handler.h

#ifndef HANDLER_INCLUDED
#define HANDLER_INCLUDED

/*
   Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; version 2 of
   the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
*/

/* Definitions for parameters to do with handler-routines */

#include "my_pthread.h"
#include <algorithm>
#include "sql_const.h"
#include "mysqld.h"                             /* server_id */
#include "sql_plugin.h"        /* plugin_ref, st_plugin_int, plugin */
#include "thr_lock.h"          /* thr_lock_type, THR_LOCK_DATA */
#include "sql_cache.h"
#include "structs.h"                            /* SHOW_COMP_OPTION */

#include <my_global.h>
#include <my_compare.h>
#include <ft_global.h>
#include <keycache.h>

class Alter_info;

// the following is for checking tables

#define HA_ADMIN_ALREADY_DONE     1
#define HA_ADMIN_OK               0
#define HA_ADMIN_NOT_IMPLEMENTED -1
#define HA_ADMIN_FAILED          -2
#define HA_ADMIN_CORRUPT         -3
#define HA_ADMIN_INTERNAL_ERROR  -4
#define HA_ADMIN_INVALID         -5
#define HA_ADMIN_REJECT          -6
#define HA_ADMIN_TRY_ALTER       -7
#define HA_ADMIN_WRONG_CHECKSUM  -8
#define HA_ADMIN_NOT_BASE_TABLE  -9
#define HA_ADMIN_NEEDS_UPGRADE  -10
#define HA_ADMIN_NEEDS_ALTER    -11
#define HA_ADMIN_NEEDS_CHECK    -12

enum enum_alter_inplace_result {
  HA_ALTER_ERROR,
  HA_ALTER_INPLACE_NOT_SUPPORTED,
  HA_ALTER_INPLACE_EXCLUSIVE_LOCK,
  HA_ALTER_INPLACE_SHARED_LOCK_AFTER_PREPARE,
  HA_ALTER_INPLACE_SHARED_LOCK,
  HA_ALTER_INPLACE_NO_LOCK_AFTER_PREPARE,
  HA_ALTER_INPLACE_NO_LOCK
};

/* Bits in table_flags() to show what database can do */

#define HA_NO_TRANSACTIONS     (1 << 0) /* Doesn't support transactions */
#define HA_PARTIAL_COLUMN_READ (1 << 1) /* read may not return all columns */
#define HA_TABLE_SCAN_ON_INDEX (1 << 2) /* No separate data/index file */
/*
  The following should be set if the following is not true when scanning
  a table with rnd_next()
  - We will see all rows (including deleted ones)
  - Row positions are 'table->s->db_record_offset' apart
  If this flag is not set, filesort will do a position() call for each matched
  row to be able to find the row later.
*/
#define HA_REC_NOT_IN_SEQ      (1 << 3)
#define HA_CAN_GEOMETRY        (1 << 4)
/*
  Reading keys in random order is as fast as reading keys in sort order
  (Used in records.cc to decide if we should use a record cache and by
  filesort to decide if we should sort key + data or key + pointer-to-row
*/
#define HA_FAST_KEY_READ       (1 << 5)
/*
  Set the following flag if we on delete should force all key to be read
  and on update read all keys that changes
*/
#define HA_REQUIRES_KEY_COLUMNS_FOR_DELETE (1 << 6)
#define HA_NULL_IN_KEY         (1 << 7) /* One can have keys with NULL */
#define HA_DUPLICATE_POS       (1 << 8)    /* position() gives dup row */
#define HA_NO_BLOBS            (1 << 9) /* Doesn't support blobs */
#define HA_CAN_INDEX_BLOBS     (1 << 10)
#define HA_AUTO_PART_KEY       (1 << 11) /* auto-increment in multi-part key */
#define HA_REQUIRE_PRIMARY_KEY (1 << 12) /* .. and can't create a hidden one */
#define HA_STATS_RECORDS_IS_EXACT (1 << 13) /* stats.records is exact */
/*
  INSERT_DELAYED only works with handlers that uses MySQL internal table
  level locks
*/
#define HA_CAN_INSERT_DELAYED  (1 << 14)
/*
  If we get the primary key columns for free when we do an index read
  (usually, it also implies that HA_PRIMARY_KEY_REQUIRED_FOR_POSITION
  flag is set).
*/
#define HA_PRIMARY_KEY_IN_READ_INDEX (1 << 15)
/*
  If HA_PRIMARY_KEY_REQUIRED_FOR_POSITION is set, it means that to position()
  uses a primary key given by the record argument.
  Without primary key, we can't call position().
  If not set, the position is returned as the current rows position
  regardless of what argument is given.
*/ 
#define HA_PRIMARY_KEY_REQUIRED_FOR_POSITION (1 << 16) 
#define HA_CAN_RTREEKEYS       (1 << 17)
#define HA_NOT_DELETE_WITH_CACHE (1 << 18)
/*
  The following is we need to a primary key to delete (and update) a row.
  If there is no primary key, all columns needs to be read on update and delete
*/
#define HA_PRIMARY_KEY_REQUIRED_FOR_DELETE (1 << 19)
#define HA_NO_PREFIX_CHAR_KEYS (1 << 20)
#define HA_CAN_FULLTEXT        (1 << 21)
#define HA_CAN_SQL_HANDLER     (1 << 22)
#define HA_NO_AUTO_INCREMENT   (1 << 23)
#define HA_HAS_CHECKSUM        (1 << 24)
/* Table data are stored in separate files (for lower_case_table_names) */
#define HA_FILE_BASED          (1 << 26)
#define HA_NO_VARCHAR          (1 << 27)
#define HA_CAN_BIT_FIELD       (1 << 28) /* supports bit fields */
#define HA_ANY_INDEX_MAY_BE_UNIQUE (1 << 30)
#define HA_NO_COPY_ON_ALTER    (LL(1) << 31)
#define HA_HAS_RECORDS         (LL(1) << 32) /* records() gives exact count*/
/* Has it's own method of binlog logging */
#define HA_HAS_OWN_BINLOGGING  (LL(1) << 33)
/*
  Engine is capable of row-format and statement-format logging,
  respectively
*/
#define HA_BINLOG_ROW_CAPABLE  (LL(1) << 34)
#define HA_BINLOG_STMT_CAPABLE (LL(1) << 35)
/*
    When a multiple key conflict happens in a REPLACE command mysql
    expects the conflicts to be reported in the ascending order of
    key names.

    For e.g.

    CREATE TABLE t1 (a INT, UNIQUE (a), b INT NOT NULL, UNIQUE (b), c INT NOT
                     NULL, INDEX(c));

    REPLACE INTO t1 VALUES (1,1,1),(2,2,2),(2,1,3);

    MySQL expects the conflict with 'a' to be reported before the conflict with
    'b'.

    If the underlying storage engine does not report the conflicting keys in
    ascending order, it causes unexpected errors when the REPLACE command is
    executed.

    This flag helps the underlying SE to inform the server that the keys are not
    ordered.
*/
#define HA_DUPLICATE_KEY_NOT_IN_ORDER    (LL(1) << 36)
/*
  Engine supports REPAIR TABLE. Used by CHECK TABLE FOR UPGRADE if an
  incompatible table is detected. If this flag is set, CHECK TABLE FOR UPGRADE
  will report ER_TABLE_NEEDS_UPGRADE, otherwise ER_TABLE_NEED_REBUILD.
*/
#define HA_CAN_REPAIR                    (LL(1) << 37)

/*
  Set of all binlog flags. Currently only contain the capabilities
  flags.
 */
#define HA_BINLOG_FLAGS (HA_BINLOG_ROW_CAPABLE | HA_BINLOG_STMT_CAPABLE)

#define HA_READ_BEFORE_WRITE_REMOVAL  (LL(1) << 38)

/*
  Engine supports extended fulltext API
 */
#define HA_CAN_FULLTEXT_EXT              (LL(1) << 39)

/*
  Storage engine doesn't synchronize result set with expected table contents.
  Used by replication slave to check if it is possible to retrieve rows from
  the table when deciding whether to do a full table scan, index scan or hash
  scan while applying a row event.
 */
#define HA_READ_OUT_OF_SYNC              (LL(1) << 40)

/*
  Storage engine supports table export using the
  FLUSH TABLE <table_list> FOR EXPORT statement.
 */
#define HA_CAN_EXPORT                 (LL(1) << 41)

/*
  The handler don't want accesses to this table to 
  be const-table optimized
*/
#define HA_BLOCK_CONST_TABLE          (LL(1) << 42)

