sql_derived.cc

/* Copyright (c) 2002, 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,
   51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA */


/*
  Derived tables
  These were introduced by Sinisa <sinisa@mysql.com>
*/


#include "my_global.h"                          /* NO_EMBEDDED_ACCESS_CHECKS */
#include "sql_priv.h"
#include "unireg.h"
#include "sql_derived.h"
#include "sql_select.h"
#include "sql_optimizer.h"                    // JOIN
#include "sql_view.h"                         // check_duplicate_names
#include "sql_acl.h"                          // SELECT_ACL
#include "sql_tmp_table.h"                    // Tmp tables


bool
mysql_handle_derived(LEX *lex, bool (*processor)(THD*, LEX*, TABLE_LIST*))
{
  bool res= FALSE;
  if (lex->derived_tables)
  {
    lex->thd->derived_tables_processing= TRUE;
    for (SELECT_LEX *sl= lex->all_selects_list;
         sl;
         sl= sl->next_select_in_list())
    {
      for (TABLE_LIST *table_ref= sl->get_table_list();
           table_ref;
           table_ref= table_ref->next_local)
      {
        if ((res= mysql_handle_single_derived(lex, table_ref, processor)))
          goto out;
      }
      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;
      }
    }
  }
out:
  lex->thd->derived_tables_processing= FALSE;
  return res;
}


bool
mysql_handle_single_derived(LEX *lex, TABLE_LIST *derived,
                            bool (*processor)(THD*, LEX*, TABLE_LIST*))
{
  return (derived->is_view_or_derived() &&
          (*processor)(lex->thd, lex, derived));
}

bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived)
{
  SELECT_LEX_UNIT *unit= derived->get_unit();
  ulonglong create_options;
  DBUG_ENTER("mysql_derived_prepare");
  bool res= FALSE;
  DBUG_ASSERT(unit);
  if (derived->uses_materialization())
  {
    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;

    if (!(derived_result= new select_union))
      DBUG_RETURN(TRUE); // out of memory

    lex->context_analysis_only|= CONTEXT_ANALYSIS_ONLY_DERIVED;
    // st_select_lex_unit::prepare correctly work for single select
    if ((res= unit->prepare(thd, derived_result, 0)))
      goto exit;
    lex->context_analysis_only&= ~CONTEXT_ANALYSIS_ONLY_DERIVED;
    if ((res= check_duplicate_names(unit->types, 0)))
      goto exit;

    create_options= (first_select->options | thd->variables.option_bits |
                     TMP_TABLE_ALL_COLUMNS);
    /*
      Temp table is created so that it honors 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,
                                                 derived->alias, FALSE, FALSE)))
      goto exit;

    table= derived_result->table;

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,
                 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 (table)
        free_tmp_table(thd, table);
      delete derived_result;
    }
    else
    {
      derived->derived_result= derived_result;
      derived->table= table;
      derived->table_name=        table->s->table_name.str;
      derived->table_name_length= table->s->table_name.length;
      table->s->tmp_table= NON_TRANSACTIONAL_TMP_TABLE;
#ifndef NO_EMBEDDED_ACCESS_CHECKS
      if (derived->referencing_view)
        table->grant= derived->grant;
      else
        table->grant.privilege= SELECT_ACL;
#endif
      derived->db= (char *)"";
      derived->db_length= 0;
      /* Add new temporary table to list of open derived tables */
      table->next= thd->derived_tables;
      thd->derived_tables= table;
    }
  }
  else
    derived->set_underlying_merge();
  DBUG_RETURN(res);
}


bool mysql_derived_optimize(THD *thd, LEX *lex, TABLE_LIST *derived)
{
  SELECT_LEX_UNIT *unit= derived->get_unit();
  DBUG_ENTER("mysql_derived_optimize");

  DBUG_ASSERT(unit);

  // optimize union without execution
  if (unit->optimize() || thd->is_error())
    DBUG_RETURN(TRUE);

  if (derived->materializable_is_const() &&
      (mysql_derived_create(thd, lex, derived) ||
       mysql_derived_materialize(thd, lex, derived)))
    DBUG_RETURN(TRUE);

  DBUG_RETURN(FALSE);
}


bool mysql_derived_create(THD *thd, LEX *lex, TABLE_LIST *derived)
{
  TABLE *table= derived->table;
  SELECT_LEX_UNIT *unit= derived->get_unit();
  DBUG_ENTER("mysql_derived_create");

  DBUG_ASSERT(unit);

  /*
   Don't create result table in following cases:
   *) It's a mergeable view.
   *) Some commands, like show table status, doesn't prepare views/derived
      tables => no need to create result table also.
   *) Table is already created.
   *) Table is a constant one with all NULL values.
  */
  if (!derived->uses_materialization() || !table || table->is_created() ||
      (derived->select_lex->join != NULL &&
       (derived->select_lex->join->const_table_map & table->map)))
  {
    /*
      At this point, JT_CONST derived tables should be null rows. Otherwise they
      would have been materialized already.
    */
    DBUG_ASSERT(table == NULL || table->reginfo.join_tab == NULL ||
                table->reginfo.join_tab->type != JT_CONST ||
                table->null_row == 1);
    DBUG_RETURN(FALSE);
  }
  /* create tmp table */
  select_union *result= (select_union*)unit->get_result();

  if (instantiate_tmp_table(table, table->key_info,
                            result->tmp_table_param.start_recinfo,
                            &result->tmp_table_param.recinfo,
                            (unit->first_select()->options |
                             thd->lex->select_lex.options |
                             thd->variables.option_bits |
                             TMP_TABLE_ALL_COLUMNS),
                            thd->variables.big_tables, &thd->opt_trace))
    DBUG_RETURN(TRUE);

  table->file->extra(HA_EXTRA_WRITE_CACHE);
  table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);

  table->set_created();

  DBUG_RETURN(FALSE);
}


bool mysql_derived_materialize(THD *thd, LEX *lex, TABLE_LIST *derived)
{
  SELECT_LEX_UNIT *unit= derived->get_unit();
  bool res= FALSE;
  DBUG_ENTER("mysql_derived_materialize");

  DBUG_ASSERT(unit && derived->table && derived->table->is_created());

  select_union *derived_result= derived->derived_result;

  if (unit->is_union())
  {
    // execute union without clean up
    res= unit->exec();
  }
  else
  {
    SELECT_LEX *first_select= unit->first_select();
    JOIN *join= first_select->join;
    SELECT_LEX *save_current_select= lex->current_select;
    lex->current_select= first_select;

    DBUG_ASSERT(join && join->optimized);

    unit->set_limit(first_select);
    if (unit->select_limit_cnt == HA_POS_ERROR)
      first_select->options&= ~OPTION_FOUND_ROWS;

    join->exec();
    res= join->error;
    lex->current_select= save_current_select;
  }

  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;
  }

  DBUG_RETURN(res);
}


bool mysql_derived_cleanup(THD *thd, LEX *lex, TABLE_LIST *derived)
{
  DBUG_ENTER("mysql_derived_cleanup");
  SELECT_LEX_UNIT *unit= derived->derived;
  if (unit)
    unit->cleanup();
  DBUG_RETURN(false);
}