create_options.cc

/* Copyright (C) 2010, 2020, 2021, MariaDB Corporation.

   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 Street, Fifth Floor, Boston, MA 02110-1335 USA */

/**
  @file

  Engine defined options of tables/fields/keys in CREATE/ALTER TABLE.
*/

#include "mariadb.h"
#include "create_options.h"
#include "partition_info.h"
#include <my_getopt.h>
#include "set_var.h"

#define FRM_QUOTED_VALUE 0x8000U

/**
  Links this item to the given list end

  @param start           The list beginning or NULL
  @param end             The list last element or does not matter
*/

void engine_option_value::link(engine_option_value **start,
                               engine_option_value **end)
{
  DBUG_ENTER("engine_option_value::link");
  DBUG_PRINT("enter", ("name: '%s' (%u)  value: '%s' (%u)",
                       name.str, (uint) name.length,
                       value.str, (uint) value.length));
  engine_option_value *opt;
  /* check duplicates to avoid writing them to frm*/
  for(opt= *start;
      opt && ((opt->parsed && !opt->value.str) ||
              !name.streq(opt->name));
      opt= opt->next) /* no-op */;
  if (opt)
  {
    opt->value= Value(); /* remove previous value */
    opt->parsed= TRUE;          /* and don't issue warnings for it anymore */
  }
  /*
    Add this option to the end of the list

    @note: We add even if it is opt->value.str == NULL because it can be
    ALTER TABLE to remove the option.
  */
  if (*start)
  {
    (*end)->next= this;
    *end= this;
  }
  else
  {
    /*
      note that is *start == 0, the value of *end does not matter,
      it can be uninitialized.
    */
    *start= *end= this;
  }
  DBUG_VOID_RETURN;
}

static bool report_wrong_value(THD *thd, const char *name, const char *val,
                               bool suppress_warning)
{
  if (suppress_warning)
    return 0;

  if (!(thd->variables.sql_mode & MODE_IGNORE_BAD_TABLE_OPTIONS) &&
      !thd->slave_thread)
  {
    my_error(ER_BAD_OPTION_VALUE, MYF(0), val, name);
    return 1;
  }

  push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN, ER_BAD_OPTION_VALUE,
                      ER_THD(thd, ER_BAD_OPTION_VALUE), val, name);
  return 0;
}

static bool report_unknown_option(THD *thd, engine_option_value *val,
                                  bool suppress_warning)
{
  DBUG_ENTER("report_unknown_option");

  if (val->parsed || suppress_warning || thd->slave_thread)
  {
    DBUG_PRINT("info", ("parsed => exiting"));
    DBUG_RETURN(FALSE);
  }

  if (!(thd->variables.sql_mode & MODE_IGNORE_BAD_TABLE_OPTIONS))
  {
    my_error(ER_UNKNOWN_OPTION, MYF(0), val->name.str);
    DBUG_RETURN(TRUE);
  }

  push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
                      ER_UNKNOWN_OPTION, ER_THD(thd, ER_UNKNOWN_OPTION),
                      val->name.str);
  DBUG_RETURN(FALSE);
}

#define value_ptr(STRUCT,OPT)    ((char*)(STRUCT) + (OPT)->offset)

static bool set_one_value(ha_create_table_option *opt,
                          THD *thd, const engine_option_value::Value *value,
                          void *base,
                          bool suppress_warning,
                          MEM_ROOT *root)
{
  DBUG_ENTER("set_one_value");
  DBUG_PRINT("enter", ("opt: %p type: %u name '%s' value: '%s'",
                       opt,
                       opt->type, opt->name,
                       (value->str ? value->str : "<DEFAULT>")));
  switch (opt->type)
  {
  case HA_OPTION_TYPE_SYSVAR:
    // HA_OPTION_TYPE_SYSVAR's are replaced in resolve_sysvars()
    break; // to DBUG_ASSERT(0)
  case HA_OPTION_TYPE_ULL:
    {
      ulonglong *val= (ulonglong*)value_ptr(base, opt);
      if (!value->str)
      {
        *val= opt->def_value;
        DBUG_RETURN(0);
      }

      my_option optp=
        { opt->name, 1, 0, (uchar **)val, 0, 0, GET_ULL,
          REQUIRED_ARG, (longlong)opt->def_value, (longlong)opt->min_value,
          opt->max_value, 0, (long) opt->block_size, 0};

      ulonglong orig_val= strtoull(value->str, NULL, 10);
      my_bool unused;
      *val= orig_val;
      *val= getopt_ull_limit_value(*val, &optp, &unused);
      if (*val == orig_val)
        DBUG_RETURN(0);