/* bits in index_flags(index_number) for what you can do with index */
#define HA_READ_NEXT            1       /* TODO really use this flag */
#define HA_READ_PREV            2       /* supports ::index_prev */
#define HA_READ_ORDER           4       /* index_next/prev follow sort order */
#define HA_READ_RANGE           8       /* can find all records in a range */
#define HA_ONLY_WHOLE_INDEX     16      /* Can't use part key searches */
#define HA_KEYREAD_ONLY         64      /* Support HA_EXTRA_KEYREAD */
/*
  Index scan will not return records in rowid order. Not guaranteed to be
  set for unordered (e.g. HASH) indexes.
*/
#define HA_KEY_SCAN_NOT_ROR     128 
#define HA_DO_INDEX_COND_PUSHDOWN  256 /* Supports Index Condition Pushdown */



#define HA_PARTITION_FUNCTION_SUPPORTED         (1L << 0)
#define HA_FAST_CHANGE_PARTITION                (1L << 1)
#define HA_PARTITION_ONE_PHASE                  (1L << 2)

/* operations for disable/enable indexes */
#define HA_KEY_SWITCH_NONUNIQ      0
#define HA_KEY_SWITCH_ALL          1
#define HA_KEY_SWITCH_NONUNIQ_SAVE 2
#define HA_KEY_SWITCH_ALL_SAVE     3

/*
  Note: the following includes binlog and closing 0.
  so: innodb + bdb + ndb + binlog + myisam + myisammrg + archive +
      example + csv + heap + blackhole + federated + 0
  (yes, the sum is deliberately inaccurate)
  TODO remove the limit, use dynarrays
*/
#define MAX_HA 15

/*
  Use this instead of 0 as the initial value for the slot number of
  handlerton, so that we can distinguish uninitialized slot number
  from slot 0.
*/
#define HA_SLOT_UNDEF ((uint)-1)

/*
  Parameters for open() (in register form->filestat)
  HA_GET_INFO does an implicit HA_ABORT_IF_LOCKED
*/

#define HA_OPEN_KEYFILE         1
#define HA_OPEN_RNDFILE         2
#define HA_GET_INDEX            4
#define HA_GET_INFO             8       /* do a ha_info() after open */
#define HA_READ_ONLY            16      /* File opened as readonly */
/* Try readonly if can't open with read and write */
#define HA_TRY_READ_ONLY        32
#define HA_WAIT_IF_LOCKED       64      /* Wait if locked on open */
#define HA_ABORT_IF_LOCKED      128     /* skip if locked on open.*/
#define HA_BLOCK_LOCK           256     /* unlock when reading some records */
#define HA_OPEN_TEMPORARY       512

        /* Some key definitions */
#define HA_KEY_NULL_LENGTH      1
#define HA_KEY_BLOB_LENGTH      2

#define HA_LEX_CREATE_TMP_TABLE 1
#define HA_LEX_CREATE_IF_NOT_EXISTS 2
#define HA_LEX_CREATE_TABLE_LIKE 4
#define HA_OPTION_NO_CHECKSUM   (1L << 17)
#define HA_OPTION_NO_DELAY_KEY_WRITE (1L << 18)
#define HA_MAX_REC_LENGTH       65535U

/* Table caching type */
#define HA_CACHE_TBL_NONTRANSACT 0
#define HA_CACHE_TBL_NOCACHE     1
#define HA_CACHE_TBL_ASKTRANSACT 2
#define HA_CACHE_TBL_TRANSACT    4

// WITH CONSISTENT SNAPSHOT option
static const uint MYSQL_START_TRANS_OPT_WITH_CONS_SNAPSHOT = 1;
// READ ONLY option
static const uint MYSQL_START_TRANS_OPT_READ_ONLY          = 2;
// READ WRITE option
static const uint MYSQL_START_TRANS_OPT_READ_WRITE         = 4;

/* Flags for method is_fatal_error */
#define HA_CHECK_DUP_KEY 1
#define HA_CHECK_DUP_UNIQUE 2
#define HA_CHECK_DUP (HA_CHECK_DUP_KEY + HA_CHECK_DUP_UNIQUE)

enum legacy_db_type
{
  DB_TYPE_UNKNOWN=0,DB_TYPE_DIAB_ISAM=1,
  DB_TYPE_HASH,DB_TYPE_MISAM,DB_TYPE_PISAM,
  DB_TYPE_RMS_ISAM, DB_TYPE_HEAP, DB_TYPE_ISAM,
  DB_TYPE_MRG_ISAM, DB_TYPE_MYISAM, DB_TYPE_MRG_MYISAM,
  DB_TYPE_BERKELEY_DB, DB_TYPE_INNODB,
  DB_TYPE_GEMINI, DB_TYPE_NDBCLUSTER,
  DB_TYPE_EXAMPLE_DB, DB_TYPE_ARCHIVE_DB, DB_TYPE_CSV_DB,
  DB_TYPE_FEDERATED_DB,
  DB_TYPE_BLACKHOLE_DB,
  DB_TYPE_PARTITION_DB,
  DB_TYPE_BINLOG,
  DB_TYPE_SOLID,
  DB_TYPE_PBXT,
  DB_TYPE_TABLE_FUNCTION,
  DB_TYPE_MEMCACHE,
  DB_TYPE_FALCON,
  DB_TYPE_MARIA,
  DB_TYPE_PERFORMANCE_SCHEMA,
  DB_TYPE_FIRST_DYNAMIC=42,
  DB_TYPE_DEFAULT=127 // Must be last
};

enum row_type { ROW_TYPE_NOT_USED=-1, ROW_TYPE_DEFAULT, ROW_TYPE_FIXED,
                ROW_TYPE_DYNAMIC, ROW_TYPE_COMPRESSED,
                ROW_TYPE_REDUNDANT, ROW_TYPE_COMPACT,
                ROW_TYPE_PAGE };

/* Specifies data storage format for individual columns */
enum column_format_type {
  COLUMN_FORMAT_TYPE_DEFAULT=   0, /* Not specified (use engine default) */
  COLUMN_FORMAT_TYPE_FIXED=     1, /* FIXED format */
  COLUMN_FORMAT_TYPE_DYNAMIC=   2  /* DYNAMIC format */
};

enum enum_binlog_func {
  BFN_RESET_LOGS=        1,
  BFN_RESET_SLAVE=       2,
  BFN_BINLOG_WAIT=       3,
  BFN_BINLOG_END=        4,
  BFN_BINLOG_PURGE_FILE= 5
};

enum enum_binlog_command {
  LOGCOM_CREATE_TABLE,
  LOGCOM_ALTER_TABLE,
  LOGCOM_RENAME_TABLE,
  LOGCOM_DROP_TABLE,
  LOGCOM_CREATE_DB,
  LOGCOM_ALTER_DB,
  LOGCOM_DROP_DB
};

/* struct to hold information about the table that should be created */

/* Bits in used_fields */
#define HA_CREATE_USED_AUTO             (1L << 0)
#define HA_CREATE_USED_RAID             (1L << 1) //RAID is no longer availble
#define HA_CREATE_USED_UNION            (1L << 2)
#define HA_CREATE_USED_INSERT_METHOD    (1L << 3)
#define HA_CREATE_USED_MIN_ROWS         (1L << 4)
#define HA_CREATE_USED_MAX_ROWS         (1L << 5)
#define HA_CREATE_USED_AVG_ROW_LENGTH   (1L << 6)
#define HA_CREATE_USED_PACK_KEYS        (1L << 7)
#define HA_CREATE_USED_CHARSET          (1L << 8)
#define HA_CREATE_USED_DEFAULT_CHARSET  (1L << 9)
#define HA_CREATE_USED_DATADIR          (1L << 10)
#define HA_CREATE_USED_INDEXDIR         (1L << 11)
#define HA_CREATE_USED_ENGINE           (1L << 12)
#define HA_CREATE_USED_CHECKSUM         (1L << 13)
#define HA_CREATE_USED_DELAY_KEY_WRITE  (1L << 14)
#define HA_CREATE_USED_ROW_FORMAT       (1L << 15)
#define HA_CREATE_USED_COMMENT          (1L << 16)
#define HA_CREATE_USED_PASSWORD         (1L << 17)
#define HA_CREATE_USED_CONNECTION       (1L << 18)
#define HA_CREATE_USED_KEY_BLOCK_SIZE   (1L << 19)

#define HA_CREATE_USED_TRANSACTIONAL    (1L << 20)

#define HA_CREATE_USED_PAGE_CHECKSUM    (1L << 21)

#define HA_CREATE_USED_STATS_PERSISTENT (1L << 22)

#define HA_CREATE_USED_STATS_AUTO_RECALC (1L << 23)

#define HA_CREATE_USED_STATS_SAMPLE_PAGES (1L << 24)


