mariadb/sql/sql_prepare.cc

/* Copyright (C) 1995-2002 MySQL AB

   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; either version 2 of the License, or
   (at your option) any later version.

   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA */

/**********************************************************************
This file contains the implementation of prepare and executes.

Prepare:

  - Server gets the query from client with command 'COM_STMT_PREPARE';
    in the following format:
    [COM_STMT_PREPARE:1] [query]
  - Parse the query and recognize any parameter markers '?' and
    store its information list in lex->param_list
  - Allocate a new statement for this prepare; and keep this in
    'thd->prepared_statements' pool.
  - Without executing the query, return back to client the total
    number of parameters along with result-set metadata information
    (if any) in the following format:
    [STMT_ID:4]
    [Column_count:2]
    [Param_count:2]
    [Columns meta info] (if Column_count > 0)
    [Params meta info]  (if Param_count > 0 ) (TODO : 4.1.1)

Prepare-execute:

  - Server gets the command 'COM_STMT_EXECUTE' to execute the
    previously prepared query. If there is any param markers; then client
    will send the data in the following format:
    [COM_STMT_EXECUTE:1]
    [STMT_ID:4]
    [NULL_BITS:(param_count+7)/8)]
    [TYPES_SUPPLIED_BY_CLIENT(0/1):1]
    [[length]data]
    [[length]data] .. [[length]data].
    (Note: Except for string/binary types; all other types will not be
    supplied with length field)
  - Replace the param items with this new data. If it is a first execute
    or types altered by client; then setup the conversion routines.
  - Execute the query without re-parsing and send back the results
    to client

Long data handling:

  - Server gets the long data in pieces with command type
    'COM_STMT_SEND_LONG_DATA'.
  - The packet recieved will have the format as:
    [COM_STMT_SEND_LONG_DATA:1][STMT_ID:4][parameter_number:2][data]
  - data from the packet is appended to long data value buffer for this
    placeholder.
  - It's up to the client to check for read data ended. The server doesn't
    care; and also server doesn't notify to the client that it got the
    data or not; if there is any error; then during execute; the error
    will be returned

***********************************************************************/

#include "mysql_priv.h"
#include "sql_select.h" // for JOIN
#include <m_ctype.h>  // for isspace()
#include "sp_head.h"
#include "sp.h"
#ifdef EMBEDDED_LIBRARY
/* include MYSQL_BIND headers */
#include <mysql.h>
#else
#include <mysql_com.h>
#endif

/******************************************************************************
  Prepared_statement: statement which can contain placeholders
******************************************************************************/

class Prepared_statement: public Statement
{
public:
  THD *thd;
  Item_param **param_array;
  uint param_count;
  uint last_errno;
  char last_error[MYSQL_ERRMSG_SIZE];
#ifndef EMBEDDED_LIBRARY
  bool (*set_params)(Prepared_statement *st, uchar *data, uchar *data_end,
                     uchar *read_pos, String *expanded_query);
#else
  bool (*set_params_data)(Prepared_statement *st, String *expanded_query);
#endif
  bool (*set_params_from_vars)(Prepared_statement *stmt,
                               List<LEX_STRING>& varnames,
                               String *expanded_query);
public:
  Prepared_statement(THD *thd_arg);
  virtual ~Prepared_statement();
  void setup_set_params();
  virtual Query_arena::Type type() const;
  virtual void close_cursor();
};

static void execute_stmt(THD *thd, Prepared_statement *stmt,
                         String *expanded_query);

/******************************************************************************
  Implementation
******************************************************************************/


inline bool is_param_null(const uchar *pos, ulong param_no)
{
  return pos[param_no/8] & (1 << (param_no & 7));
}

enum { STMT_QUERY_LOG_LENGTH= 8192 };

/*
  Seek prepared statement in statement map by id: returns zero if statement
  was not found, pointer otherwise.
*/

static Prepared_statement *
find_prepared_statement(THD *thd, ulong id, const char *where)
{
  Statement *stmt= thd->stmt_map.find(id);

  if (stmt == 0 || stmt->type() != Query_arena::PREPARED_STATEMENT)
  {
    char llbuf[22];
    my_error(ER_UNKNOWN_STMT_HANDLER, MYF(0), sizeof(llbuf), llstr(id, llbuf),
             where);
    return 0;
  }
  return (Prepared_statement *) stmt;
}


/*
  Send prepared stmt info to client after prepare
*/

#ifndef EMBEDDED_LIBRARY
static bool send_prep_stmt(Prepared_statement *stmt, uint columns)
{
  NET *net= &stmt->thd->net;
  char buff[12];
  uint tmp;
  DBUG_ENTER("send_prep_stmt");

  buff[0]= 0;                                   /* OK packet indicator */
  int4store(buff+1, stmt->id);
  int2store(buff+5, columns);
  int2store(buff+7, stmt->param_count);
  buff[9]= 0;                                   // Guard against a 4.1 client
  tmp= min(stmt->thd->total_warn_count, 65535);
  int2store(buff+10, tmp);

  /*
    Send types and names of placeholders to the client
    XXX: fix this nasty upcast from List<Item_param> to List<Item>
  */
  DBUG_RETURN(my_net_write(net, buff, sizeof(buff)) ||
              (stmt->param_count &&
               stmt->thd->protocol_simple.send_fields((List<Item> *)
                                                      &stmt->lex->param_list,
                                                      Protocol::SEND_EOF)));
}
#else
static bool send_prep_stmt(Prepared_statement *stmt,
                           uint columns __attribute__((unused)))
{
  THD *thd= stmt->thd;

  thd->client_stmt_id= stmt->id;
  thd->client_param_count= stmt->param_count;
  thd->clear_error();

  return 0;
}
#endif /*!EMBEDDED_LIBRARY*/


/*
  Read the length of the parameter data and return back to
  caller by positing the pointer to param data.
*/

#ifndef EMBEDDED_LIBRARY
static ulong get_param_length(uchar **packet, ulong len)
{
  reg1 uchar *pos= *packet;
  if (len < 1)
    return 0;
  if (*pos < 251)
  {
    (*packet)++;
    return (ulong) *pos;
  }
  if (len < 3)
    return 0;
  if (*pos == 252)
  {
    (*packet)+=3;
    return (ulong) uint2korr(pos+1);
  }
  if (len < 4)
    return 0;
  if (*pos == 253)
  {
    (*packet)+=4;
    return (ulong) uint3korr(pos+1);
  }
  if (len < 5)
    return 0;
  (*packet)+=9; // Must be 254 when here
  /*
    In our client-server protocol all numbers bigger than 2^24
    stored as 8 bytes with uint8korr. Here we always know that
    parameter length is less than 2^4 so don't look at the second
    4 bytes. But still we need to obey the protocol hence 9 in the
    assignment above.
  */
  return (ulong) uint4korr(pos+1);
}
#else
#define get_param_length(packet, len) len
#endif /*!EMBEDDED_LIBRARY*/

 /*
   Data conversion routines
   SYNOPSIS
   set_param_xx()
    param   parameter item
    pos     input data buffer
    len     length of data in the buffer

  All these functions read the data from pos, convert it to requested type
  and assign to param; pos is advanced to predefined length.

  Make a note that the NULL handling is examined at first execution
  (i.e. when input types altered) and for all subsequent executions
  we don't read any values for this.

  RETURN VALUE
    none
*/

static void set_param_tiny(Item_param *param, uchar **pos, ulong len)
{
#ifndef EMBEDDED_LIBRARY
  if (len < 1)
    return;
#endif
  int8 value= (int8) **pos;
  param->set_int(param->unsigned_flag ? (longlong) ((uint8) value) :
                                        (longlong) value, 4);
  *pos+= 1;
}

static void set_param_short(Item_param *param, uchar **pos, ulong len)
{
  int16 value;
#ifndef EMBEDDED_LIBRARY
  if (len < 2)
    return;
  value= sint2korr(*pos);
#else
  shortget(value, *pos);
#endif
  param->set_int(param->unsigned_flag ? (longlong) ((uint16) value) :
                                        (longlong) value, 6);
  *pos+= 2;
}

static void set_param_int32(Item_param *param, uchar **pos, ulong len)
{
  int32 value;
#ifndef EMBEDDED_LIBRARY
  if (len < 4)
    return;
  value= sint4korr(*pos);
#else
  longget(value, *pos);
#endif
  param->set_int(param->unsigned_flag ? (longlong) ((uint32) value) :
                                        (longlong) value, 11);
  *pos+= 4;
}

static void set_param_int64(Item_param *param, uchar **pos, ulong len)
{
  longlong value;
#ifndef EMBEDDED_LIBRARY
  if (len < 8)
    return;
  value= (longlong) sint8korr(*pos);
#else
  longlongget(value, *pos);
#endif
  param->set_int(value, 21);
  *pos+= 8;
}

static void set_param_float(Item_param *param, uchar **pos, ulong len)
{
#ifndef EMBEDDED_LIBRARY
  if (len < 4)
    return;
#endif
  float data;
  float4get(data,*pos);
  param->set_double((double) data);
  *pos+= 4;
}

static void set_param_double(Item_param *param, uchar **pos, ulong len)
{
#ifndef EMBEDDED_LIBRARY
  if (len < 8)
    return;
#endif
  double data;
  float8get(data,*pos);
  param->set_double((double) data);
  *pos+= 8;
}

static void set_param_decimal(Item_param *param, uchar **pos, ulong len)
{
  ulong length= get_param_length(pos, len);
  param->set_decimal((char*)*pos, length);
  *pos+= len;
}