      DBUG_RETURN(report_wrong_value(thd, opt->name, value->str,
                                     suppress_warning));
    }
  case HA_OPTION_TYPE_STRING:
    {
      char **val= (char **)value_ptr(base, opt);
      if (!value->str)
      {
        *val= 0;
        DBUG_RETURN(0);
      }

      if (!(*val= strmake_root(root, value->str, value->length)))
        DBUG_RETURN(1);
      DBUG_RETURN(0);
    }
  case HA_OPTION_TYPE_ENUM:
    {
      uint *val= (uint *)value_ptr(base, opt), num;

      *val= (uint) opt->def_value;
      if (!value->str)
        DBUG_RETURN(0);

      const char *start= opt->values, *end;

      num= 0;
      while (*start)
      {
        for (end=start;
             *end && *end != ',';
             end++) /* no-op */;
        if (value->streq(Lex_cstring(start, end)))
        {
          *val= num;
          DBUG_RETURN(0);
        }
        if (*end)
          end++;
        start= end;
        num++;
      }

      DBUG_RETURN(report_wrong_value(thd, opt->name, value->str,
                                     suppress_warning));
    }
  case HA_OPTION_TYPE_BOOL:
    {
      bool *val= (bool *)value_ptr(base, opt);
      *val= opt->def_value;

      if (!value->str)
        DBUG_RETURN(0);

      if (value->streq("NO"_LEX_CSTRING) ||
          value->streq("OFF"_LEX_CSTRING) ||
          value->streq("0"_LEX_CSTRING))
      {
        *val= FALSE;
        DBUG_RETURN(FALSE);
      }

      if (value->streq("YES"_LEX_CSTRING) ||
          value->streq("ON"_LEX_CSTRING) ||
          value->streq("1"_LEX_CSTRING))
      {
        *val= TRUE;
        DBUG_RETURN(FALSE);
      }

      DBUG_RETURN(report_wrong_value(thd, opt->name, value->str,
                                     suppress_warning));
    }
  }
  DBUG_ASSERT(0);
  my_error(ER_UNKNOWN_ERROR, MYF(0));
  DBUG_RETURN(1);
}

static const size_t ha_option_type_sizeof[]=
{ sizeof(ulonglong), sizeof(char *), sizeof(uint), sizeof(bool)};

/**
  Creates option structure and parses list of options in it

  @param thd              thread handler
  @param option_struct    where to store pointer on the option struct
  @param option_list      list of options given by user
  @param rules            list of option description by engine
  @param suppress_warning second parse so we do not need warnings
  @param root             MEM_ROOT where allocate memory

  @retval TRUE  Error
  @retval FALSE OK
*/

bool parse_option_list(THD* thd, handlerton *hton, void *option_struct_arg,
                       engine_option_value **option_list,
                       ha_create_table_option *rules,
                       bool suppress_warning, MEM_ROOT *root)
{
  ha_create_table_option *opt;
  size_t option_struct_size= 0;
  engine_option_value *val, *last;
  void **option_struct= (void**)option_struct_arg;
  DBUG_ENTER("parse_option_list");
  DBUG_PRINT("enter",
             ("struct: %p list: %p rules: %p suppress_warning: %u root: %p",
              *option_struct, *option_list, rules,
              (uint) suppress_warning, root));

  if (rules)
  {
    for (opt= rules; opt->name; opt++)
      set_if_bigger(option_struct_size, opt->offset +
                    ha_option_type_sizeof[opt->type]);

    *option_struct= alloc_root(root, option_struct_size);
  }

  for (opt= rules; rules && opt->name; opt++)
  {
    bool seen=false;
    for (val= *option_list; val; val= val->next)
    {
      last= val;
      if (!val->name.streq(Lex_cstring(opt->name, opt->name_length)))
        continue;

      /* skip duplicates (see engine_option_value constructor above) */
      if (val->parsed && !val->value.str)
        continue;

      if (set_one_value(opt, thd, &val->value,
                        *option_struct, suppress_warning || val->parsed, root))
        DBUG_RETURN(TRUE);
      val->parsed= true;
      seen=true;
      break;
    }
    if (!seen || (opt->var && !last->value.str))
    {
      engine_option_value::Value default_val;