/*
  This is master database for most of system tables. However there
  can be other databases which can hold system tables. Respective
  storage engines define their own system database names.
*/
extern const char *mysqld_system_database;

/*
  Structure to hold list of system_database.system_table.
  This is used at both mysqld and storage engine layer.
*/
struct st_system_tablename
{
  const char *db;
  const char *tablename;
};


typedef ulonglong my_xid; // this line is the same as in log_event.h
#define MYSQL_XID_PREFIX "MySQLXid"
#define MYSQL_XID_PREFIX_LEN 8 // must be a multiple of 8
#define MYSQL_XID_OFFSET (MYSQL_XID_PREFIX_LEN+sizeof(server_id))
#define MYSQL_XID_GTRID_LEN (MYSQL_XID_OFFSET+sizeof(my_xid))

#define XIDDATASIZE MYSQL_XIDDATASIZE
#define MAXGTRIDSIZE 64
#define MAXBQUALSIZE 64

#define COMPATIBLE_DATA_YES 0
#define COMPATIBLE_DATA_NO  1

namespace AQP {
  class Join_plan;
};

struct xid_t {
  long formatID;
  long gtrid_length;
  long bqual_length;
  char data[XIDDATASIZE];  // not \0-terminated !

  xid_t() {}                                /* Remove gcc warning */  
  bool eq(struct xid_t *xid)
  { return eq(xid->gtrid_length, xid->bqual_length, xid->data); }
  bool eq(long g, long b, const char *d)
  { return g == gtrid_length && b == bqual_length && !memcmp(d, data, g+b); }
  void set(struct xid_t *xid)
  { memcpy(this, xid, xid->length()); }
  void set(long f, const char *g, long gl, const char *b, long bl)
  {
    formatID= f;
    memcpy(data, g, gtrid_length= gl);
    memcpy(data+gl, b, bqual_length= bl);
  }
  void set(ulonglong xid)
  {
    my_xid tmp;
    formatID= 1;
    set(MYSQL_XID_PREFIX_LEN, 0, MYSQL_XID_PREFIX);
    memcpy(data+MYSQL_XID_PREFIX_LEN, &server_id, sizeof(server_id));
    tmp= xid;
    memcpy(data+MYSQL_XID_OFFSET, &tmp, sizeof(tmp));
    gtrid_length=MYSQL_XID_GTRID_LEN;
  }
  void set(long g, long b, const char *d)
  {
    formatID= 1;
    gtrid_length= g;
    bqual_length= b;
    memcpy(data, d, g+b);
  }
  bool is_null() { return formatID == -1; }
  void null() { formatID= -1; }
  my_xid quick_get_my_xid()
  {
    my_xid tmp;
    memcpy(&tmp, data+MYSQL_XID_OFFSET, sizeof(tmp));
    return tmp;
  }
  my_xid get_my_xid()
  {
    return gtrid_length == MYSQL_XID_GTRID_LEN && bqual_length == 0 &&
           !memcmp(data, MYSQL_XID_PREFIX, MYSQL_XID_PREFIX_LEN) ?
           quick_get_my_xid() : 0;
  }
  uint length()
  {
    return sizeof(formatID)+sizeof(gtrid_length)+sizeof(bqual_length)+
           gtrid_length+bqual_length;
  }
  uchar *key()
  {
    return (uchar *)&gtrid_length;
  }
  uint key_length()
  {
    return sizeof(gtrid_length)+sizeof(bqual_length)+gtrid_length+bqual_length;
  }
};
typedef struct xid_t XID;

/* for recover() handlerton call */
#define MIN_XID_LIST_SIZE  128
#define MAX_XID_LIST_SIZE  (1024*128)

/*
  These structures are used to pass information from a set of SQL commands
  on add/drop/change tablespace definitions to the proper hton.
*/
#define UNDEF_NODEGROUP 65535
enum ts_command_type
{
  TS_CMD_NOT_DEFINED = -1,
  CREATE_TABLESPACE = 0,
  ALTER_TABLESPACE = 1,
  CREATE_LOGFILE_GROUP = 2,
  ALTER_LOGFILE_GROUP = 3,
  DROP_TABLESPACE = 4,
  DROP_LOGFILE_GROUP = 5,
  CHANGE_FILE_TABLESPACE = 6,
  ALTER_ACCESS_MODE_TABLESPACE = 7
};

enum ts_alter_tablespace_type
{
  TS_ALTER_TABLESPACE_TYPE_NOT_DEFINED = -1,
  ALTER_TABLESPACE_ADD_FILE = 1,
  ALTER_TABLESPACE_DROP_FILE = 2
};

enum tablespace_access_mode
{
  TS_NOT_DEFINED= -1,
  TS_READ_ONLY = 0,
  TS_READ_WRITE = 1,
  TS_NOT_ACCESSIBLE = 2
};

struct handlerton;
class st_alter_tablespace : public Sql_alloc
{
  public:
  const char *tablespace_name;
  const char *logfile_group_name;
  enum ts_command_type ts_cmd_type;
  enum ts_alter_tablespace_type ts_alter_tablespace_type;
  const char *data_file_name;
  const char *undo_file_name;
  const char *redo_file_name;
  ulonglong extent_size;
  ulonglong undo_buffer_size;
  ulonglong redo_buffer_size;
  ulonglong initial_size;
  ulonglong autoextend_size;
  ulonglong max_size;
  uint nodegroup_id;
  handlerton *storage_engine;
  bool wait_until_completed;
  const char *ts_comment;
  enum tablespace_access_mode ts_access_mode;
  st_alter_tablespace()
  {
    tablespace_name= NULL;
    logfile_group_name= "DEFAULT_LG"; //Default log file group
    ts_cmd_type= TS_CMD_NOT_DEFINED;
    data_file_name= NULL;
    undo_file_name= NULL;
    redo_file_name= NULL;
    extent_size= 1024*1024;        //Default 1 MByte
    undo_buffer_size= 8*1024*1024; //Default 8 MByte
    redo_buffer_size= 8*1024*1024; //Default 8 MByte
    initial_size= 128*1024*1024;   //Default 128 MByte
    autoextend_size= 0;            //No autoextension as default
    max_size= 0;                   //Max size == initial size => no extension
    storage_engine= NULL;
    nodegroup_id= UNDEF_NODEGROUP;
    wait_until_completed= TRUE;
    ts_comment= NULL;
    ts_access_mode= TS_NOT_DEFINED;
  }
};

/* The handler for a table type.  Will be included in the TABLE structure */

struct TABLE;

/*
  Make sure that the order of schema_tables and enum_schema_tables are the same.
*/
enum enum_schema_tables
{
  SCH_CHARSETS= 0,
  SCH_COLLATIONS,
  SCH_COLLATION_CHARACTER_SET_APPLICABILITY,
  SCH_COLUMNS,
  SCH_COLUMN_PRIVILEGES,
  SCH_ENGINES,
  SCH_EVENTS,
  SCH_FILES,
  SCH_GLOBAL_STATUS,
  SCH_GLOBAL_VARIABLES,
  SCH_KEY_COLUMN_USAGE,
  SCH_OPEN_TABLES,
  SCH_OPTIMIZER_TRACE,
  SCH_PARAMETERS,
  SCH_PARTITIONS,
  SCH_PLUGINS,
  SCH_PROCESSLIST,
  SCH_PROFILES,
  SCH_REFERENTIAL_CONSTRAINTS,
  SCH_PROCEDURES,
  SCH_SCHEMATA,
  SCH_SCHEMA_PRIVILEGES,
  SCH_SESSION_STATUS,
  SCH_SESSION_VARIABLES,
  SCH_STATISTICS,
  SCH_STATUS,
  SCH_TABLES,
  SCH_TABLESPACES,
  SCH_TABLE_CONSTRAINTS,
  SCH_TABLE_NAMES,
  SCH_TABLE_PRIVILEGES,
  SCH_TRIGGERS,
  SCH_USER_PRIVILEGES,
  SCH_VARIABLES,
  SCH_VIEWS
};

struct TABLE_SHARE;
struct st_foreign_key_info;
typedef struct st_foreign_key_info FOREIGN_KEY_INFO;
typedef bool (stat_print_fn)(THD *thd, const char *type, uint type_len,
                             const char *file, uint file_len,
                             const char *status, uint status_len);
enum ha_stat_type { HA_ENGINE_STATUS, HA_ENGINE_LOGS, HA_ENGINE_MUTEX };
extern st_plugin_int *hton2plugin[MAX_HA];

/* Transaction log maintains type definitions */
enum log_status
{
  HA_LOG_STATUS_FREE= 0,      /* log is free and can be deleted */
  HA_LOG_STATUS_INUSE= 1,     /* log can't be deleted because it is in use */
  HA_LOG_STATUS_NOSUCHLOG= 2  /* no such log (can't be returned by
                                the log iterator status) */
};
/*
  Function for signaling that the log file changed its state from
  LOG_STATUS_INUSE to LOG_STATUS_FREE

  Now it do nothing, will be implemented as part of new transaction
  log management for engines.
  TODO: implement the function.
*/
void signal_log_not_needed(struct handlerton, char *log_file);
/*
  Data of transaction log iterator.
*/
struct handler_log_file_data {
  LEX_STRING filename;
  enum log_status status;
};


enum handler_iterator_type
{
  /* request of transaction log iterator */
  HA_TRANSACTLOG_ITERATOR= 1
};
enum handler_create_iterator_result
{
  HA_ITERATOR_OK,          /* iterator created */
  HA_ITERATOR_UNSUPPORTED, /* such type of iterator is not supported */
  HA_ITERATOR_ERROR        /* error during iterator creation */
};

/*
  Iterator structure. Can be used by handler/handlerton for different purposes.