#ifndef EMBEDDED_LIBRARY

/*
  Read date/time/datetime parameter values from network (binary
  protocol). See writing counterparts of these functions in
  libmysql.c (store_param_{time,date,datetime}).
*/

static void set_param_time(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME tm;
  ulong length= get_param_length(pos, len);

  if (length >= 8)
  {
    uchar *to= *pos;
    uint day;

    tm.neg= (bool) to[0];
    day= (uint) sint4korr(to+1);
    tm.hour=   (uint) to[5] + day * 24;
    tm.minute= (uint) to[6];
    tm.second= (uint) to[7];
    tm.second_part= (length > 8) ? (ulong) sint4korr(to+8) : 0;
    if (tm.hour > 838)
    {
      /* TODO: add warning 'Data truncated' here */
      tm.hour= 838;
      tm.minute= 59;
      tm.second= 59;
    }
    tm.day= tm.year= tm.month= 0;
  }
  else
    set_zero_time(&tm, MYSQL_TIMESTAMP_TIME);
  param->set_time(&tm, MYSQL_TIMESTAMP_TIME,
                  MAX_TIME_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);
  *pos+= length;
}

static void set_param_datetime(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME tm;
  ulong length= get_param_length(pos, len);

  if (length >= 4)
  {
    uchar *to= *pos;

    tm.neg=    0;
    tm.year=   (uint) sint2korr(to);
    tm.month=  (uint) to[2];
    tm.day=    (uint) to[3];
    if (length > 4)
    {
      tm.hour=   (uint) to[4];
      tm.minute= (uint) to[5];
      tm.second= (uint) to[6];
    }
    else
      tm.hour= tm.minute= tm.second= 0;

    tm.second_part= (length > 7) ? (ulong) sint4korr(to+7) : 0;
  }
  else
    set_zero_time(&tm, MYSQL_TIMESTAMP_DATETIME);
  param->set_time(&tm, MYSQL_TIMESTAMP_DATETIME,
                  MAX_DATETIME_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);
  *pos+= length;
}


static void set_param_date(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME tm;
  ulong length= get_param_length(pos, len);

  if (length >= 4)
  {
    uchar *to= *pos;

    tm.year=  (uint) sint2korr(to);
    tm.month=  (uint) to[2];
    tm.day= (uint) to[3];

    tm.hour= tm.minute= tm.second= 0;
    tm.second_part= 0;
    tm.neg= 0;
  }
  else
    set_zero_time(&tm, MYSQL_TIMESTAMP_DATE);
  param->set_time(&tm, MYSQL_TIMESTAMP_DATE,
                  MAX_DATE_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);
  *pos+= length;
}

#else/*!EMBEDDED_LIBRARY*/
void set_param_time(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME tm= *((MYSQL_TIME*)*pos);
  tm.hour+= tm.day * 24;
  tm.day= tm.year= tm.month= 0;
  if (tm.hour > 838)
  {
    /* TODO: add warning 'Data truncated' here */
    tm.hour= 838;
    tm.minute= 59;
    tm.second= 59;
  }
  param->set_time(&tm, MYSQL_TIMESTAMP_TIME,
                  MAX_TIME_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);

}

void set_param_datetime(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME *to= (MYSQL_TIME*)*pos;

  param->set_time(to, MYSQL_TIMESTAMP_DATETIME,
                  MAX_DATETIME_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);
}

void set_param_date(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME *to= (MYSQL_TIME*)*pos;

  param->set_time(to, MYSQL_TIMESTAMP_DATE,
                  MAX_DATE_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);
}
#endif /*!EMBEDDED_LIBRARY*/


static void set_param_str(Item_param *param, uchar **pos, ulong len)
{
  ulong length= get_param_length(pos, len);
  param->set_str((const char *)*pos, length);
  *pos+= length;
}


#undef get_param_length

static void setup_one_conversion_function(THD *thd, Item_param *param,
                                          uchar param_type)
{
  switch (param_type) {
  case MYSQL_TYPE_TINY:
    param->set_param_func= set_param_tiny;
    param->item_type= Item::INT_ITEM;
    param->item_result_type= INT_RESULT;
    break;
  case MYSQL_TYPE_SHORT:
    param->set_param_func= set_param_short;
    param->item_type= Item::INT_ITEM;
    param->item_result_type= INT_RESULT;
    break;
  case MYSQL_TYPE_LONG:
    param->set_param_func= set_param_int32;
    param->item_type= Item::INT_ITEM;
    param->item_result_type= INT_RESULT;
    break;
  case MYSQL_TYPE_LONGLONG:
    param->set_param_func= set_param_int64;
    param->item_type= Item::INT_ITEM;
    param->item_result_type= INT_RESULT;
    break;
  case MYSQL_TYPE_FLOAT:
    param->set_param_func= set_param_float;
    param->item_type= Item::REAL_ITEM;
    param->item_result_type= REAL_RESULT;
    break;
  case MYSQL_TYPE_DOUBLE:
    param->set_param_func= set_param_double;
    param->item_type= Item::REAL_ITEM;
    param->item_result_type= REAL_RESULT;
    break;
  case MYSQL_TYPE_DECIMAL:
  case MYSQL_TYPE_NEWDECIMAL:
    param->set_param_func= set_param_decimal;
    param->item_type= Item::DECIMAL_ITEM;
    param->item_result_type= DECIMAL_RESULT;
    break;
  case MYSQL_TYPE_TIME:
    param->set_param_func= set_param_time;
    param->item_type= Item::STRING_ITEM;
    param->item_result_type= STRING_RESULT;
    break;
  case MYSQL_TYPE_DATE:
    param->set_param_func= set_param_date;
    param->item_type= Item::STRING_ITEM;
    param->item_result_type= STRING_RESULT;
    break;
  case MYSQL_TYPE_DATETIME:
  case MYSQL_TYPE_TIMESTAMP:
    param->set_param_func= set_param_datetime;
    param->item_type= Item::STRING_ITEM;
    param->item_result_type= STRING_RESULT;
    break;
  case MYSQL_TYPE_TINY_BLOB:
  case MYSQL_TYPE_MEDIUM_BLOB:
  case MYSQL_TYPE_LONG_BLOB:
  case MYSQL_TYPE_BLOB:
    param->set_param_func= set_param_str;
    param->value.cs_info.character_set_client= &my_charset_bin;
    param->value.cs_info.final_character_set_of_str_value= &my_charset_bin;
    param->item_type= Item::STRING_ITEM;
    param->item_result_type= STRING_RESULT;
    break;
  default:
    /*
      The client library ensures that we won't get any other typecodes
      except typecodes above and typecodes for string types. Marking
      label as 'default' lets us to handle malformed packets as well.
    */
    {
      CHARSET_INFO *fromcs= thd->variables.character_set_client;
      CHARSET_INFO *tocs= thd->variables.collation_connection;
      uint32 dummy_offset;

      param->value.cs_info.character_set_client= fromcs;

      /*
        Setup source and destination character sets so that they
        are different only if conversion is necessary: this will
        make later checks easier.
      */
      param->value.cs_info.final_character_set_of_str_value=
        String::needs_conversion(0, fromcs, tocs, &dummy_offset) ?
        tocs : fromcs;
      param->set_param_func= set_param_str;
      /*
        Exact value of max_length is not known unless data is converted to
        charset of connection, so we have to set it later.
      */
      param->item_type= Item::STRING_ITEM;
      param->item_result_type= STRING_RESULT;
    }
  }
  param->param_type= (enum enum_field_types) param_type;
}

#ifndef EMBEDDED_LIBRARY
/*
  Update the parameter markers by reading data from client packet
  and if binary/update log is set, generate the valid query.
*/

static bool insert_params_withlog(Prepared_statement *stmt, uchar *null_array,
                                  uchar *read_pos, uchar *data_end,
                                  String *query)
{
  THD  *thd= stmt->thd;
  Item_param **begin= stmt->param_array;
  Item_param **end= begin + stmt->param_count;
  uint32 length= 0;

  String str;
  const String *res;

  DBUG_ENTER("insert_params_withlog");

  if (query->copy(stmt->query, stmt->query_length, default_charset_info))
    DBUG_RETURN(1);

  for (Item_param **it= begin; it < end; ++it)
  {
    Item_param *param= *it;
    if (param->state != Item_param::LONG_DATA_VALUE)
    {
      if (is_param_null(null_array, it - begin))
        param->set_null();
      else
      {
        if (read_pos >= data_end)
          DBUG_RETURN(1);
        param->set_param_func(param, &read_pos, data_end - read_pos);
      }
    }
    res= param->query_val_str(&str);
    if (param->convert_str_value(thd))
      DBUG_RETURN(1);                           /* out of memory */

    if (query->replace(param->pos_in_query+length, 1, *res))
      DBUG_RETURN(1);

    length+= res->length()-1;
  }
  DBUG_RETURN(0);
}


static bool insert_params(Prepared_statement *stmt, uchar *null_array,
                          uchar *read_pos, uchar *data_end,
                          String *expanded_query)
{
  Item_param **begin= stmt->param_array;
  Item_param **end= begin + stmt->param_count;

