation only. */
+  if (derived->merged_for_insert)
+  {
+    res= derived->create_field_translation(thd);
+    DBUG_RETURN(res);
+  }
 
-    // st_select_lex_unit::prepare correctly work for single select
-    if ((res= unit->prepare(thd, derived_result, 0)))
-      goto exit;
+  Query_arena *arena= thd->stmt_arena, backup;
+  if (arena->is_conventional())
+    arena= 0;                                   // For easier test
+  else
+    thd->set_n_backup_active_arena(arena, &backup);
 
-    if ((res= check_duplicate_names(unit->types, 0)))
-      goto exit;
+  SELECT_LEX *first_select= unit->first_select();
 
-    create_options= (first_select->options | thd->options |
-                     TMP_TABLE_ALL_COLUMNS);
-    /*
-      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_union &&
-      !unit->union_distinct->next_select() (i.e. it is union and last distinct
-      SELECT is last SELECT of UNION).
-    */
-    if ((res= derived_result->create_result_table(thd, &unit->types, FALSE,
-                                                 create_options,
-                                                 orig_table_list->alias,
-                                                 FALSE)))
-      goto exit;
+  /* prevent name resolving out of derived table */
+  for (SELECT_LEX *sl= first_select; sl; sl= sl->next_select())
+  {
+    sl->context.outer_context= 0;
+    // Prepare underlying views/DT first.
+    sl->handle_derived(lex, DT_PREPARE);
+  }
 
-    table= derived_result->table;
+  unit->derived= derived;
+
+  if (!(derived->derived_result= new select_union))
+    DBUG_RETURN(TRUE); // out of memory
+
+  // st_select_lex_unit::prepare correctly work for single select
+  if ((res= unit->prepare(thd, derived->derived_result, 0)))
+    goto exit;
+
+  if ((res= check_duplicate_names(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->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_union &&
+    !unit->union_distinct->next_select() (i.e. it is union and last distinct
+    SELECT is last SELECT of UNION).
+  */
+  if (derived->derived_result->create_result_table(thd, &unit->types, FALSE,
+                                                (first_select->options |
+                                                 thd->options |
+                                                 TMP_TABLE_ALL_COLUMNS),
+                                                derived->alias,
+                                                FALSE, FALSE))
+    goto exit;
+
+  derived->table= derived->derived_result->table;
+  if (derived->is_derived() && derived->is_merged_derived())
+    first_select->mark_as_belong_to_derived(derived);
 
 exit:
-    /* Hide "Unknown column" or "Unknown function" error */
-    if (orig_table_list->view)
-    {
-      if (thd->is_error() &&
+  /* Hide "Unknown column" or "Unknown function" error */
+  if (derived->view)
+  {
+    if (thd->is_error() &&
           (thd->main_da.sql_errno() == ER_BAD_FIELD_ERROR ||
-          thd->main_da.sql_errno() == ER_FUNC_INEXISTENT_NAME_COLLISION ||
-          thd->main_da.sql_errno() == ER_SP_DOES_NOT_EXIST))
-      {
-        thd->clear_error();
-        my_error(ER_VIEW_INVALID, MYF(0), orig_table_list->db,
-                 orig_table_list->table_name);
-      }
-    }
-
-    /*
-      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)
+           thd->main_da.sql_errno() == ER_FUNC_INEXISTENT_NAME_COLLISION ||
+           thd->main_da.sql_errno() == ER_SP_DOES_NOT_EXIST))
     {
-      if (table)
-	free_tmp_table(thd, table);
-      delete derived_result;
+      thd->clear_error();
+      my_error(ER_VIEW_INVALID, MYF(0), derived->db,
+               derived->table_name);
     }
+  }
+
+  /*
+    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->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= NON_TRANSACTIONAL_TMP_TABLE;
+#ifndef NO_EMBEDDED_ACCESS_CHECKS
+    if (derived->referencing_view)
+      table->grant= derived->grant;
     else
     {
-      if (!thd->fill_derived_tables())
-      {
-	delete derived_result;
-	derived_result= NULL;
-      }
-      orig_table_list->derived_result= derived_result;
-      orig_table_list->table= table;
-      orig_table_list->table_name=        table->s->table_name.str;
-      orig_table_list->table_name_length= table->s->table_name.length;
-      table->derived_select_number= first_select->select_number;
-      table->s->tmp_table= NON_TRANSACTIONAL_TMP_TABLE;
-#ifndef NO_EMBEDDED_ACCESS_CHECKS
-      if (orig_table_list->referencing_view)
-        table->grant= orig_table_list->grant;
-      else
-        table->grant.privilege= SELECT_ACL;
-#endif
-      orig_table_list->db= (char *)"";
-      orig_table_list->db_length= 0;
-      // Force read of table stats in the optimizer
-      table->file->info(HA_STATUS_VARIABLE);
-      /* Add new temporary table to list of open derived tables */
-      table->next= thd->derived_tables;
-      thd->derived_tables= table;
+      table->grant.privilege= SELECT_ACL;
+      if (derived->is_derived())
+        derived->grant.privilege= SELECT_ACL;
     }
+#endif
+    /* Add new temporary table to list of open derived tables */
+    table->next= thd->derived_tables;
+    thd->derived_tables= table;
   }
-  else if (orig_table_list->merge_underlying_list)
-    orig_table_list->set_underlying_merge();
+  if (arena)
+    thd->restore_active_arena(arena, &backup);
   DBUG_RETURN(res);
 }
 