  Iterator should be created in the way to point "before" the first object
  it iterate, so next() call move it to the first object or return !=0 if
  there is nothing to iterate through.
*/
struct handler_iterator {
  /*
    Moves iterator to next record and return 0 or return !=0
    if there is no records.
    iterator_object will be filled by this function if next() returns 0.
    Content of the iterator_object depend on iterator type.
  */
  int (*next)(struct handler_iterator *, void *iterator_object);
  /*
    Free resources allocated by iterator, after this call iterator
    is not usable.
  */
  void (*destroy)(struct handler_iterator *);
  /*
    Pointer to buffer for the iterator to use.
    Should be allocated by function which created the iterator and
    destroied by freed by above "destroy" call
  */
  void *buffer;
};

class handler;
/*
  handlerton is a singleton structure - one instance per storage engine -
  to provide access to storage engine functionality that works on the
  "global" level (unlike handler class that works on a per-table basis)

  usually handlerton instance is defined statically in ha_xxx.cc as

  static handlerton { ... } xxx_hton;

  savepoint_*, prepare, recover, and *_by_xid pointers can be 0.
*/
struct handlerton
{
  /*
    Historical marker for if the engine is available of not
  */
  SHOW_COMP_OPTION state;

  /*
    Historical number used for frm file to determine the correct storage engine.
    This is going away and new engines will just use "name" for this.
  */
  enum legacy_db_type db_type;
  /*
    each storage engine has it's own memory area (actually a pointer)
    in the thd, for storing per-connection information.
    It is accessed as

      thd->ha_data[xxx_hton.slot]

   slot number is initialized by MySQL after xxx_init() is called.
   */
   uint slot;
   /*
     to store per-savepoint data storage engine is provided with an area
     of a requested size (0 is ok here).
     savepoint_offset must be initialized statically to the size of
     the needed memory to store per-savepoint information.
     After xxx_init it is changed to be an offset to savepoint storage
     area and need not be used by storage engine.
     see binlog_hton and binlog_savepoint_set/rollback for an example.
   */
   uint savepoint_offset;
   /*
     handlerton methods:

     close_connection is only called if
     thd->ha_data[xxx_hton.slot] is non-zero, so even if you don't need
     this storage area - set it to something, so that MySQL would know
     this storage engine was accessed in this connection
   */
   int  (*close_connection)(handlerton *hton, THD *thd);
   /*
     sv points to an uninitialized storage area of requested size
     (see savepoint_offset description)
   */
   int  (*savepoint_set)(handlerton *hton, THD *thd, void *sv);
   /*
     sv points to a storage area, that was earlier passed
     to the savepoint_set call
   */
   int  (*savepoint_rollback)(handlerton *hton, THD *thd, void *sv);
   int  (*savepoint_release)(handlerton *hton, THD *thd, void *sv);
   /*
     'all' is true if it's a real commit, that makes persistent changes
     'all' is false if it's not in fact a commit but an end of the
     statement that is part of the transaction.
     NOTE 'all' is also false in auto-commit mode where 'end of statement'
     and 'real commit' mean the same event.
   */
   int  (*commit)(handlerton *hton, THD *thd, bool all);
   int  (*rollback)(handlerton *hton, THD *thd, bool all);
   int  (*prepare)(handlerton *hton, THD *thd, bool all);
   int  (*recover)(handlerton *hton, XID *xid_list, uint len);
   int  (*commit_by_xid)(handlerton *hton, XID *xid);
   int  (*rollback_by_xid)(handlerton *hton, XID *xid);
   void *(*create_cursor_read_view)(handlerton *hton, THD *thd);
   void (*set_cursor_read_view)(handlerton *hton, THD *thd, void *read_view);
   void (*close_cursor_read_view)(handlerton *hton, THD *thd, void *read_view);
   handler *(*create)(handlerton *hton, TABLE_SHARE *table, MEM_ROOT *mem_root);
   void (*drop_database)(handlerton *hton, char* path);
   int (*panic)(handlerton *hton, enum ha_panic_function flag);
   int (*start_consistent_snapshot)(handlerton *hton, THD *thd);
   bool (*flush_logs)(handlerton *hton);
   bool (*show_status)(handlerton *hton, THD *thd, stat_print_fn *print, enum ha_stat_type stat);
   uint (*partition_flags)();
   uint (*alter_table_flags)(uint flags);
   int (*alter_tablespace)(handlerton *hton, THD *thd, st_alter_tablespace *ts_info);
   int (*fill_is_table)(handlerton *hton, THD *thd, TABLE_LIST *tables, 
                        class Item *cond, 
                        enum enum_schema_tables);
   uint32 flags;                                /* global handler flags */
   /*
      Those handlerton functions below are properly initialized at handler
      init.
   */
   int (*binlog_func)(handlerton *hton, THD *thd, enum_binlog_func fn, void *arg);
   void (*binlog_log_query)(handlerton *hton, THD *thd, 
                            enum_binlog_command binlog_command,
                            const char *query, uint query_length,
                            const char *db, const char *table_name);
   int (*release_temporary_latches)(handlerton *hton, THD *thd);

   /*
     Get log status.
     If log_status is null then the handler do not support transaction
     log information (i.e. log iterator can't be created).
     (see example of implementation in handler.cc, TRANS_LOG_MGM_EXAMPLE_CODE)

   */
   enum log_status (*get_log_status)(handlerton *hton, char *log);

   /*
     Iterators creator.
     Presence of the pointer should be checked before using
   */
   enum handler_create_iterator_result
     (*create_iterator)(handlerton *hton, enum handler_iterator_type type,
                        struct handler_iterator *fill_this_in);
   int (*discover)(handlerton *hton, THD* thd, const char *db, 
                   const char *name,
                   uchar **frmblob, 
                   size_t *frmlen);
   int (*find_files)(handlerton *hton, THD *thd,
                     const char *db,
                     const char *path,
                     const char *wild, bool dir, List<LEX_STRING> *files);
   int (*table_exists_in_engine)(handlerton *hton, THD* thd, const char *db,
                                 const char *name);
   int (*make_pushed_join)(handlerton *hton, THD* thd, 
                           const AQP::Join_plan* plan);

  const char* (*system_database)();

  bool (*is_supported_system_table)(const char *db,
                                    const char *table_name,
                                    bool is_sql_layer_system_table);

   uint32 license; /* Flag for Engine License */
   void *data; /* Location for engines to keep personal structures */
};


/* Possible flags of a handlerton (there can be 32 of them) */
#define HTON_NO_FLAGS                 0
#define HTON_CLOSE_CURSORS_AT_COMMIT (1 << 0)
#define HTON_ALTER_NOT_SUPPORTED     (1 << 1) //Engine does not support alter
#define HTON_CAN_RECREATE            (1 << 2) //Delete all is used fro truncate
#define HTON_HIDDEN                  (1 << 3) //Engine does not appear in lists
#define HTON_FLUSH_AFTER_RENAME      (1 << 4)
#define HTON_NOT_USER_SELECTABLE     (1 << 5)
#define HTON_TEMPORARY_NOT_SUPPORTED (1 << 6) //Having temporary tables not supported
#define HTON_SUPPORT_LOG_TABLES      (1 << 7) //Engine supports log tables
#define HTON_NO_PARTITION            (1 << 8) //You can not partition these tables

/*
  This flag should be set when deciding that the engine does not allow row based
  binary logging (RBL) optimizations.

  Currently, setting this flag, means that table's read/write_set will be left 
  untouched when logging changes to tables in this engine. In practice this 
  means that the server will not mess around with table->write_set and/or 
  table->read_set when using RBL and deciding whether to log full or minimal rows.