  DBUG_ENTER("insert_params");

  for (Item_param **it= begin; it < end; ++it)
  {
    Item_param *param= *it;
    if (param->state != Item_param::LONG_DATA_VALUE)
    {
      if (is_param_null(null_array, it - begin))
        param->set_null();
      else
      {
        if (read_pos >= data_end)
          DBUG_RETURN(1);
        param->set_param_func(param, &read_pos, data_end - read_pos);
      }
    }
    if (param->convert_str_value(stmt->thd))
      DBUG_RETURN(1);                           /* out of memory */
  }
  DBUG_RETURN(0);
}


static bool setup_conversion_functions(Prepared_statement *stmt,
                                       uchar **data, uchar *data_end)
{
  /* skip null bits */
  uchar *read_pos= *data + (stmt->param_count+7) / 8;

  DBUG_ENTER("setup_conversion_functions");

  if (*read_pos++) //types supplied / first execute
  {
    /*
      First execute or types altered by the client, setup the
      conversion routines for all parameters (one time)
    */
    Item_param **it= stmt->param_array;
    Item_param **end= it + stmt->param_count;
    THD *thd= stmt->thd;
    for (; it < end; ++it)
    {
      ushort typecode;
      const uint signed_bit= 1 << 15;

      if (read_pos >= data_end)
        DBUG_RETURN(1);

      typecode= sint2korr(read_pos);
      read_pos+= 2;
      (**it).unsigned_flag= test(typecode & signed_bit);
      setup_one_conversion_function(thd, *it, (uchar) (typecode & ~signed_bit));
    }
  }
  *data= read_pos;
  DBUG_RETURN(0);
}

#else

static bool emb_insert_params(Prepared_statement *stmt, String *expanded_query)
{
  THD *thd= stmt->thd;
  Item_param **it= stmt->param_array;
  Item_param **end= it + stmt->param_count;
  MYSQL_BIND *client_param= stmt->thd->client_params;

  DBUG_ENTER("emb_insert_params");

  for (; it < end; ++it, ++client_param)
  {
    Item_param *param= *it;
    setup_one_conversion_function(thd, param, client_param->buffer_type);
    if (param->state != Item_param::LONG_DATA_VALUE)
    {
      if (*client_param->is_null)
        param->set_null();
      else
      {
        uchar *buff= (uchar*) client_param->buffer;
        param->unsigned_flag= client_param->is_unsigned;
        param->set_param_func(param, &buff,
                              client_param->length ?
                              *client_param->length :
                              client_param->buffer_length);
      }
    }
    if (param->convert_str_value(thd))
      DBUG_RETURN(1);                           /* out of memory */
  }
  DBUG_RETURN(0);
}


static bool emb_insert_params_withlog(Prepared_statement *stmt, String *query)
{
  THD *thd= stmt->thd;
  Item_param **it= stmt->param_array;
  Item_param **end= it + stmt->param_count;
  MYSQL_BIND *client_param= thd->client_params;

  String str;
  const String *res;
  uint32 length= 0;

  DBUG_ENTER("emb_insert_params_withlog");

  if (query->copy(stmt->query, stmt->query_length, default_charset_info))
    DBUG_RETURN(1);

  for (; it < end; ++it, ++client_param)
  {
    Item_param *param= *it;
    setup_one_conversion_function(thd, param, client_param->buffer_type);
    if (param->state != Item_param::LONG_DATA_VALUE)
    {
      if (*client_param->is_null)
        param->set_null();
      else
      {
        uchar *buff= (uchar*)client_param->buffer;
        param->unsigned_flag= client_param->is_unsigned;
        param->set_param_func(param, &buff,
                              client_param->length ?
                              *client_param->length :
                              client_param->buffer_length);
      }
    }
    res= param->query_val_str(&str);
    if (param->convert_str_value(thd))
      DBUG_RETURN(1);                           /* out of memory */

    if (query->replace(param->pos_in_query+length, 1, *res))
      DBUG_RETURN(1);

    length+= res->length()-1;
  }
  DBUG_RETURN(0);
}

#endif /*!EMBEDDED_LIBRARY*/


/*
  Set prepared statement parameters from user variables.
  SYNOPSIS
    insert_params_from_vars()
      stmt      Statement
      varnames  List of variables. Caller must ensure that number of variables
                in the list is equal to number of statement parameters
      query     Ignored
*/

static bool insert_params_from_vars(Prepared_statement *stmt,
                                    List<LEX_STRING>& varnames,
                                    String *query __attribute__((unused)))
{
  Item_param **begin= stmt->param_array;
  Item_param **end= begin + stmt->param_count;
  user_var_entry *entry;
  LEX_STRING *varname;
  List_iterator<LEX_STRING> var_it(varnames);
  DBUG_ENTER("insert_params_from_vars");

  for (Item_param **it= begin; it < end; ++it)
  {
    Item_param *param= *it;
    varname= var_it++;
    entry= (user_var_entry*)hash_search(&stmt->thd->user_vars,
                                        (byte*) varname->str,
                                         varname->length);
    if (param->set_from_user_var(stmt->thd, entry) ||
        param->convert_str_value(stmt->thd))
      DBUG_RETURN(1);
  }
  DBUG_RETURN(0);
}


/*
  Do the same as insert_params_from_vars but also construct query text for
  binary log.
  SYNOPSIS
    insert_params_from_vars()
      stmt      Statement
      varnames  List of variables. Caller must ensure that number of variables
                in the list is equal to number of statement parameters
      query     The query with parameter markers replaced with their values
*/

static bool insert_params_from_vars_with_log(Prepared_statement *stmt,
                                             List<LEX_STRING>& varnames,
                                             String *query)
{
  Item_param **begin= stmt->param_array;
  Item_param **end= begin + stmt->param_count;
  user_var_entry *entry;
  LEX_STRING *varname;
  DBUG_ENTER("insert_params_from_vars");

  List_iterator<LEX_STRING> var_it(varnames);
  String buf;
  const String *val;
  uint32 length= 0;
  if (query->copy(stmt->query, stmt->query_length, default_charset_info))
    DBUG_RETURN(1);

  for (Item_param **it= begin; it < end; ++it)
  {
    Item_param *param= *it;
    varname= var_it++;
    if (get_var_with_binlog(stmt->thd, *varname, &entry))
        DBUG_RETURN(1);

    if (param->set_from_user_var(stmt->thd, entry))
      DBUG_RETURN(1);
    /* Insert @'escaped-varname' instead of parameter in the query */
    if (entry)
    {
      char *begin, *ptr;
      buf.length(0);
      if (buf.reserve(entry->name.length*2+3))
        DBUG_RETURN(1);

      begin= ptr= buf.c_ptr_quick();
      *ptr++= '@';
      *ptr++= '\'';
      ptr+= escape_string_for_mysql(&my_charset_utf8_general_ci,
                                    ptr, 0, entry->name.str,
                                    entry->name.length);
      *ptr++= '\'';
      buf.length(ptr - begin);
      val= &buf;
    }
    else
      val= &my_null_string;

    if (param->convert_str_value(stmt->thd))
      DBUG_RETURN(1);                           /* out of memory */

    if (query->replace(param->pos_in_query+length, 1, *val))
      DBUG_RETURN(1);
    length+= val->length()-1;
  }
  DBUG_RETURN(0);
}

/*
  Validate INSERT statement:

  SYNOPSIS
    mysql_test_insert()
    stmt        prepared statemen handler
    tables      global/local table list

  RETURN VALUE
    FALSE  success
    TRUE   error, error message is set in THD
*/

static bool mysql_test_insert(Prepared_statement *stmt,
                              TABLE_LIST *table_list,
                              List<Item> &fields,
                              List<List_item> &values_list,
                              List<Item> &update_fields,
                              List<Item> &update_values,
                              enum_duplicates duplic)
{
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;
  List_iterator_fast<List_item> its(values_list);
  List_item *values;
  DBUG_ENTER("mysql_test_insert");

  if (insert_precheck(thd, table_list))
    goto error;

  /*
    open temporary memory pool for temporary data allocated by derived
    tables & preparation procedure
    Note that this is done without locks (should not be needed as we will not
    access any data here)
    If we would use locks, then we have to ensure we are not using
    TL_WRITE_DELAYED as having two such locks can cause table corruption.
  */
  if (open_normal_and_derived_tables(thd, table_list, 0))
    goto error;

  if ((values= its++))
  {
    uint value_count;
    ulong counter= 0;
    Item *unused_conds= 0;

    if (table_list->table)
    {
      // don't allocate insert_values
      table_list->table->insert_values=(byte *)1;
    }

    if (mysql_prepare_insert(thd, table_list, table_list->table,
                             fields, values, update_fields, update_values,
                             duplic, &unused_conds, FALSE))
      goto error;

    value_count= values->elements;
    its.rewind();

    if (table_list->lock_type == TL_WRITE_DELAYED &&
        !(table_list->table->file->table_flags() & HA_CAN_INSERT_DELAYED))
    {
      my_error(ER_ILLEGAL_HA, MYF(0), (table_list->view ?
                                       table_list->view_name.str :
                                       table_list->table_name));
      goto error;
    }
    while ((values= its++))
    {
      counter++;
      if (values->elements != value_count)
      {
        my_error(ER_WRONG_VALUE_COUNT_ON_ROW, MYF(0), counter);
        goto error;
      }
      if (setup_fields(thd, 0, *values, 0, 0, 0))
        goto error;
    }
  }
  DBUG_RETURN(FALSE);

error:
  /* insert_values is cleared in open_table */
  DBUG_RETURN(TRUE);
}


/*
  Validate UPDATE statement

  SYNOPSIS
    mysql_test_update()
    stmt        prepared statemen handler
    tables      list of tables queries