 
-/*
-  fill derived table
-
-  SYNOPSIS
-    mysql_derived_filling()
-    thd			Thread handle
-    lex                 LEX for this thread
-    unit                node that contains all SELECT's for derived tables
-    orig_table_list     TABLE_LIST for the upper SELECT
-
-  IMPLEMENTATION
-    Derived table is resolved with temporary table. It is created based on the
-    queries defined. After temporary table is filled, if this is not EXPLAIN,
-    then 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.
-    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
-    TRUE   Error
+/**
+  @brief
+  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.
 */
 
-bool mysql_derived_filling(THD *thd, LEX *lex, TABLE_LIST *orig_table_list)
+bool mysql_derived_optimize(THD *thd, LEX *lex, TABLE_LIST *derived)
 {
-  TABLE *table= orig_table_list->table;
-  SELECT_LEX_UNIT *unit= orig_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;
 
-  /*check that table creation pass without problem and it is derived table */
-  if (table && unit)
+  if (unit->optimized && !unit->uncacheable && !unit->describe)
+    return FALSE;
+  lex->current_select= first_select;
+
+  if (unit->is_union())
   {
-    SELECT_LEX *first_select= unit->first_select();
-    select_union *derived_result= orig_table_list->derived_result;
-    SELECT_LEX *save_current_select= lex->current_select;
-    if (unit->is_union())
+    // optimize union without execution
+    res= unit->optimize();
+  }
+  else if (unit->derived)
+  {
+    if (!derived->is_merged_derived())
     {
-      // execute union without clean up
-      res= unit->exec();
+      unit->optimized= TRUE;
+      if ((res= first_select->join->optimize()))
+        goto err;
     }
-    else
+  }
+  /*
+    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())
     {
-      unit->set_limit(first_select);
-      if (unit->select_limit_cnt == HA_POS_ERROR)
-	first_select->options&= ~OPTION_FOUND_ROWS;
-
-      lex->current_select= first_select;
-      res= mysql_select(thd, &first_select->ref_pointer_array,
-			(TABLE_LIST*) first_select->table_list.first,
-			first_select->with_wild,
-			first_select->item_list, first_select->where,
-			(first_select->order_list.elements+
-			 first_select->group_list.elements),
-			(ORDER *) first_select->order_list.first,
-			(ORDER *) first_select->group_list.first,
-			first_select->having, (ORDER*) NULL,
-			(first_select->options | thd->options |
-			 SELECT_NO_UNLOCK),
-			derived_result, unit, first_select);
+      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;
+  return res;
+}
 
-    if (!res)
-    {
-      /*
-        Here we entirely fix both TABLE_LIST and list of SELECT's as
-        there were no derived tables
-      */
-      if (derived_result->flush())
-        res= TRUE;
-
-      if (!lex->describe)
-        unit->cleanup();
-    }
-    else
-      unit->cleanup();
-    lex->current_select= save_current_select;
+
+/**
+  @brief
+  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.
+*/
+
+bool mysql_derived_create(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  TABLE *table= derived->table;
+  SELECT_LEX_UNIT *unit= derived->get_unit();
+
+  if (table->created)
+    return FALSE;
+  select_union *result= (select_union*)unit->result;
+  if (table->s->db_type() == TMP_ENGINE_HTON)
+  {
+    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->options | TMP_TABLE_ALL_COLUMNS)))
+      return(TRUE);
   }
+  if (open_tmp_table(table))
+    return TRUE;
+  table->file->extra(HA_EXTRA_WRITE_CACHE);
+  table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
+  return FALSE;
+}
+
+
+/*
+  @brief
+  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,
+  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
+*/
+
+bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  TABLE *table= derived->table;
+  SELECT_LEX_UNIT *unit= derived->get_unit();
+  bool res= FALSE;
+
+  if (unit->executed && !unit->uncacheable && !unit->describe)
+    return FALSE;
+  /*check that table creation passed without problems. */
+  DBUG_ASSERT(table && table->created);
+  SELECT_LEX *first_select= unit->first_select();
+  select_union *derived_result= derived->derived_result;
+  SELECT_LEX *save_current_select= lex->current_select;
+  if (unit->is_union())
+  {
+    // execute union without clean up
+    res= unit->exec();
+  }
+  else
+  {
+    unit->set_limit(first_select);
+    if (unit->select_limit_cnt == HA_POS_ERROR)
+      first_select->options&= ~OPTION_FOUND_ROWS;
+
+    lex->current_select= first_select;
+    res= mysql_select(thd, &first_select->ref_pointer_array,
+                      (TABLE_LIST*) first_select->table_list.first,
+                      first_select->with_wild,
+                      first_select->item_list, first_select->where,
+                      (first_select->order_list.elements+
+                       first_select->group_list.elements),
+                      (ORDER *) first_select->order_list.first,
+                      (ORDER *) first_select->group_list.first,
+                      first_select->having, (ORDER*) NULL,
+                      (first_select->options | thd->options |
+                       SELECT_NO_UNLOCK),
+                      derived_result, unit, first_select);
+  }
+
+  if (!res)
+  {
+    if (derived_result->flush())
+      res= TRUE;
+    unit->executed= TRUE;
+  }
+  if (res || !lex->describe) 
+    unit->cleanup();
+  lex->current_select= save_current_select;
+
   return res;
 }
+
+
+/**
+  @brief
+  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
+*/
+
+bool mysql_derived_reinit(THD *thd, LEX *lex, TABLE_LIST *derived)
+{
+  st_select_lex_unit *unit= derived->get_unit();
+
+  if (derived->table)
+    derived->merged_for_insert= FALSE;
+  unit->unclean();
+  unit->types.empty();
+  /* for derived tables & PS (which can't be reset by Item_subquery) */
+  unit->reinit_exec_mechanism();
+  unit->set_thd(thd);
+  return FALSE;
+}