  It's valuable for instance for virtual tables, eg: Performance Schema which have
  no meaning for replication.
*/
#define HTON_NO_BINLOG_ROW_OPT       (1 << 9)

#define HTON_SUPPORTS_EXTENDED_KEYS  (1 << 10)


enum enum_tx_isolation { ISO_READ_UNCOMMITTED, ISO_READ_COMMITTED,
                         ISO_REPEATABLE_READ, ISO_SERIALIZABLE};


typedef struct {
  ulonglong data_file_length;
  ulonglong max_data_file_length;
  ulonglong index_file_length;
  ulonglong delete_length;
  ha_rows records;
  ulong mean_rec_length;
  ulong create_time;
  ulong check_time;
  ulong update_time;
  ulonglong check_sum;
} PARTITION_STATS;

#define UNDEF_NODEGROUP 65535
class Item;
struct st_table_log_memory_entry;

class partition_info;

struct st_partition_iter;

enum enum_ha_unused { HA_CHOICE_UNDEF, HA_CHOICE_NO, HA_CHOICE_YES };

enum enum_stats_auto_recalc { HA_STATS_AUTO_RECALC_DEFAULT= 0,
                              HA_STATS_AUTO_RECALC_ON,
                              HA_STATS_AUTO_RECALC_OFF };

typedef struct st_ha_create_information
{
  const CHARSET_INFO *table_charset, *default_table_charset;
  LEX_STRING connect_string;
  const char *password, *tablespace;
  LEX_STRING comment;
  const char *data_file_name, *index_file_name;
  const char *alias;
  ulonglong max_rows,min_rows;
  ulonglong auto_increment_value;
  ulong table_options;
  ulong avg_row_length;
  ulong used_fields;
  ulong key_block_size;
  uint stats_sample_pages;              /* number of pages to sample during
                                        stats estimation, if used, otherwise 0. */
  enum_stats_auto_recalc stats_auto_recalc;
  SQL_I_List<TABLE_LIST> merge_list;
  handlerton *db_type;
  enum row_type row_type;
  uint null_bits;                       /* NULL bits at start of record */
  uint options;                         /* OR of HA_CREATE_ options */
  uint merge_insert_method;
  uint extra_size;                      /* length of extra data segment */
  bool varchar;                         /* 1 if table has a VARCHAR */
  enum ha_storage_media storage_media;  /* DEFAULT, DISK or MEMORY */
} HA_CREATE_INFO;

class inplace_alter_handler_ctx : public Sql_alloc
{
public:
  inplace_alter_handler_ctx() {}

  virtual ~inplace_alter_handler_ctx() {}
};


class Alter_inplace_info
{
public:
  typedef ulong HA_ALTER_FLAGS;

  // Add non-unique, non-primary index
  static const HA_ALTER_FLAGS ADD_INDEX                  = 1L << 0;

  // Drop non-unique, non-primary index
  static const HA_ALTER_FLAGS DROP_INDEX                 = 1L << 1;

  // Add unique, non-primary index
  static const HA_ALTER_FLAGS ADD_UNIQUE_INDEX           = 1L << 2;

  // Drop unique, non-primary index
  static const HA_ALTER_FLAGS DROP_UNIQUE_INDEX          = 1L << 3;

  // Add primary index
  static const HA_ALTER_FLAGS ADD_PK_INDEX               = 1L << 4;

  // Drop primary index
  static const HA_ALTER_FLAGS DROP_PK_INDEX              = 1L << 5;

  // Add column
  static const HA_ALTER_FLAGS ADD_COLUMN                 = 1L << 6;

  // Drop column
  static const HA_ALTER_FLAGS DROP_COLUMN                = 1L << 7;

  // Rename column
  static const HA_ALTER_FLAGS ALTER_COLUMN_NAME          = 1L << 8;

  // Change column datatype
  static const HA_ALTER_FLAGS ALTER_COLUMN_TYPE          = 1L << 9;

  static const HA_ALTER_FLAGS ALTER_COLUMN_EQUAL_PACK_LENGTH = 1L << 10;

  // Reorder column
  static const HA_ALTER_FLAGS ALTER_COLUMN_ORDER         = 1L << 11;

  // Change column from NOT NULL to NULL
  static const HA_ALTER_FLAGS ALTER_COLUMN_NULLABLE      = 1L << 12;

  // Change column from NULL to NOT NULL
  static const HA_ALTER_FLAGS ALTER_COLUMN_NOT_NULLABLE  = 1L << 13;

  // Set or remove default column value
  static const HA_ALTER_FLAGS ALTER_COLUMN_DEFAULT       = 1L << 14;

  // Add foreign key
  static const HA_ALTER_FLAGS ADD_FOREIGN_KEY            = 1L << 15;

  // Drop foreign key
  static const HA_ALTER_FLAGS DROP_FOREIGN_KEY           = 1L << 16;

  // table_options changed, see HA_CREATE_INFO::used_fields for details.
  static const HA_ALTER_FLAGS CHANGE_CREATE_OPTION       = 1L << 17;

  // Table is renamed
  static const HA_ALTER_FLAGS ALTER_RENAME               = 1L << 18;

  // Change the storage type of column 
  static const HA_ALTER_FLAGS ALTER_COLUMN_STORAGE_TYPE = 1L << 19;

  // Change the column format of column
  static const HA_ALTER_FLAGS ALTER_COLUMN_COLUMN_FORMAT = 1L << 20;

  // Add partition
  static const HA_ALTER_FLAGS ADD_PARTITION              = 1L << 21;

  // Drop partition
  static const HA_ALTER_FLAGS DROP_PARTITION             = 1L << 22;

  // Changing partition options
  static const HA_ALTER_FLAGS ALTER_PARTITION            = 1L << 23;

  // Coalesce partition
  static const HA_ALTER_FLAGS COALESCE_PARTITION         = 1L << 24;

  // Reorganize partition ... into
  static const HA_ALTER_FLAGS REORGANIZE_PARTITION       = 1L << 25;

  // Reorganize partition
  static const HA_ALTER_FLAGS ALTER_TABLE_REORG          = 1L << 26;

  // Remove partitioning
  static const HA_ALTER_FLAGS ALTER_REMOVE_PARTITIONING  = 1L << 27;

  // Partition operation with ALL keyword
  static const HA_ALTER_FLAGS ALTER_ALL_PARTITION        = 1L << 28;

  HA_CREATE_INFO *create_info;

  Alter_info *alter_info;

  KEY  *key_info_buffer;

  uint key_count;

  uint index_drop_count;

  KEY  **index_drop_buffer;

  uint index_add_count;

  uint *index_add_buffer;

  inplace_alter_handler_ctx *handler_ctx;

  inplace_alter_handler_ctx **group_commit_ctx;

  HA_ALTER_FLAGS handler_flags;

  partition_info *modified_part_info;

  const bool ignore;

  bool online;

  const char *unsupported_reason;

  Alter_inplace_info(HA_CREATE_INFO *create_info_arg,
                     Alter_info *alter_info_arg,
                     KEY *key_info_arg, uint key_count_arg,
                     partition_info *modified_part_info_arg,
                     bool ignore_arg)
    : create_info(create_info_arg),
    alter_info(alter_info_arg),
    key_info_buffer(key_info_arg),
    key_count(key_count_arg),
    index_drop_count(0),
    index_drop_buffer(NULL),
    index_add_count(0),
    index_add_buffer(NULL),
    handler_ctx(NULL),
    group_commit_ctx(NULL),
    handler_flags(0),
    modified_part_info(modified_part_info_arg),
    ignore(ignore_arg),
    online(false),
    unsupported_reason(NULL)
  {}

  ~Alter_inplace_info()
  {
    delete handler_ctx;
  }

  void report_unsupported_error(const char *not_supported,
                                const char *try_instead);
};


typedef struct st_key_create_information
{
  enum ha_key_alg algorithm;
  ulong block_size;
  LEX_STRING parser_name;
  LEX_STRING comment;
  bool check_for_duplicate_indexes;
} KEY_CREATE_INFO;


/*
  Class for maintaining hooks used inside operations on tables such
  as: create table functions, delete table functions, and alter table
  functions.

  Class is using the Template Method pattern to separate the public
  usage interface from the private inheritance interface.  This
  imposes no overhead, since the public non-virtual function is small
  enough to be inlined.