  RETURN VALUE
    0   success
    1   error, error message is set in THD
    2   convert to multi_update
*/

static int mysql_test_update(Prepared_statement *stmt,
                              TABLE_LIST *table_list)
{
  int res;
  THD *thd= stmt->thd;
  uint table_count= 0;
  SELECT_LEX *select= &stmt->lex->select_lex;
#ifndef NO_EMBEDDED_ACCESS_CHECKS
  uint          want_privilege;
#endif
  DBUG_ENTER("mysql_test_update");

  if (update_precheck(thd, table_list))
    goto error;

  if (open_tables(thd, &table_list, &table_count, 0))
    goto error;

  if (table_list->multitable_view)
  {
    DBUG_ASSERT(table_list->view != 0);
    DBUG_PRINT("info", ("Switch to multi-update"));
    /* pass counter value */
    thd->lex->table_count= table_count;
    /* convert to multiupdate */
    DBUG_RETURN(2);
  }

  /*
    thd->fill_derived_tables() is false here for sure (because it is
    preparation of PS, so we even do not check it).
  */
  if (lock_tables(thd, table_list, table_count) ||
      mysql_handle_derived(thd->lex, &mysql_derived_prepare))
    goto error;

#ifndef NO_EMBEDDED_ACCESS_CHECKS
  /* TABLE_LIST contain right privilages request */
  want_privilege= table_list->grant.want_privilege;
#endif

  if (mysql_prepare_update(thd, table_list, &select->where,
                           select->order_list.elements,
                           (ORDER *) select->order_list.first))
    goto error;

#ifndef NO_EMBEDDED_ACCESS_CHECKS
  table_list->grant.want_privilege= want_privilege;
  table_list->table->grant.want_privilege= want_privilege;
#endif
  thd->lex->select_lex.no_wrap_view_item= TRUE;
  res= setup_fields(thd, 0, select->item_list, 1, 0, 0);
  thd->lex->select_lex.no_wrap_view_item= FALSE;
  if (res)
    goto error;
#ifndef NO_EMBEDDED_ACCESS_CHECKS
  /* Check values */
  table_list->grant.want_privilege=
  table_list->table->grant.want_privilege=
    (SELECT_ACL & ~table_list->table->grant.privilege);
#endif
  if (setup_fields(thd, 0, stmt->lex->value_list, 0, 0, 0))
    goto error;
  /* TODO: here we should send types of placeholders to the client. */
  DBUG_RETURN(0);
error:
  DBUG_RETURN(1);
}


/*
  Validate DELETE statement

  SYNOPSIS
    mysql_test_delete()
    stmt        prepared statemen handler
    tables      list of tables queries

  RETURN VALUE
    FALSE success
    TRUE  error, error message is set in THD
*/

static bool mysql_test_delete(Prepared_statement *stmt,
                              TABLE_LIST *table_list)
{
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;
  DBUG_ENTER("mysql_test_delete");

  if (delete_precheck(thd, table_list) ||
      open_and_lock_tables(thd, table_list))
    goto error;

  if (!table_list->table)
  {
    my_error(ER_VIEW_DELETE_MERGE_VIEW, MYF(0),
             table_list->view_db.str, table_list->view_name.str);
    goto error;
  }

  DBUG_RETURN(mysql_prepare_delete(thd, table_list, &lex->select_lex.where));
error:
  DBUG_RETURN(TRUE);
}


/*
  Validate SELECT statement.
  In case of success, if this query is not EXPLAIN, send column list info
  back to client.

  SYNOPSIS
    mysql_test_select()
    stmt        prepared statemen handler
    tables      list of tables queries

  RETURN VALUE
    FALSE success
    TRUE  error, sent to client
*/

static bool mysql_test_select(Prepared_statement *stmt,
                              TABLE_LIST *tables, bool text_protocol)
{
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;
  SELECT_LEX_UNIT *unit= &lex->unit;
  DBUG_ENTER("mysql_test_select");

  lex->select_lex.context.resolve_in_select_list= TRUE;

#ifndef NO_EMBEDDED_ACCESS_CHECKS
  ulong privilege= lex->exchange ? SELECT_ACL | FILE_ACL : SELECT_ACL;
  if (tables)
  {
    if (check_table_access(thd, privilege, tables,0))
      goto error;
  }
  else if (check_access(thd, privilege, any_db,0,0,0))
    goto error;
#endif

  if (!lex->result && !(lex->result= new (stmt->mem_root) select_send))
  {
    my_error(ER_OUTOFMEMORY, MYF(0), sizeof(select_send));
    goto error;
  }

  if (open_and_lock_tables(thd, tables))
    goto error;

  thd->used_tables= 0;                        // Updated by setup_fields

  /*
    JOIN::prepare calls
    It is not SELECT COMMAND for sure, so setup_tables will be called as
    usual, and we pass 0 as setup_tables_done_option
  */
  if (unit->prepare(thd, 0, 0, ""))
    goto error;
  if (!text_protocol)
  {
    if (lex->describe)
    {
      if (send_prep_stmt(stmt, 0) || thd->protocol->flush())
        goto error;
    }
    else
    {
      /* Make copy of item list, as change_columns may change it */
      List<Item> fields(lex->select_lex.item_list);

      /* Change columns if a procedure like analyse() */
      if (unit->last_procedure &&
          unit->last_procedure->change_columns(fields))
        goto error;

      /*
        We can use lex->result as it should've been
        prepared in unit->prepare call above.
      */
      if (send_prep_stmt(stmt, lex->result->field_count(fields)) ||
          lex->result->send_fields(fields, Protocol::SEND_EOF) ||
          thd->protocol->flush())
        goto error;
    }
  }
  DBUG_RETURN(FALSE);
error:
  DBUG_RETURN(TRUE);
}


/*
  Validate and prepare for execution DO statement expressions

  SYNOPSIS
    mysql_test_do_fields()
    stmt        prepared statemen handler
    tables      list of tables queries
    values      list of expressions

  RETURN VALUE
    FALSE success
    TRUE  error, error message is set in THD
*/

static bool mysql_test_do_fields(Prepared_statement *stmt,
                                TABLE_LIST *tables,
                                List<Item> *values)
{
  THD *thd= stmt->thd;

  DBUG_ENTER("mysql_test_do_fields");
  if (tables && check_table_access(thd, SELECT_ACL, tables, 0))
    DBUG_RETURN(TRUE);

  if (open_and_lock_tables(thd, tables))
    DBUG_RETURN(TRUE);
  DBUG_RETURN(setup_fields(thd, 0, *values, 0, 0, 0));
}


/*
  Validate and prepare for execution SET statement expressions

  SYNOPSIS
    mysql_test_set_fields()
    stmt        prepared statemen handler
    tables      list of tables queries
    values      list of expressions

  RETURN VALUE
    FALSE success
    TRUE  error
*/

static bool mysql_test_set_fields(Prepared_statement *stmt,
                                  TABLE_LIST *tables,
                                  List<set_var_base> *var_list)
{
  DBUG_ENTER("mysql_test_set_fields");
  List_iterator_fast<set_var_base> it(*var_list);
  THD *thd= stmt->thd;
  set_var_base *var;

  if (tables && check_table_access(thd, SELECT_ACL, tables, 0) ||
      open_and_lock_tables(thd, tables))
    goto error;

  while ((var= it++))
  {
    if (var->light_check(thd))
      goto error;
  }
  DBUG_RETURN(FALSE);
error:
  DBUG_RETURN(TRUE);
}


/*
  Check internal SELECT of the prepared command

  SYNOPSIS
    select_like_stmt_test()
      stmt                      - prepared statement handler
      specific_prepare          - function of command specific prepare
      setup_tables_done_option  - options to be passed to LEX::unit.prepare()

  NOTE
    This function won't directly open tables used in select. They should
    be opened either by calling function (and in this case you probably
    should use select_like_stmt_test_with_open_n_lock()) or by
    "specific_prepare" call (like this happens in case of multi-update).

  RETURN VALUE
    FALSE success
    TRUE  error, error message is set in THD
*/

static bool select_like_stmt_test(Prepared_statement *stmt,
                                  bool (*specific_prepare)(THD *thd),
                                  ulong setup_tables_done_option)
{
  DBUG_ENTER("select_like_stmt_test");
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;

  lex->select_lex.context.resolve_in_select_list= TRUE;

  if (specific_prepare && (*specific_prepare)(thd))
    DBUG_RETURN(TRUE);

  thd->used_tables= 0;                        // Updated by setup_fields

  /* Calls JOIN::prepare */
  DBUG_RETURN(lex->unit.prepare(thd, 0, setup_tables_done_option, ""));
}

/*
  Check internal SELECT of the prepared command (with opening and
  locking tables used).