      /*
        Okay, here's the logic for sysvar options:
        1. When we parse CREATE TABLE and sysvar option was not explicitly
           mentioned we add it to the list as if it was specified with the
           *current* value of the underlying sysvar.
        2. But only if the underlying sysvar value is different from the
           sysvar's default.
        3. If it's ALTER TABLE or CREATE_SEQUENCE and the sysvar option was
           not explicitly mentioned - do nothing, do not add it to the list.
        4. But if it was ALTER TABLE with sysvar option = DEFAULT, we
           add it to the list (under the same condition #2).
        5. If we're here parsing the option list from the .frm file
           for a normal open_table() and the sysvar option was not there -
           do not add it to the list (makes no sense anyway) and
           use the *default* value of the underlying sysvar. Because
           sysvar value can change, but it should not affect existing tables.
        This is how it's implemented: the current sysvar value is added
        to the list if suppress_warning is FALSE (meaning a table is created,
        that is CREATE TABLE or ALTER TABLE) and it's actually a CREATE TABLE
        command or it's an ALTER TABLE and the option was seen (=DEFAULT).

        Note that if the option was set explicitly (not =DEFAULT) it wouldn't
        have passes the if() condition above.
      */
      if (!suppress_warning && opt->var &&
          (thd->lex->sql_command == SQLCOM_CREATE_TABLE || seen))
      {
        // take a value from the variable and add it to the list
        sys_var *sysvar= find_hton_sysvar(hton, opt->var);
        DBUG_ASSERT(sysvar);

        if (!sysvar->session_is_default(thd))
        {
          char buf[256];
          String sbuf(buf, sizeof(buf), system_charset_info), *str;
          if ((str= sysvar->val_str(&sbuf, thd, OPT_SESSION, &null_clex_str)))
          {
            engine_option_value::Name name(opt->name, opt->name_length);
            default_val.str= strmake_root(root, str->ptr(), str->length());
            default_val.length= str->length();
            val= new (root) engine_option_value(
                name, default_val, opt->type != HA_OPTION_TYPE_ULL);
            if (!val)
              DBUG_RETURN(TRUE);
            val->link(option_list, &last);
            val->parsed= true;
          }
        }
      }
      set_one_value(opt, thd, &default_val, *option_struct,
                    suppress_warning, root);
    }
  }

  for (val= *option_list; val; val= val->next)
  {
    if (report_unknown_option(thd, val, suppress_warning))
      DBUG_RETURN(TRUE);
    val->parsed= true;
  }

  DBUG_RETURN(FALSE);
}


/**
  Resolves all HA_OPTION_TYPE_SYSVAR elements.

  This is done when an engine is loaded.
*/
static bool resolve_sysvars(handlerton *hton, ha_create_table_option *rules)
{
  for (ha_create_table_option *opt= rules; rules && opt->name; opt++)
  {
    if (opt->type == HA_OPTION_TYPE_SYSVAR)
    {
      struct my_option optp;
      plugin_opt_set_limits(&optp, opt->var);
      switch(optp.var_type) {
      case GET_ULL:
      case GET_ULONG:
      case GET_UINT:
        opt->type= HA_OPTION_TYPE_ULL;
        opt->def_value= (ulonglong)optp.def_value;
        opt->min_value= (ulonglong)optp.min_value;
        opt->max_value= (ulonglong)optp.max_value;
        opt->block_size= (ulonglong)optp.block_size;
        break;
      case GET_STR:
      case GET_STR_ALLOC:
        opt->type= HA_OPTION_TYPE_STRING;
        break;
      case GET_BOOL:
        opt->type= HA_OPTION_TYPE_BOOL;
        opt->def_value= optp.def_value;
        break;
      case GET_ENUM:
      {
        opt->type= HA_OPTION_TYPE_ENUM;
        opt->def_value= optp.def_value;

        char buf[256];
        String str(buf, sizeof(buf), system_charset_info);
        str.length(0);
        for (const char **s= optp.typelib->type_names; *s; s++)
        {
          if (str.append(*s, strlen(*s)) || str.append(','))
            return 1;
        }
        DBUG_ASSERT(str.length());
        opt->values= my_strndup(PSI_INSTRUMENT_ME, str.ptr(), str.length()-1, MYF(MY_WME));
        if (!opt->values)
          return 1;
        break;
      }
      default:
        DBUG_ASSERT(0);
      }
    }
  }
  return 0;
}

bool resolve_sysvar_table_options(handlerton *hton)
{
  return resolve_sysvars(hton, hton->table_options) ||
         resolve_sysvars(hton, hton->field_options) ||
         resolve_sysvars(hton, hton->index_options);
}

/*
  Restore HA_OPTION_TYPE_SYSVAR options back as they were
  before resolve_sysvars().