  The hooks are usually used for functions that does several things,
  e.g., create_table_from_items(), which both create a table and lock
  it.
 */
class TABLEOP_HOOKS
{
public:
  TABLEOP_HOOKS() {}
  virtual ~TABLEOP_HOOKS() {}

  inline void prelock(TABLE **tables, uint count)
  {
    do_prelock(tables, count);
  }

  inline int postlock(TABLE **tables, uint count)
  {
    return do_postlock(tables, count);
  }
private:
  /* Function primitive that is called prior to locking tables */
  virtual void do_prelock(TABLE **tables, uint count)
  {
    /* Default is to do nothing */
  }

  virtual int do_postlock(TABLE **tables, uint count)
  {
    return 0;                           /* Default is to do nothing */
  }
};

typedef struct st_savepoint SAVEPOINT;
extern ulong savepoint_alloc_size;
extern KEY_CREATE_INFO default_key_create_info;

typedef struct st_ha_check_opt
{
  st_ha_check_opt() {}                        /* Remove gcc warning */
  uint flags;       /* isam layer flags (e.g. for myisamchk) */
  uint sql_flags;   /* sql layer flags - for something myisamchk cannot do */
  KEY_CACHE *key_cache; /* new key cache when changing key cache */
  void init();
} HA_CHECK_OPT;



/*
  This is a buffer area that the handler can use to store rows.
  'end_of_used_area' should be kept updated after calls to
  read-functions so that other parts of the code can use the
  remaining area (until next read calls is issued).
*/

typedef struct st_handler_buffer
{
  uchar *buffer;         /* Buffer one can start using */
  uchar *buffer_end;     /* End of buffer */
  uchar *end_of_used_area;     /* End of area that was used by handler */
} HANDLER_BUFFER;

typedef struct system_status_var SSV;


typedef void *range_seq_t;

typedef struct st_range_seq_if
{
  /*
    Initialize the traversal of range sequence
    
    SYNOPSIS
      init()
        init_params  The seq_init_param parameter 
        n_ranges     The number of ranges obtained 
        flags        A combination of HA_MRR_SINGLE_POINT, HA_MRR_FIXED_KEY

    RETURN
      An opaque value to be used as RANGE_SEQ_IF::next() parameter
  */
  range_seq_t (*init)(void *init_params, uint n_ranges, uint flags);


  /*
    Get the next range in the range sequence

    SYNOPSIS
      next()
        seq    The value returned by RANGE_SEQ_IF::init()
        range  OUT Information about the next range
    
    RETURN
      0 - Ok, the range structure filled with info about the next range
      1 - No more ranges
  */
  uint (*next) (range_seq_t seq, KEY_MULTI_RANGE *range);

  /*
    Check whether range_info orders to skip the next record

    SYNOPSIS
      skip_record()
        seq         The value returned by RANGE_SEQ_IF::init()
        range_info  Information about the next range 
                    (Ignored if MRR_NO_ASSOCIATION is set)
        rowid       Rowid of the record to be checked (ignored if set to 0)
    
    RETURN
      1 - Record with this range_info and/or this rowid shall be filtered
          out from the stream of records returned by multi_range_read_next()
      0 - The record shall be left in the stream
  */ 
  bool (*skip_record) (range_seq_t seq, char *range_info, uchar *rowid);

  /*
    Check if the record combination matches the index condition
    SYNOPSIS
      skip_index_tuple()
        seq         The value returned by RANGE_SEQ_IF::init()
        range_info  Information about the next range 
    
    RETURN
      0 - The record combination satisfies the index condition
      1 - Otherwise
  */ 
  bool (*skip_index_tuple) (range_seq_t seq, char *range_info);
} RANGE_SEQ_IF;

uint16 &mrr_persistent_flag_storage(range_seq_t seq, uint idx);
char* &mrr_get_ptr_by_idx(range_seq_t seq, uint idx);

class Cost_estimate
{ 
private:
  double io_cost;                               
  double cpu_cost;                              
  double import_cost;                           
  double mem_cost;                              
  
public:

  static double IO_BLOCK_READ_COST() { return  1.0; } 

  Cost_estimate() :
    io_cost(0),
    cpu_cost(0),
    import_cost(0),
    mem_cost(0)
  {}

  double total_cost()      const { return io_cost + cpu_cost + import_cost; }
  double get_io_cost()     const { return io_cost; }
  double get_cpu_cost()    const { return cpu_cost; }
  double get_import_cost() const { return import_cost; }
  double get_mem_cost()    const { return mem_cost; }

  bool is_zero() const
  { 
    return !(io_cost || cpu_cost || import_cost || mem_cost);
  }

  void reset()
  {
    io_cost= cpu_cost= import_cost= mem_cost= 0;
  }

  void multiply(double m)
  {
    io_cost *= m;
    cpu_cost *= m;
    import_cost *= m;
    /* Don't multiply mem_cost */
  }

  Cost_estimate& operator+= (const Cost_estimate &other)
  {
    io_cost+= other.io_cost;
    cpu_cost+= other.cpu_cost;
    import_cost+= other.import_cost;
    mem_cost+= other.mem_cost;

    return *this;
  }

  Cost_estimate operator+ (const Cost_estimate &other)
  {
    Cost_estimate result= *this;
    result+= other;
    return result;
  }

  void add_io(double add_io_cost) { io_cost+= add_io_cost; }

  void add_cpu(double add_cpu_cost) { cpu_cost+= add_cpu_cost; }

  void add_import(double add_import_cost) { import_cost+= add_import_cost; }

  void add_mem(double add_mem_cost) { mem_cost+= add_mem_cost; }
};

void get_sweep_read_cost(TABLE *table, ha_rows nrows, bool interrupted, 
                         Cost_estimate *cost);

/*
  The below two are not used (and not handled) in this milestone of this WL
  entry because there seems to be no use for them at this stage of
  implementation.
*/
#define HA_MRR_SINGLE_POINT 1
#define HA_MRR_FIXED_KEY  2

/* 
  Indicates that RANGE_SEQ_IF::next(&range) doesn't need to fill in the
  'range' parameter.
*/
#define HA_MRR_NO_ASSOCIATION 4

/* 
  The MRR user will provide ranges in key order, and MRR implementation
  must return rows in key order.
  Passing this flag to multi_read_range_init() may cause the
  default MRR handler to be used even if HA_MRR_USE_DEFAULT_IMPL
  was not specified.
  (If the native MRR impl. can not provide SORTED result)
*/
#define HA_MRR_SORTED 8

/* MRR implementation doesn't have to retrieve full records */
#define HA_MRR_INDEX_ONLY 16

/* 
  The passed memory buffer is of maximum possible size, the caller can't
  assume larger buffer.
*/
#define HA_MRR_LIMITS 32


/*
  Flag set <=> default MRR implementation is used
  (The choice is made by **_info[_const]() function which may set this
   flag. SQL layer remembers the flag value and then passes it to
   multi_read_range_init().
*/
#define HA_MRR_USE_DEFAULT_IMPL 64

/*
  Used only as parameter to multi_range_read_info():
  Flag set <=> the caller guarantees that the bounds of the scanned ranges
  will not have NULL values.
*/
#define HA_MRR_NO_NULL_ENDPOINTS 128

/*
  Set by the MRR implementation to signal that it will natively
  produced sorted result if multi_range_read_init() is called with
  the HA_MRR_SORTED flag - Else multi_range_read_init(HA_MRR_SORTED)
  will revert to use the default MRR implementation. 
*/
#define HA_MRR_SUPPORT_SORTED 256


class ha_statistics
{
public:
  ulonglong data_file_length;           /* Length off data file */
  ulonglong max_data_file_length;       /* Length off data file */
  ulonglong index_file_length;
  ulonglong max_index_file_length;
  ulonglong delete_length;              /* Free bytes */
  ulonglong auto_increment_value;
  /*
    The number of records in the table. 
      0    - means the table has exactly 0 rows
    other  - if (table_flags() & HA_STATS_RECORDS_IS_EXACT)
               the value is the exact number of records in the table
             else
               it is an estimate
  */
  ha_rows records;
  ha_rows deleted;                      /* Deleted records */
  ulong mean_rec_length;                /* physical reclength */
  ulong create_time;                    /* When table was created */
  ulong check_time;
  ulong update_time;
  uint block_size;                      /* index block size */
  