  SYNOPSIS
    select_like_stmt_test_with_open_n_lock()
      stmt                      - prepared statement handler
      tables                    - list of tables to be opened and locked
                                  before calling specific_prepare function
      specific_prepare          - function of command specific prepare
      setup_tables_done_option  - options to be passed to LEX::unit.prepare()

  RETURN VALUE
    FALSE success
    TRUE  error
*/

static bool
select_like_stmt_test_with_open_n_lock(Prepared_statement *stmt,
                                       TABLE_LIST *tables,
                                       bool (*specific_prepare)(THD *thd),
                                       ulong setup_tables_done_option)
{
  DBUG_ENTER("select_like_stmt_test_with_open_n_lock");

  /*
    We should not call LEX::unit.cleanup() after this open_and_lock_tables()
    call because we don't allow prepared EXPLAIN yet so derived tables will
    clean up after themself.
  */
  if (open_and_lock_tables(stmt->thd, tables))
    DBUG_RETURN(TRUE);

  DBUG_RETURN(select_like_stmt_test(stmt, specific_prepare,
                                    setup_tables_done_option));
}


/*
  Validate and prepare for execution CREATE TABLE statement

  SYNOPSIS
    mysql_test_create_table()
    stmt        prepared statemen handler
    tables      list of tables queries

  RETURN VALUE
    FALSE   success
    TRUE    error, error message is set in THD
*/

static bool mysql_test_create_table(Prepared_statement *stmt)
{
  DBUG_ENTER("mysql_test_create_table");
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;
  SELECT_LEX *select_lex= &lex->select_lex;
  bool res= FALSE;
  /* Skip first table, which is the table we are creating */
  bool link_to_local;
  TABLE_LIST *create_table= lex->unlink_first_table(&link_to_local);
  TABLE_LIST *tables= lex->query_tables;

  if (create_table_precheck(thd, tables, create_table))
    DBUG_RETURN(TRUE);

  if (select_lex->item_list.elements)
  {
    select_lex->context.resolve_in_select_list= TRUE;
    res= select_like_stmt_test_with_open_n_lock(stmt, tables, 0, 0);
  }

  /* put tables back for PS rexecuting */
  lex->link_first_table_back(create_table, link_to_local);
  DBUG_RETURN(res);
}


/*
  Validate and prepare for execution multi update statement

  SYNOPSIS
    mysql_test_multiupdate()
    stmt        prepared statemen handler
    tables      list of tables queries
    converted   converted to multi-update from usual update

  RETURN VALUE
    FALSE success
    TRUE error
*/

static bool mysql_test_multiupdate(Prepared_statement *stmt,
                                  TABLE_LIST *tables,
                                  bool converted)
{
  /* if we switched from normal update, rights are checked */
  if (!converted && multi_update_precheck(stmt->thd, tables))
    return TRUE;

  return select_like_stmt_test(stmt, &mysql_multi_update_prepare,
                               OPTION_SETUP_TABLES_DONE);
}


/*
  Validate and prepare for execution multi delete statement

  SYNOPSIS
    mysql_test_multidelete()
    stmt        prepared statemen handler
    tables      list of tables queries

  RETURN VALUE
    0   success
    1   error, error message in THD is set.
*/

static bool mysql_test_multidelete(Prepared_statement *stmt,
                                  TABLE_LIST *tables)
{
  stmt->thd->lex->current_select= &stmt->thd->lex->select_lex;
  if (add_item_to_list(stmt->thd, new Item_null()))
  {
    my_error(ER_OUTOFMEMORY, MYF(0), 0);
    goto error;
  }

  if (multi_delete_precheck(stmt->thd, tables) ||
      select_like_stmt_test_with_open_n_lock(stmt, tables,
                                             &mysql_multi_delete_prepare,
                                             OPTION_SETUP_TABLES_DONE))
    goto error;
  if (!tables->table)
  {
    my_error(ER_VIEW_DELETE_MERGE_VIEW, MYF(0),
             tables->view_db.str, tables->view_name.str);
    goto error;
  }
  return FALSE;
error:
  return TRUE;
}


/*
  Wrapper for mysql_insert_select_prepare, to make change of local tables
  after open_and_lock_tables() call.

  SYNOPSIS
    mysql_insert_select_prepare_tester()
    thd     thread handler

  NOTE: we need remove first local tables after open_and_lock_tables,
  because mysql_handle_derived use local tables lists
*/

static bool mysql_insert_select_prepare_tester(THD *thd)
{
  TABLE_LIST *first;
  bool res;
  SELECT_LEX *first_select= &thd->lex->select_lex;
  /* Skip first table, which is the table we are inserting in */
  first_select->table_list.first= (byte*)(first=
                                          ((TABLE_LIST*)first_select->
                                           table_list.first)->next_local);
  res= mysql_insert_select_prepare(thd);
  /*
    insert/replace from SELECT give its SELECT_LEX for SELECT,
    and item_list belong to SELECT
  */
  thd->lex->select_lex.context.resolve_in_select_list= TRUE;
  thd->lex->select_lex.context.table_list= first;
  return res;
}


/*
  Validate and prepare for execution INSERT ... SELECT statement

  SYNOPSIS
    mysql_test_insert_select()
    stmt        prepared statemen handler
    tables      list of tables of query

  RETURN VALUE
    0   success
    1   error, sent to client
   -1   error, not sent to client
*/

static int mysql_test_insert_select(Prepared_statement *stmt,
                                    TABLE_LIST *tables)
{
  int res;
  LEX *lex= stmt->lex;
  TABLE_LIST *first_local_table;

  if (tables->table)
  {
    // don't allocate insert_values
    tables->table->insert_values=(byte *)1;
  }

  if (insert_precheck(stmt->thd, tables))
    return 1;

  /* store it, because mysql_insert_select_prepare_tester change it */
  first_local_table= (TABLE_LIST *)lex->select_lex.table_list.first;
  DBUG_ASSERT(first_local_table != 0);

  res=
    select_like_stmt_test_with_open_n_lock(stmt, tables,
                                           &mysql_insert_select_prepare_tester,
                                           OPTION_SETUP_TABLES_DONE);
  /* revert changes  made by mysql_insert_select_prepare_tester */
  lex->select_lex.table_list.first= (byte*) first_local_table;
  return res;
}


/*
  Perform semantic analysis of the parsed tree and send a response packet
  to the client.

  SYNOPSIS
    check_prepared_statement()
      stmt  prepared statement

  DESCRIPTION
    This function
    - opens all tables and checks access rights
    - validates semantics of statement columns and SQL functions
      by calling fix_fields.

  RETURN VALUE
    FALSE   success, statement metadata is sent to client
    TRUE   error, error message is set (but not sent)
*/

static bool check_prepared_statement(Prepared_statement *stmt,
                                     bool text_protocol)
{
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;
  SELECT_LEX *select_lex= &lex->select_lex;
  TABLE_LIST *tables;
  enum enum_sql_command sql_command= lex->sql_command;
  int res= 0;
  DBUG_ENTER("check_prepared_statement");
  DBUG_PRINT("enter",("command: %d, param_count: %ld",
                      sql_command, stmt->param_count));

  lex->first_lists_tables_same();
  tables= lex->query_tables;

  /* set context for commands which do not use setup_tables */
  lex->select_lex.context.resolve_in_table_list_only(select_lex->
                                                     get_table_list());

  switch (sql_command) {
  case SQLCOM_REPLACE:
  case SQLCOM_INSERT:
    res= mysql_test_insert(stmt, tables, lex->field_list,
                           lex->many_values,
                           select_lex->item_list, lex->value_list,
                           lex->duplicates);
    break;

  case SQLCOM_UPDATE:
    res= mysql_test_update(stmt, tables);
    /* mysql_test_update returns 2 if we need to switch to multi-update */
    if (res != 2)
      break;

  case SQLCOM_UPDATE_MULTI:
    res= mysql_test_multiupdate(stmt, tables, res == 2);
    break;

  case SQLCOM_DELETE:
    res= mysql_test_delete(stmt, tables);
    break;

  case SQLCOM_SELECT:
    if ((res= mysql_test_select(stmt, tables, text_protocol)))
      goto error;
    /* Statement and field info has already been sent */
    DBUG_RETURN(FALSE);

  case SQLCOM_CREATE_TABLE:
    res= mysql_test_create_table(stmt);
    break;

  case SQLCOM_DO:
    res= mysql_test_do_fields(stmt, tables, lex->insert_list);
    break;

  case SQLCOM_SET_OPTION:
    res= mysql_test_set_fields(stmt, tables, &lex->var_list);
    break;

  case SQLCOM_DELETE_MULTI:
    res= mysql_test_multidelete(stmt, tables);
    break;

  case SQLCOM_INSERT_SELECT:
  case SQLCOM_REPLACE_SELECT:
    res= mysql_test_insert_select(stmt, tables);
    break;