  This is done when the engine is unloaded, so that we could
  call resolve_sysvars() if the engine is installed again.
*/
static void free_sysvars(handlerton *hton, ha_create_table_option *rules)
{
  for (ha_create_table_option *opt= rules; rules && opt->name; opt++)
  {
    if (opt->var)
    {
      my_free(const_cast<char*>(opt->values));
      opt->type= HA_OPTION_TYPE_SYSVAR;
      opt->def_value= 0;
      opt->min_value= 0;
      opt->max_value= 0;
      opt->block_size= 0;
      opt->values= 0;
    }
  }
}

void free_sysvar_table_options(handlerton *hton)
{
  free_sysvars(hton, hton->table_options);
  free_sysvars(hton, hton->field_options);
  free_sysvars(hton, hton->index_options);
}


/**
  Parses all table/fields/keys options

  @param thd             thread handler
  @param file            handler of the table
  @parem share           descriptor of the table

  @retval TRUE  Error
  @retval FALSE OK
*/

bool parse_engine_table_options(THD *thd, handlerton *ht, TABLE_SHARE *share)
{
  MEM_ROOT *root= &share->mem_root;
  DBUG_ENTER("parse_engine_table_options");

  if (parse_option_list(thd, ht, &share->option_struct, & share->option_list,
                        ht->table_options, TRUE, root))
    DBUG_RETURN(TRUE);

  for (Field **field= share->field; *field; field++)
  {
    if (parse_option_list(thd, ht, &(*field)->option_struct,
                          & (*field)->option_list,
                          ht->field_options, TRUE, root))
      DBUG_RETURN(TRUE);
  }

  for (uint index= 0; index < share->keys; index ++)
  {
    if (parse_option_list(thd, ht, &share->key_info[index].option_struct,
                          & share->key_info[index].option_list,
                          ht->index_options, TRUE, root))
      DBUG_RETURN(TRUE);
  }

  DBUG_RETURN(FALSE);
}

#ifdef WITH_PARTITION_STORAGE_ENGINE
/**
  Parses engine-defined partition options

  @param [in] thd   thread handler
  @parem [in] table table with part_info

  @retval TRUE  Error
  @retval FALSE OK

  In the case of ALTER TABLE statements, table->part_info is set up
  by mysql_unpack_partition(). So, one should not call the present
  function before the call of mysql_unpack_partition().
*/
bool parse_engine_part_options(THD *thd, TABLE *table)
{
  MEM_ROOT *root= &table->mem_root;
  TABLE_SHARE *share= table->s;
  partition_info *part_info= table->part_info;
  engine_option_value *tmp_option_list;
  handlerton *ht;
  DBUG_ENTER("parse_engine_part_options");

  if (!part_info)
    DBUG_RETURN(FALSE);

  List_iterator<partition_element> it(part_info->partitions);
  while (partition_element *part_elem= it++)
  {
    if (merge_engine_options(share->option_list, part_elem->option_list,
                             &tmp_option_list, root))
      DBUG_RETURN(TRUE);

    if (!part_info->is_sub_partitioned())
    {
      ht= part_elem->engine_type;
      if (parse_option_list(thd, ht, &part_elem->option_struct,
                            &tmp_option_list, ht->table_options, TRUE, root))
        DBUG_RETURN(TRUE);
    }
    else
    {
      List_iterator<partition_element> sub_it(part_elem->subpartitions);
      while (partition_element *sub_part_elem= sub_it++)
      {
        ht= sub_part_elem->engine_type;
        if (parse_option_list(thd, ht, &sub_part_elem->option_struct,
                              &tmp_option_list, ht->table_options, TRUE, root))
          DBUG_RETURN(TRUE);
      }
    }
  }
  DBUG_RETURN(FALSE);
}
#endif

bool engine_options_differ(void *old_struct, void *new_struct,
                           ha_create_table_option *rules)
{
  ha_create_table_option *opt;
  for (opt= rules; rules && opt->name; opt++)
  {
    char **old_val= (char**)value_ptr(old_struct, opt);
    char **new_val= (char**)value_ptr(new_struct, opt);
    int neq;
    if (opt->type == HA_OPTION_TYPE_STRING)
      neq= (*old_val && *new_val) ? strcmp(*old_val, *new_val) :  *old_val != *new_val;
    else
      neq= memcmp(old_val, new_val, ha_option_type_sizeof[opt->type]);
    if (neq)
      return true;
  }
  return false;
}