  /*
    number of buffer bytes that native mrr implementation needs,
  */
  uint mrr_length_per_rec; 

  ha_statistics():
    data_file_length(0), max_data_file_length(0),
    index_file_length(0), delete_length(0), auto_increment_value(0),
    records(0), deleted(0), mean_rec_length(0), create_time(0),
    check_time(0), update_time(0), block_size(0)
  {}
};

uint calculate_key_len(TABLE *, uint, const uchar *, key_part_map);
/*
  bitmap with first N+1 bits set
  (keypart_map for a key prefix of [0..N] keyparts)
*/
#define make_keypart_map(N) (((key_part_map)2 << (N)) - 1)
/*
  bitmap with first N bits set
  (keypart_map for a key prefix of [0..N-1] keyparts)
*/
#define make_prev_keypart_map(N) (((key_part_map)1 << (N)) - 1)


class Handler_share
{
public:
  Handler_share() {}
  virtual ~Handler_share() {}
};


class handler :public Sql_alloc
{
public:
  typedef ulonglong Table_flags;
protected:
  TABLE_SHARE *table_share;             /* The table definition */
  TABLE *table;                         /* The current open table */
  Table_flags cached_table_flags;       /* Set on init() and open() */

  ha_rows estimation_rows_to_insert;
public:
  handlerton *ht;                 /* storage engine of this handler */
  uchar *ref;                           /* Pointer to current row */
  uchar *dup_ref;                       /* Pointer to duplicate row */

  ha_statistics stats;
  
  /* MultiRangeRead-related members: */
  range_seq_t mrr_iter;    /* Interator to traverse the range sequence */
  RANGE_SEQ_IF mrr_funcs;  /* Range sequence traversal functions */
  HANDLER_BUFFER *multi_range_buffer; /* MRR buffer info */
  uint ranges_in_seq; /* Total number of ranges in the traversed sequence */
  /* TRUE <=> source MRR ranges and the output are ordered */
  bool mrr_is_output_sorted;
  
  /* TRUE <=> we're currently traversing a range in mrr_cur_range. */
  bool mrr_have_range;
  /* Current range (the one we're now returning rows from) */
  KEY_MULTI_RANGE mrr_cur_range;

  /*
    The direction of the current range or index scan. This is used by
    the ICP implementation to determine if it has reached the end
    of the current range.
  */
  enum enum_range_scan_direction {
    RANGE_SCAN_ASC,
    RANGE_SCAN_DESC
  };
private:
  /*
    Storage space for the end range value. Should only be accessed using
    the end_range pointer. The content is invalid when end_range is NULL.
  */
  key_range save_end_range;
  enum_range_scan_direction range_scan_direction;
  int key_compare_result_on_equal;

protected:
  KEY_PART_INFO *range_key_part;
  bool eq_range;
  /* 
    TRUE <=> the engine guarantees that returned records are within the range
    being scanned.
  */
  bool in_range_check_pushed_down;

public:  
  /*
    End value for a range scan. If this is NULL the range scan has no
    end value. Should also be NULL when there is no ongoing range scan.
    Used by the read_range() functions and also evaluated by pushed
    index conditions.
  */
  key_range *end_range;
  uint errkey;                          /* Last dup key */
  uint key_used_on_scan;
  uint active_index;
  uint ref_length;
  FT_INFO *ft_handler;
  enum {NONE=0, INDEX, RND} inited;
  bool implicit_emptied;                /* Can be !=0 only if HEAP */
  const Item *pushed_cond;

  Item *pushed_idx_cond;
  uint pushed_idx_cond_keyno;  /* The index which the above condition is for */

  ulonglong next_insert_id;
  ulonglong insert_id_for_cur_row;
  Discrete_interval auto_inc_interval_for_cur_row;
  uint auto_inc_intervals_count;

  PSI_table *m_psi;

  virtual void unbind_psi();
  virtual void rebind_psi();

private:
  friend class DsMrr_impl;
  int m_lock_type;
  Handler_share **ha_share;

public:
  handler(handlerton *ht_arg, TABLE_SHARE *share_arg)
    :table_share(share_arg), table(0),
    estimation_rows_to_insert(0), ht(ht_arg),
    ref(0), range_scan_direction(RANGE_SCAN_ASC),
    in_range_check_pushed_down(false), end_range(NULL),
    key_used_on_scan(MAX_KEY), active_index(MAX_KEY),
    ref_length(sizeof(my_off_t)),
    ft_handler(0), inited(NONE),
    implicit_emptied(0),
    pushed_cond(0), pushed_idx_cond(NULL), pushed_idx_cond_keyno(MAX_KEY),
    next_insert_id(0), insert_id_for_cur_row(0),
    auto_inc_intervals_count(0),
    m_psi(NULL), m_lock_type(F_UNLCK), ha_share(NULL)
    {
      DBUG_PRINT("info",
                 ("handler created F_UNLCK %d F_RDLCK %d F_WRLCK %d",
                  F_UNLCK, F_RDLCK, F_WRLCK));
    }
  virtual ~handler(void)
  {
    DBUG_ASSERT(m_lock_type == F_UNLCK);
    DBUG_ASSERT(inited == NONE);
  }
  virtual handler *clone(const char *name, MEM_ROOT *mem_root);
  void init()
  {
    cached_table_flags= table_flags();
  }
  /* ha_ methods: public wrappers for private virtual API */

  int ha_open(TABLE *table, const char *name, int mode, int test_if_locked);
  int ha_close(void);
  int ha_index_init(uint idx, bool sorted);
  int ha_index_end();
  int ha_rnd_init(bool scan);
  int ha_rnd_end();
  int ha_rnd_next(uchar *buf);
  int ha_rnd_pos(uchar * buf, uchar *pos);
  int ha_index_read_map(uchar *buf, const uchar *key,
                        key_part_map keypart_map,
                        enum ha_rkey_function find_flag);
  int ha_index_read_last_map(uchar * buf, const uchar * key,
                             key_part_map keypart_map);
  int ha_index_read_idx_map(uchar *buf, uint index, const uchar *key,
                           key_part_map keypart_map,
                           enum ha_rkey_function find_flag);
  int ha_index_next(uchar * buf);
  int ha_index_prev(uchar * buf);
  int ha_index_first(uchar * buf);
  int ha_index_last(uchar * buf);
  int ha_index_next_same(uchar *buf, const uchar *key, uint keylen);
  int ha_index_read(uchar *buf, const uchar *key, uint key_len,
                    enum ha_rkey_function find_flag);
  int ha_index_read_last(uchar *buf, const uchar *key, uint key_len);
  int ha_reset();
  /* this is necessary in many places, e.g. in HANDLER command */
  int ha_index_or_rnd_end()
  {
    return inited == INDEX ? ha_index_end() : inited == RND ? ha_rnd_end() : 0;
  }
  Table_flags ha_table_flags() const { return cached_table_flags; }
  int ha_external_lock(THD *thd, int lock_type);
  int ha_write_row(uchar * buf);
  int ha_update_row(const uchar * old_data, uchar * new_data);
  int ha_delete_row(const uchar * buf);
  void ha_release_auto_increment();

  int check_collation_compatibility();
  int ha_check_for_upgrade(HA_CHECK_OPT *check_opt);
  int ha_check(THD *thd, HA_CHECK_OPT *check_opt);
  int ha_repair(THD* thd, HA_CHECK_OPT* check_opt);
  void ha_start_bulk_insert(ha_rows rows);
  int ha_end_bulk_insert();
  int ha_bulk_update_row(const uchar *old_data, uchar *new_data,
                         uint *dup_key_found);
  int ha_delete_all_rows();
  int ha_truncate();
  int ha_reset_auto_increment(ulonglong value);
  int ha_optimize(THD* thd, HA_CHECK_OPT* check_opt);
  int ha_analyze(THD* thd, HA_CHECK_OPT* check_opt);
  bool ha_check_and_repair(THD *thd);
  int ha_disable_indexes(uint mode);
  int ha_enable_indexes(uint mode);
  int ha_discard_or_import_tablespace(my_bool discard);
  int ha_rename_table(const char *from, const char *to);
  int ha_delete_table(const char *name);
  void ha_drop_table(const char *name);

  int ha_create(const char *name, TABLE *form, HA_CREATE_INFO *info);

  int ha_create_handler_files(const char *name, const char *old_name,
                              int action_flag, HA_CREATE_INFO *info);

  int ha_change_partitions(HA_CREATE_INFO *create_info,
                           const char *path,
                           ulonglong * const copied,
                           ulonglong * const deleted,
                           const uchar *pack_frm_data,
                           size_t pack_frm_len);
  int ha_drop_partitions(const char *path);
  int ha_rename_partitions(const char *path);

  void adjust_next_insert_id_after_explicit_value(ulonglong nr);
  int update_auto_increment();
  virtual void print_error(int error, myf errflag);
  virtual bool get_error_message(int error, String *buf);
  uint get_dup_key(int error);
  virtual bool get_foreign_dup_key(char *child_table_name,
                                   uint child_table_name_len,
                                   char *child_key_name,
                                   uint child_key_name_len)
  { DBUG_ASSERT(false); return(false); }
  virtual void change_table_ptr(TABLE *table_arg, TABLE_SHARE *share)
  {
    table= table_arg;
    table_share= share;
  }
  /* Estimates calculation */
  virtual double scan_time()
  { return ulonglong2double(stats.data_file_length) / IO_SIZE + 2; }