  case SQLCOM_SHOW_DATABASES:
  case SQLCOM_SHOW_PROCESSLIST:
  case SQLCOM_SHOW_STORAGE_ENGINES:
  case SQLCOM_SHOW_PRIVILEGES:
  case SQLCOM_SHOW_COLUMN_TYPES:
  case SQLCOM_SHOW_STATUS:
  case SQLCOM_SHOW_VARIABLES:
  case SQLCOM_SHOW_LOGS:
  case SQLCOM_SHOW_TABLES:
  case SQLCOM_SHOW_OPEN_TABLES:
  case SQLCOM_SHOW_CHARSETS:
  case SQLCOM_SHOW_COLLATIONS:
  case SQLCOM_SHOW_FIELDS:
  case SQLCOM_SHOW_KEYS:
  case SQLCOM_SHOW_CREATE_DB:
  case SQLCOM_SHOW_GRANTS:
  case SQLCOM_DROP_TABLE:
  case SQLCOM_RENAME_TABLE:
  case SQLCOM_ALTER_TABLE:
  case SQLCOM_COMMIT:
  case SQLCOM_CREATE_INDEX:
  case SQLCOM_DROP_INDEX:
  case SQLCOM_ROLLBACK:
  case SQLCOM_TRUNCATE:
  case SQLCOM_CALL:
    break;

  default:
    /* All other statements are not supported yet. */
    my_message(ER_UNSUPPORTED_PS, ER(ER_UNSUPPORTED_PS), MYF(0));
    goto error;
  }
  if (res == 0)
    DBUG_RETURN(text_protocol? FALSE : (send_prep_stmt(stmt, 0) ||
                                        thd->protocol->flush()));
error:
  DBUG_RETURN(TRUE);
}

/*
  Initialize array of parameters in statement from LEX.
  (We need to have quick access to items by number in mysql_stmt_get_longdata).
  This is to avoid using malloc/realloc in the parser.
*/

static bool init_param_array(Prepared_statement *stmt)
{
  LEX *lex= stmt->lex;
  if ((stmt->param_count= lex->param_list.elements))
  {
    if (stmt->param_count > (uint) UINT_MAX16)
    {
      /* Error code to be defined in 5.0 */
      my_message(ER_PS_MANY_PARAM, ER(ER_PS_MANY_PARAM), MYF(0));
      return TRUE;
    }
    Item_param **to;
    List_iterator<Item_param> param_iterator(lex->param_list);
    /* Use thd->mem_root as it points at statement mem_root */
    stmt->param_array= (Item_param **)
                       alloc_root(stmt->thd->mem_root,
                                  sizeof(Item_param*) * stmt->param_count);
    if (!stmt->param_array)
      return TRUE;
    for (to= stmt->param_array;
         to < stmt->param_array + stmt->param_count;
         ++to)
    {
      *to= param_iterator++;
    }
  }
  return FALSE;
}


/* Cleanup PS after execute/prepare and restore THD state */

static void cleanup_stmt_and_thd_after_use(Statement *stmt, THD *thd)
{
  stmt->lex->unit.cleanup();
  cleanup_items(stmt->free_list);
  thd->rollback_item_tree_changes();
  thd->cleanup_after_query();
}

/*
  Given a query string with parameter markers, create a Prepared Statement
  from it and send PS info back to the client.

  SYNOPSIS
    mysql_stmt_prepare()
      packet         query to be prepared
      packet_length  query string length, including ignored trailing NULL or
                     quote char.
      name           NULL or statement name. For unnamed statements binary PS
                     protocol is used, for named statements text protocol is
                     used.
  RETURN
    FALSE  OK, statement prepared successfully
    TRUE  Error

  NOTES
    This function parses the query and sends the total number of parameters
    and resultset metadata information back to client (if any), without
    executing the query i.e. without any log/disk writes. This allows the
    queries to be re-executed without re-parsing during execute.

    If parameter markers are found in the query, then store the information
    using Item_param along with maintaining a list in lex->param_array, so
    that a fast and direct retrieval can be made without going through all
    field items.

*/

bool mysql_stmt_prepare(THD *thd, char *packet, uint packet_length,
                        LEX_STRING *name)
{
  LEX *lex;
  Statement stmt_backup;
  Prepared_statement *stmt= new Prepared_statement(thd);
  bool error;
  DBUG_ENTER("mysql_stmt_prepare");

  DBUG_PRINT("prep_query", ("%s", packet));

  /*
    If this is an SQLCOM_PREPARE, we also increase Com_prepare_sql.
    However, it seems handy if com_stmt_prepare is increased always,
    no matter what kind of prepare is processed.
  */
  statistic_increment(thd->status_var.com_stmt_prepare, &LOCK_status);

  if (stmt == 0)
    DBUG_RETURN(TRUE);

  if (name)
  {
    stmt->name.length= name->length;
    if (!(stmt->name.str= memdup_root(stmt->mem_root, (char*)name->str,
                                      name->length)))
    {
      delete stmt;
      DBUG_RETURN(TRUE);
    }
  }

  if (thd->stmt_map.insert(stmt))
  {
    delete stmt;
    DBUG_RETURN(TRUE);
  }

  thd->set_n_backup_statement(stmt, &stmt_backup);
  thd->set_n_backup_item_arena(stmt, &stmt_backup);

  if (alloc_query(thd, packet, packet_length))
  {
    thd->restore_backup_statement(stmt, &stmt_backup);
    thd->restore_backup_item_arena(stmt, &stmt_backup);
    /* Statement map deletes statement on erase */
    thd->stmt_map.erase(stmt);
    DBUG_RETURN(TRUE);
  }

  mysql_log.write(thd, thd->command, "[%lu] %s", stmt->id, packet);

  thd->current_arena= stmt;
  mysql_init_query(thd, (uchar *) thd->query, thd->query_length);
  /* Reset warnings from previous command */
  mysql_reset_errors(thd, 0);
  lex= thd->lex;
  lex->safe_to_cache_query= 0;

  error= yyparse((void *)thd) || thd->is_fatal_error ||
         thd->net.report_error || init_param_array(stmt);
  /*
    While doing context analysis of the query (in check_prepared_statement)
    we allocate a lot of additional memory: for open tables, JOINs, derived
    tables, etc.  Let's save a snapshot of current parse tree to the
    statement and restore original THD. In cases when some tree
    transformation can be reused on execute, we set again thd->mem_root from
    stmt->mem_root (see setup_wild for one place where we do that).
  */
  thd->restore_backup_item_arena(stmt, &stmt_backup);

  if (!error)
    error= check_prepared_statement(stmt, test(name));

  /* restore to WAIT_PRIOR: QUERY_PRIOR is set inside alloc_query */
  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(),WAIT_PRIOR);
  if (error && thd->lex->sphead)
  {
    delete thd->lex->sphead;
    thd->lex->sphead= NULL;
  }
  lex_end(lex);
  close_thread_tables(thd);
  cleanup_stmt_and_thd_after_use(stmt, thd);
  thd->restore_backup_statement(stmt, &stmt_backup);
  thd->current_arena= thd;

  if (error)
  {
    /* Statement map deletes statement on erase */
    thd->stmt_map.erase(stmt);
    stmt= NULL;
  }
  else
  {
    stmt->setup_set_params();
    init_stmt_after_parse(thd, stmt->lex);
    stmt->state= Query_arena::PREPARED;
  }
  DBUG_RETURN(!stmt);
}


/*
  Init PS/SP specific parse tree members.
*/

void init_stmt_after_parse(THD *thd, LEX *lex)
{
  SELECT_LEX *sl= lex->all_selects_list;
  /*
    Switch off a temporary flag that prevents evaluation of
    subqueries in statement prepare.
  */
  for (; sl; sl= sl->next_select_in_list())
   sl->uncacheable&= ~UNCACHEABLE_PREPARE;
}


/* Reinit prepared statement/stored procedure before execution */

void reinit_stmt_before_use(THD *thd, LEX *lex)
{
  SELECT_LEX *sl= lex->all_selects_list;
  DBUG_ENTER("reinit_stmt_before_use");

  if (lex->empty_field_list_on_rset)
  {
    lex->empty_field_list_on_rset= 0;
    lex->field_list.empty();
  }
  for (; sl; sl= sl->next_select_in_list())
  {
    if (!sl->first_execution)
    {
      /* remove option which was put by mysql_explain_union() */
      sl->options&= ~SELECT_DESCRIBE;

      /* see unique_table() */
      sl->exclude_from_table_unique_test= FALSE;

      /*
        Copy WHERE clause pointers to avoid damaging they by optimisation
      */
      if (sl->prep_where)
      {
        sl->where= sl->prep_where->copy_andor_structure(thd);
        sl->where->cleanup();
      }
      DBUG_ASSERT(sl->join == 0);
      ORDER *order;
      /* Fix GROUP list */
      for (order= (ORDER *)sl->group_list.first; order; order= order->next)
        order->item= &order->item_ptr;
      /* Fix ORDER list */
      for (order= (ORDER *)sl->order_list.first; order; order= order->next)
        order->item= &order->item_ptr;
    }
    {
      SELECT_LEX_UNIT *unit= sl->master_unit();
      unit->unclean();
      unit->types.empty();
      /* for derived tables & PS (which can't be reset by Item_subquery) */
      unit->reinit_exec_mechanism();
    }
  }