/**
  Returns representation length of key and value in the frm file
*/

uint engine_option_value::frm_length()
{
  /*
    1 byte  - name length
    2 bytes - value length

    if value.str is NULL, this option is not written to frm (=DEFAULT)
  */
  return value.str ? (uint)(1 + name.length + 2 + value.length) : 0;
}


/**
  Returns length of representation of option list in the frm file
*/

static uint option_list_frm_length(engine_option_value *opt)
{
  uint res= 0;

  for (; opt; opt= opt->next)
    res+= opt->frm_length();

  return res;
}


/**
  Calculates length of options image in the .frm

  @param table_option_list list of table options
  @param create_fields     field descriptors list
  @param keys              number of keys
  @param key_info          array of key descriptors

  @returns length of image in frm
*/

uint engine_table_options_frm_length(engine_option_value *table_option_list,
                                     List<Create_field> &create_fields,
                                     uint keys, KEY *key_info)
{
  List_iterator<Create_field> it(create_fields);
  Create_field *field;
  uint res, index;
  DBUG_ENTER("engine_table_options_frm_length");

  res= option_list_frm_length(table_option_list);

  while ((field= it++))
    res+= option_list_frm_length(field->option_list);

  for (index= 0; index < keys; index++, key_info++)
    res+= option_list_frm_length(key_info->option_list);

  /*
    if there's at least one option somewhere (res > 0)
    we write option lists for all fields and keys, zero-terminated.
    If there're no options we write nothing at all (backward compatibility)
  */
  DBUG_RETURN(res ? res + 1 + create_fields.elements + keys : 0);
}


/**
  Writes image of the key and value to the frm image buffer

  @param buff            pointer to the buffer free space beginning

  @returns pointer to byte after last recorded in the buffer
*/

uchar *engine_option_value::frm_image(uchar *buff)
{
  if (value.str)
  {
    DBUG_ASSERT(name.length <= 0xff);
    *buff++= (uchar)name.length;
    memcpy(buff, name.str, name.length);
    buff+= name.length;
    int2store(buff, value.length | (quoted_value ? FRM_QUOTED_VALUE : 0));
    buff+= 2;
    memcpy(buff, (const uchar *) value.str, value.length);
    buff+= value.length;
  }
  return buff;
}

/**
  Writes image of the key and value to the frm image buffer

  @param buff            pointer to the buffer to store the options in
  @param opt             list of options;

  @returns pointer to the end of the stored data in the buffer
*/
static uchar *option_list_frm_image(uchar *buff, engine_option_value *opt)
{
  for (; opt; opt= opt->next)
    buff= opt->frm_image(buff);

  *buff++= 0;
  return buff;
}


/**
  Writes options image in the .frm buffer

  @param buff              pointer to the buffer
  @param table_option_list list of table options
  @param create_fields     field descriptors list
  @param keys              number of keys
  @param key_info          array of key descriptors

  @returns pointer to byte after last recorded in the buffer
*/

uchar *engine_table_options_frm_image(uchar *buff,
                                      engine_option_value *table_option_list,
                                      List<Create_field> &create_fields,
                                      uint keys, KEY *key_info)
{
  List_iterator<Create_field> it(create_fields);
  Create_field *field;
  KEY *key_info_end= key_info + keys;
  DBUG_ENTER("engine_table_options_frm_image");

  buff= option_list_frm_image(buff, table_option_list);

  while ((field= it++))
    buff= option_list_frm_image(buff, field->option_list);

  while (key_info < key_info_end)
    buff= option_list_frm_image(buff, (key_info++)->option_list);

  DBUG_RETURN(buff);
}

/**
  Reads name and value from buffer, then link it in the list

  @param buff            the buffer to read from
  @param start           The list beginning or NULL
  @param end             The list last element or does not matter
  @param root            MEM_ROOT for allocating