  /*
    TODO: When the new table structure is ready, then have a status bit
    to indicate the table is altered, and re-do the setup_*
    and open the tables back.
  */
  /*
    NOTE: We should reset whole table list here including all tables added
    by prelocking algorithm (it is not a problem for substatements since
    they have their own table list).
  */
  for (TABLE_LIST *tables= lex->query_tables;
         tables;
         tables= tables->next_global)
  {
    /*
      Reset old pointers to TABLEs: they are not valid since the tables
      were closed in the end of previous prepare or execute call.
    */
    tables->table= 0;
    if (tables->nested_join)
      tables->nested_join->counter= 0;

    if (tables->prep_on_expr)
    {
      tables->on_expr= tables->prep_on_expr->copy_andor_structure(thd);
      tables->on_expr->cleanup();
    }
  }
  lex->current_select= &lex->select_lex;

  /* restore original list used in INSERT ... SELECT */
  if (lex->leaf_tables_insert)
    lex->select_lex.leaf_tables= lex->leaf_tables_insert;

  if (lex->result)
    lex->result->cleanup();

  DBUG_VOID_RETURN;
}


/*
  Clears parameters from data left from previous execution or long data

  SYNOPSIS
    reset_stmt_params()
    stmt        prepared statement for which parameters should be reset
*/

static void reset_stmt_params(Prepared_statement *stmt)
{
  Item_param **item= stmt->param_array;
  Item_param **end= item + stmt->param_count;
  for (;item < end ; ++item)
    (**item).reset();
}


/*
  Executes previously prepared query.
  If there is any parameters, then replace markers with the data supplied
  from client, and then execute the query.

  SYNOPSIS
    mysql_stmt_execute()
      thd            Current thread
      packet         Query string
      packet_length  Query string length, including terminator character.
*/

void mysql_stmt_execute(THD *thd, char *packet, uint packet_length)
{
  ulong stmt_id= uint4korr(packet);
  ulong flags= (ulong) ((uchar) packet[4]);
  Statement stmt_backup;
  Cursor *cursor;
  /*
    Query text for binary log, or empty string if the query is not put into
    binary log.
  */
  String expanded_query;
#ifndef EMBEDDED_LIBRARY
  uchar *packet_end= (uchar *) packet + packet_length - 1;
#endif
  Prepared_statement *stmt;
  DBUG_ENTER("mysql_stmt_execute");

  packet+= 9;                               /* stmt_id + 5 bytes of flags */

  statistic_increment(thd->status_var.com_stmt_execute, &LOCK_status);
  if (!(stmt= find_prepared_statement(thd, stmt_id, "mysql_stmt_execute")))
    DBUG_VOID_RETURN;

  DBUG_PRINT("exec_query:", ("%s", stmt->query));

  /* Check if we got an error when sending long data */
  if (stmt->state == Query_arena::ERROR)
  {
    my_message(stmt->last_errno, stmt->last_error, MYF(0));
    DBUG_VOID_RETURN;
  }

  cursor= stmt->cursor;
  if (cursor && cursor->is_open())
    stmt->close_cursor();

  DBUG_ASSERT(thd->free_list == NULL);
  mysql_reset_thd_for_next_command(thd);
  if (flags & (ulong) CURSOR_TYPE_READ_ONLY)
  {
    if (!stmt->lex->result || !stmt->lex->result->simple_select())
    {
      DBUG_PRINT("info",("Cursor asked for not SELECT stmt"));
      /*
        If lex->result is set in the parser, this is not a SELECT
        statement: we can't open a cursor for it.
      */
      flags= 0;
      my_error(ER_SP_BAD_CURSOR_QUERY, MYF(0));
      goto err;
    }
    else
    {
      DBUG_PRINT("info",("Using READ_ONLY cursor"));
      if (!cursor &&
          !(cursor= stmt->cursor= new (stmt->mem_root) Cursor(thd)))
        DBUG_VOID_RETURN;
      /* If lex->result is set, mysql_execute_command will use it */
      stmt->lex->result= &cursor->result;
    }
  }
#ifndef EMBEDDED_LIBRARY
  if (stmt->param_count)
  {
    uchar *null_array= (uchar *) packet;
    if (setup_conversion_functions(stmt, (uchar **) &packet, packet_end) ||
        stmt->set_params(stmt, null_array, (uchar *) packet, packet_end,
                         &expanded_query))
      goto set_params_data_err;
  }
#else
  /*
    In embedded library we re-install conversion routines each time
    we set params, and also we don't need to parse packet.
    So we do it in one function.
  */
  if (stmt->param_count && stmt->set_params_data(stmt, &expanded_query))
    goto set_params_data_err;
#endif
  thd->set_n_backup_statement(stmt, &stmt_backup);
  thd->current_arena= stmt;
  reinit_stmt_before_use(thd, stmt->lex);
  /* From now cursors assume that thd->mem_root is clean */
  if (expanded_query.length() &&
      alloc_query(thd, (char *)expanded_query.ptr(),
                  expanded_query.length()+1))
  {
    my_error(ER_OUTOFMEMORY, 0, expanded_query.length());
    goto err;
  }
  mysql_log.write(thd, thd->command, "[%lu] %s", stmt->id, thd->query);

  thd->protocol= &thd->protocol_prep;           // Switch to binary protocol
  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(),QUERY_PRIOR);
  mysql_execute_command(thd);
  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(), WAIT_PRIOR);
  thd->protocol= &thd->protocol_simple;         // Use normal protocol

  if (cursor && cursor->is_open())
  {
    /*
      It's safer if we grab THD state after mysql_execute_command is
      finished and not in Cursor::open(), because currently the call to
      Cursor::open is buried deep in JOIN::exec of the top level join.
    */
    cursor->init_from_thd(thd);
  }
  else
  {
    close_thread_tables(thd);
    cleanup_stmt_and_thd_after_use(stmt, thd);
    reset_stmt_params(stmt);
  }

  thd->set_statement(&stmt_backup);
  thd->current_arena= thd;
  DBUG_VOID_RETURN;

set_params_data_err:
  reset_stmt_params(stmt);
  my_error(ER_WRONG_ARGUMENTS, MYF(0), "mysql_stmt_execute");
err:
  DBUG_VOID_RETURN;
}


/*
  Execute prepared statement using parameter values from
  lex->prepared_stmt_params and send result to the client using text protocol.
*/

void mysql_sql_stmt_execute(THD *thd, LEX_STRING *stmt_name)
{
  Prepared_statement *stmt;
  /*
    Query text for binary log, or empty string if the query is not put into
    binary log.
  */
  String expanded_query;
  Statement stmt_backup;
  DBUG_ENTER("mysql_sql_stmt_execute");

  DBUG_ASSERT(thd->free_list == NULL);
  /* See comment for statistic_increment in mysql_stmt_prepare */
  statistic_increment(thd->status_var.com_stmt_execute, &LOCK_status);

  if (!(stmt= (Prepared_statement*)thd->stmt_map.find_by_name(stmt_name)))
  {
    my_error(ER_UNKNOWN_STMT_HANDLER, MYF(0), stmt_name->length,
             stmt_name->str, "EXECUTE");
    DBUG_VOID_RETURN;
  }

  if (stmt->param_count != thd->lex->prepared_stmt_params.elements)
  {
    my_error(ER_WRONG_ARGUMENTS, MYF(0), "EXECUTE");
    DBUG_VOID_RETURN;
  }

  /* Must go before setting variables, as it clears thd->user_var_events */
  mysql_reset_thd_for_next_command(thd);
  thd->set_n_backup_statement(stmt, &stmt_backup);
  if (stmt->set_params_from_vars(stmt,
                                 stmt_backup.lex->prepared_stmt_params,
                                 &expanded_query))
  {
    my_error(ER_WRONG_ARGUMENTS, MYF(0), "EXECUTE");
  }
  thd->command= COM_STMT_EXECUTE; /* For nice messages in general log */
  execute_stmt(thd, stmt, &expanded_query);
  thd->set_statement(&stmt_backup);
  DBUG_VOID_RETURN;
}


/*
  Execute prepared statement.
  SYNOPSIS
    execute_stmt()
      thd            Current thread
      stmt           Statement to execute
      expanded_query If binary log is enabled, query string with parameter
                     placeholders replaced with actual values. Otherwise empty
                     string.
  NOTES
    Caller must set parameter values and thd::protocol.
*/

static void execute_stmt(THD *thd, Prepared_statement *stmt,
                         String *expanded_query)
{
  DBUG_ENTER("execute_stmt");

  reinit_stmt_before_use(thd, stmt->lex);

  if (expanded_query->length() &&
      alloc_query(thd, (char *)expanded_query->ptr(),
                  expanded_query->length()+1))
  {
    my_error(ER_OUTOFMEMORY, MYF(0), expanded_query->length());
    DBUG_VOID_RETURN;
  }
  mysql_log.write(thd, thd->command, "[%lu] %s", stmt->id, thd->query);
  /*
    At first execution of prepared statement we will perform logical
    transformations of the query tree (i.e. negations elimination).
    This should be done permanently on the parse tree of this statement.
  */
  thd->current_arena= stmt;

  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(),QUERY_PRIOR);
  mysql_execute_command(thd);
  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(), WAIT_PRIOR);
  /*
    'start_time' is set in dispatch_command, but THD::query will
    be freed when we return from this function. So let's log the slow
    query here.
  */
  log_slow_statement(thd);
  /* Prevent from second logging in the end of dispatch_command */
  thd->enable_slow_log= FALSE;

  close_thread_tables(thd);                    // to close derived tables
  cleanup_stmt_and_thd_after_use(stmt, thd);
  reset_stmt_params(stmt);
  thd->current_arena= thd;

  if (stmt->state == Query_arena::PREPARED)
    stmt->state= Query_arena::EXECUTED;
  DBUG_VOID_RETURN;
}


/*
  COM_STMT_FETCH handler: fetches requested amount of rows from cursor

  SYNOPSIS
    mysql_stmt_fetch()
    thd                 Thread handler
    packet              Packet from client (with stmt_id & num_rows)
    packet_length       Length of packet
*/

void mysql_stmt_fetch(THD *thd, char *packet, uint packet_length)
{
  /* assume there is always place for 8-16 bytes */
  ulong stmt_id= uint4korr(packet);
  ulong num_rows= uint4korr(packet+4);
  Prepared_statement *stmt;
  Statement stmt_backup;
  Cursor *cursor;
  DBUG_ENTER("mysql_stmt_fetch");

  statistic_increment(thd->status_var.com_stmt_fetch, &LOCK_status);
  if (!(stmt= find_prepared_statement(thd, stmt_id, "mysql_stmt_fetch")))
    DBUG_VOID_RETURN;

  cursor= stmt->cursor;
  if (!cursor || !cursor->is_open())
  {
    my_error(ER_STMT_HAS_NO_OPEN_CURSOR, MYF(0), stmt_id);
    DBUG_VOID_RETURN;
  }

  thd->current_arena= stmt;
  thd->set_n_backup_statement(stmt, &stmt_backup);

  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(), QUERY_PRIOR);

  thd->protocol= &thd->protocol_prep;           // Switch to binary protocol
  cursor->fetch(num_rows);
  thd->protocol= &thd->protocol_simple;         // Use normal protocol

  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(), WAIT_PRIOR);

  if (!cursor->is_open())
  {
    /* We're done with the fetch: reset PS for next execution */
    cleanup_stmt_and_thd_after_use(stmt, thd);
    reset_stmt_params(stmt);
    /*
      Must be the last, as some momory is still needed for
      the previous calls.
    */
    free_root(cursor->mem_root, MYF(0));
  }

  thd->restore_backup_statement(stmt, &stmt_backup);
  thd->current_arena= thd;

  DBUG_VOID_RETURN;
}


/*
  Reset a prepared statement in case there was a recoverable error.
  SYNOPSIS
    mysql_stmt_reset()
      thd       Thread handle
      packet    Packet with stmt id

  DESCRIPTION
    This function resets statement to the state it was right after prepare.
    It can be used to:
     - clear an error happened during mysql_stmt_send_long_data
     - cancel long data stream for all placeholders without
       having to call mysql_stmt_execute.
    Sends 'OK' packet in case of success (statement was reset)
    or 'ERROR' packet (unrecoverable error/statement not found/etc).
*/

void mysql_stmt_reset(THD *thd, char *packet)
{
  /* There is always space for 4 bytes in buffer */
  ulong stmt_id= uint4korr(packet);
  Prepared_statement *stmt;
  Cursor *cursor;
  DBUG_ENTER("mysql_stmt_reset");

  statistic_increment(thd->status_var.com_stmt_reset, &LOCK_status);
  if (!(stmt= find_prepared_statement(thd, stmt_id, "mysql_stmt_reset")))
    DBUG_VOID_RETURN;

  stmt->close_cursor();                    /* will reset statement params */
  cursor= stmt->cursor;
  if (cursor && cursor->is_open())
  {
    thd->change_list= cursor->change_list;
    cursor->close(FALSE);
    cleanup_stmt_and_thd_after_use(stmt, thd);
    free_root(cursor->mem_root, MYF(0));
  }

  stmt->state= Query_arena::PREPARED;

  mysql_reset_thd_for_next_command(thd);
  send_ok(thd);

  DBUG_VOID_RETURN;
}


/*
  Delete a prepared statement from memory.
  Note: we don't send any reply to that command.
*/

void mysql_stmt_close(THD *thd, char *packet)
{
  /* There is always space for 4 bytes in packet buffer */
  ulong stmt_id= uint4korr(packet);
  Prepared_statement *stmt;

  DBUG_ENTER("mysql_stmt_close");

  statistic_increment(thd->status_var.com_stmt_close, &LOCK_status);
  if (!(stmt= find_prepared_statement(thd, stmt_id, "mysql_stmt_close")))
    DBUG_VOID_RETURN;

  /* Statement map deletes statement on erase */
  thd->stmt_map.erase(stmt);
  DBUG_VOID_RETURN;
}


/*
  Long data in pieces from client

  SYNOPSIS
    mysql_stmt_get_longdata()
    thd                 Thread handle
    pos                 String to append
    packet_length       Length of string

  DESCRIPTION
    Get a part of a long data.
    To make the protocol efficient, we are not sending any return packages
    here.
    If something goes wrong, then we will send the error on 'execute'

    We assume that the client takes care of checking that all parts are sent
    to the server. (No checking that we get a 'end of column' in the server)
*/

void mysql_stmt_get_longdata(THD *thd, char *packet, ulong packet_length)
{
  ulong stmt_id;
  uint param_number;
  Prepared_statement *stmt;
  Item_param *param;
  char *packet_end= packet + packet_length - 1;

  DBUG_ENTER("mysql_stmt_get_longdata");

  statistic_increment(thd->status_var.com_stmt_send_long_data, &LOCK_status);
#ifndef EMBEDDED_LIBRARY
  /* Minimal size of long data packet is 6 bytes */
  if ((ulong) (packet_end - packet) < MYSQL_LONG_DATA_HEADER)
  {
    my_error(ER_WRONG_ARGUMENTS, MYF(0), "mysql_stmt_send_long_data");
    DBUG_VOID_RETURN;
  }
#endif

  stmt_id= uint4korr(packet);
  packet+= 4;

  if (!(stmt=find_prepared_statement(thd, stmt_id,
                                     "mysql_stmt_send_long_data")))
    DBUG_VOID_RETURN;

  param_number= uint2korr(packet);
  packet+= 2;
#ifndef EMBEDDED_LIBRARY
  if (param_number >= stmt->param_count)
  {
    /* Error will be sent in execute call */
    stmt->state= Query_arena::ERROR;
    stmt->last_errno= ER_WRONG_ARGUMENTS;
    sprintf(stmt->last_error, ER(ER_WRONG_ARGUMENTS),
            "mysql_stmt_send_long_data");
    DBUG_VOID_RETURN;
  }
#endif

  param= stmt->param_array[param_number];

#ifndef EMBEDDED_LIBRARY
  if (param->set_longdata(packet, (ulong) (packet_end - packet)))
#else
  if (param->set_longdata(thd->extra_data, thd->extra_length))
#endif
  {
    stmt->state= Query_arena::ERROR;
    stmt->last_errno= ER_OUTOFMEMORY;
    sprintf(stmt->last_error, ER(ER_OUTOFMEMORY), 0);
  }
  DBUG_VOID_RETURN;
}


Prepared_statement::Prepared_statement(THD *thd_arg)
  :Statement(INITIALIZED, ++thd_arg->statement_id_counter,
             thd_arg->variables.query_alloc_block_size,
             thd_arg->variables.query_prealloc_size),
  thd(thd_arg),
  param_array(0),
  param_count(0),
  last_errno(0)
{
  *last_error= '\0';
}


void Prepared_statement::setup_set_params()
{
  /* Setup binary logging */
  if (mysql_bin_log.is_open() && is_update_query(lex->sql_command) ||
      mysql_log.is_open() || mysql_slow_log.is_open())
  {
    set_params_from_vars= insert_params_from_vars_with_log;
#ifndef EMBEDDED_LIBRARY
    set_params= insert_params_withlog;
#else
    set_params_data= emb_insert_params_withlog;
#endif
  }
  else
  {
    set_params_from_vars= insert_params_from_vars;
#ifndef EMBEDDED_LIBRARY
    set_params= insert_params;
#else
    set_params_data= emb_insert_params;
#endif
  }
}


Prepared_statement::~Prepared_statement()
{
  if (cursor)
  {
    if (cursor->is_open())
    {
      cursor->close(FALSE);
      free_items();
      free_root(cursor->mem_root, MYF(0));
    }
    cursor->Cursor::~Cursor();
  }
  else
    free_items();
  delete lex->result;
}


Query_arena::Type Prepared_statement::type() const
{
  return PREPARED_STATEMENT;
}


void Prepared_statement::close_cursor()
{
  if (cursor && cursor->is_open())
  {
    thd->change_list= cursor->change_list;
    cursor->close(FALSE);
    cleanup_stmt_and_thd_after_use(this, thd);
    free_root(cursor->mem_root, MYF(0));
  }
  /*
    Clear parameters from data which could be set by
    mysql_stmt_send_long_data() call.
  */
  reset_stmt_params(this);
}