  @returns pointer to byte after last recorded in the buffer
*/
uchar *engine_option_value::frm_read(const uchar *buff, const uchar *buff_end,
                                     engine_option_value **start,
                                     engine_option_value **end, MEM_ROOT *root)
{
  LEX_CSTRING name, value;
  uint len;
#define need_buff(N)  if (buff + (N) >= buff_end) return NULL

  need_buff(3);
  name.length= buff[0];
  buff++;
  need_buff(name.length + 2);
  if (!(name.str= strmake_root(root, (const char*)buff, name.length)))
    return NULL;
  buff+= name.length;
  len= uint2korr(buff);
  value.length= len & ~FRM_QUOTED_VALUE;
  buff+= 2;
  need_buff(value.length);
  if (!(value.str= strmake_root(root, (const char*)buff, value.length)))
    return NULL;
  buff+= value.length;

  engine_option_value *ptr=
      new (root) engine_option_value(engine_option_value::Name(name),
                                     engine_option_value::Value(value),
                                     len & FRM_QUOTED_VALUE);
  if (!ptr)
    return NULL;
  ptr->link(start, end);

  return (uchar *)buff;
}


/**
  Reads options from this buffer

  @param buff            the buffer to read from
  @param length          buffer length
  @param share           table descriptor
  @param root            MEM_ROOT for allocating

  @retval TRUE  Error
  @retval FALSE OK
*/

bool engine_table_options_frm_read(const uchar *buff, size_t length,
                                   TABLE_SHARE *share)
{
  const uchar *buff_end= buff + length;
  engine_option_value *UNINIT_VAR(end);
  MEM_ROOT *root= &share->mem_root;
  uint count;
  DBUG_ENTER("engine_table_options_frm_read");

  while (buff < buff_end && *buff)
  {
    if (!(buff= engine_option_value::frm_read(buff, buff_end,
                                              &share->option_list, &end, root)))
      DBUG_RETURN(TRUE);
  }
  buff++;

  for (count=0; count < share->fields; count++)
  {
    while (buff < buff_end && *buff)
    {
      if (!(buff= engine_option_value::frm_read(buff, buff_end,
                                                &share->field[count]->option_list,
                                                &end, root)))
        DBUG_RETURN(TRUE);
    }
    buff++;
  }

  for (count=0; count < share->keys; count++)
  {
    while (buff < buff_end && *buff)
    {
      if (!(buff= engine_option_value::frm_read(buff, buff_end,
                                                &share->key_info[count].option_list,
                                                &end, root)))
        DBUG_RETURN(TRUE);
    }
    buff++;
  }

  if (buff < buff_end)
    sql_print_warning("Table '%s' was created in a later MariaDB version - "
                      "unknown table attributes were ignored",
                      share->table_name.str);

  DBUG_RETURN(buff > buff_end);
}

/**
  Merges two lists of engine_option_value's with duplicate removal.

  @param [in] source  option list
  @param [in] changes option list whose options overwrite source's
  @param [out] out    new option list created by merging given two
  @param [in] root    MEM_ROOT for allocating memory

  @retval TRUE  Error
  @retval FALSE OK
*/
bool merge_engine_options(engine_option_value *source,
                          engine_option_value *changes,
                          engine_option_value **out, MEM_ROOT *root)
{
  engine_option_value *UNINIT_VAR(end), *opt, *opt_copy;
  *out= 0;
  DBUG_ENTER("merge_engine_options");

  /* Create copy of source list */
  for (opt= source; opt; opt= opt->next)
  {
    opt_copy= new (root) engine_option_value(opt);
    if (!opt_copy)
      DBUG_RETURN(TRUE);
    opt_copy->link(out, &end);
  }

  for (opt= changes; opt; opt= opt->next)
  {
    opt_copy= new (root) engine_option_value(opt);
    if (!opt_copy)
      DBUG_RETURN(TRUE);
    opt_copy->link(out, &end);
  }
  DBUG_RETURN(FALSE);
}

bool is_engine_option_known(engine_option_value *opt,
                            ha_create_table_option *rules)
{
  if (!rules)
    return false;

  for (; rules->name; rules++)
  {
      if (opt->name.streq(Lex_cstring(rules->name, rules->name_length)))
        return true;
  }
  return false;
}