  virtual double read_time(uint index, uint ranges, ha_rows rows)
  { return rows2double(ranges+rows); }

  virtual double index_only_read_time(uint keynr, double records);
  
  virtual longlong get_memory_buffer_size() const { return -1; }

  virtual ha_rows multi_range_read_info_const(uint keyno, RANGE_SEQ_IF *seq,
                                              void *seq_init_param, 
                                              uint n_ranges, uint *bufsz,
                                              uint *flags, 
                                              Cost_estimate *cost);
  virtual ha_rows multi_range_read_info(uint keyno, uint n_ranges, uint keys,
                                        uint *bufsz, uint *flags, 
                                        Cost_estimate *cost);
  virtual int multi_range_read_init(RANGE_SEQ_IF *seq, void *seq_init_param,
                                    uint n_ranges, uint mode,
                                    HANDLER_BUFFER *buf);
  virtual int multi_range_read_next(char **range_info);


  virtual const key_map *keys_to_use_for_scanning() { return &key_map_empty; }
  bool has_transactions()
  { return (ha_table_flags() & HA_NO_TRANSACTIONS) == 0; }
  virtual uint extra_rec_buf_length() const { return 0; }

  virtual bool is_fatal_error(int error, uint flags)
  {
    if (!error ||
        ((flags & HA_CHECK_DUP_KEY) &&
         (error == HA_ERR_FOUND_DUPP_KEY ||
          error == HA_ERR_FOUND_DUPP_UNIQUE)))
      return FALSE;
    return TRUE;
  }

  virtual ha_rows records() { return stats.records; }
  virtual ha_rows estimate_rows_upper_bound()
  { return stats.records+EXTRA_RECORDS; }

  virtual enum row_type get_row_type() const { return ROW_TYPE_NOT_USED; }

  virtual const char *index_type(uint key_number) { DBUG_ASSERT(0); return "";}


  virtual void column_bitmaps_signal();
  uint get_index(void) const { return active_index; }

  virtual bool start_bulk_update() { return 1; }
  virtual bool start_bulk_delete() { return 1; }
  virtual int exec_bulk_update(uint *dup_key_found)
  {
    DBUG_ASSERT(FALSE);
    return HA_ERR_WRONG_COMMAND;
  }
  virtual void end_bulk_update() { return; }
  virtual int end_bulk_delete()
  {
    DBUG_ASSERT(FALSE);
    return HA_ERR_WRONG_COMMAND;
  }
protected:
  virtual int index_read_map(uchar * buf, const uchar * key,
                             key_part_map keypart_map,
                             enum ha_rkey_function find_flag)
  {
    uint key_len= calculate_key_len(table, active_index, key, keypart_map);
    return  index_read(buf, key, key_len, find_flag);
  }
  virtual int index_read_idx_map(uchar * buf, uint index, const uchar * key,
                                 key_part_map keypart_map,
                                 enum ha_rkey_function find_flag);
  virtual int index_next(uchar * buf)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_prev(uchar * buf)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_first(uchar * buf)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_last(uchar * buf)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_next_same(uchar *buf, const uchar *key, uint keylen);
  virtual int index_read_last_map(uchar * buf, const uchar * key,
                                  key_part_map keypart_map)
  {
    uint key_len= calculate_key_len(table, active_index, key, keypart_map);
    return index_read_last(buf, key, key_len);
  }
public:
  virtual int read_range_first(const key_range *start_key,
                               const key_range *end_key,
                               bool eq_range, bool sorted);
  virtual int read_range_next();

  void set_end_range(const key_range* range,
                     enum_range_scan_direction direction);
  int compare_key(key_range *range);
  int compare_key_icp(const key_range *range) const;
  virtual int ft_init() { return HA_ERR_WRONG_COMMAND; }
  void ft_end() { ft_handler=NULL; }
  virtual FT_INFO *ft_init_ext(uint flags, uint inx,String *key)
    { return NULL; }
  virtual int ft_read(uchar *buf) { return HA_ERR_WRONG_COMMAND; }
protected:
  virtual int rnd_next(uchar *buf)=0;
  virtual int rnd_pos(uchar * buf, uchar *pos)=0;
public:
  virtual int rnd_pos_by_record(uchar *record)
    {
      DBUG_ASSERT(table_flags() & HA_PRIMARY_KEY_REQUIRED_FOR_POSITION);
      position(record);
      return ha_rnd_pos(record, ref);
    }
  virtual int read_first_row(uchar *buf, uint primary_key);
  virtual int restart_rnd_next(uchar *buf, uchar *pos)
    { return HA_ERR_WRONG_COMMAND; }
  virtual int rnd_same(uchar *buf, uint inx)
    { return HA_ERR_WRONG_COMMAND; }
  virtual ha_rows records_in_range(uint inx, key_range *min_key, key_range *max_key)
    { return (ha_rows) 10; }
  /*
    If HA_PRIMARY_KEY_REQUIRED_FOR_POSITION is set, then it sets ref
    (reference to the row, aka position, with the primary key given in
    the record).
    Otherwise it set ref to the current row.
  */
  virtual void position(const uchar *record)=0;
  virtual int info(uint)=0; // see my_base.h for full description
  virtual void get_dynamic_partition_info(PARTITION_STATS *stat_info,
                                          uint part_id);
  virtual uint32 calculate_key_hash_value(Field **field_array)
  { DBUG_ASSERT(0); return 0; }
  virtual int extra(enum ha_extra_function operation)
  { return 0; }
  virtual int extra_opt(enum ha_extra_function operation, ulong cache_size)
  { return extra(operation); }

  virtual bool start_read_removal(void)
  { DBUG_ASSERT(0); return false; }

  virtual ha_rows end_read_removal(void)
  { DBUG_ASSERT(0); return (ha_rows) 0; }

  virtual bool was_semi_consistent_read() { return 0; }
  virtual void try_semi_consistent_read(bool) {}
  virtual void unlock_row() {}
  virtual int start_stmt(THD *thd, thr_lock_type lock_type) {return 0;}
  virtual void get_auto_increment(ulonglong offset, ulonglong increment,
                                  ulonglong nb_desired_values,
                                  ulonglong *first_value,
                                  ulonglong *nb_reserved_values);
  void set_next_insert_id(ulonglong id)
  {
    DBUG_PRINT("info",("auto_increment: next value %lu", (ulong)id));
    next_insert_id= id;
  }
  void restore_auto_increment(ulonglong prev_insert_id)
  {
    /*
      Insertion of a row failed, re-use the lastly generated auto_increment
      id, for the next row. This is achieved by resetting next_insert_id to
      what it was before the failed insertion (that old value is provided by
      the caller). If that value was 0, it was the first row of the INSERT;
      then if insert_id_for_cur_row contains 0 it means no id was generated
      for this first row, so no id was generated since the INSERT started, so
      we should set next_insert_id to 0; if insert_id_for_cur_row is not 0, it
      is the generated id of the first and failed row, so we use it.
    */
    next_insert_id= (prev_insert_id > 0) ? prev_insert_id :
      insert_id_for_cur_row;
  }

  virtual void update_create_info(HA_CREATE_INFO *create_info) {}
  int check_old_types();
  virtual int assign_to_keycache(THD* thd, HA_CHECK_OPT* check_opt)
  { return HA_ADMIN_NOT_IMPLEMENTED; }
  virtual int preload_keys(THD* thd, HA_CHECK_OPT* check_opt)
  { return HA_ADMIN_NOT_IMPLEMENTED; }
  /* end of the list of admin commands */

  virtual int indexes_are_disabled(void) {return 0;}
  virtual char *update_table_comment(const char * comment)
  { return (char*) comment;}
  virtual void append_create_info(String *packet) {}
  virtual bool is_fk_defined_on_table_or_index(uint index)
  { return FALSE; }
  virtual char* get_foreign_key_create_info()
  { return(NULL);}  /* gets foreign key create string from InnoDB */
  virtual bool can_switch_engines() { return true; }
  virtual int
  get_foreign_key_list(THD *thd, List<FOREIGN_KEY_INFO> *f_key_list)
  { return 0; }
  virtual int
  get_parent_foreign_key_list(THD *thd, List<FOREIGN_KEY_INFO> *f_key_list)
  { return 0; }
  virtual uint referenced_by_foreign_key() { return 0;}
  virtual void init_table_handle_for_HANDLER()
  { return; }       /* prepare InnoDB for HANDLER */
  virtual void free_foreign_key_create_info(char* str) {}
  virtual const char *table_type() const =0;
  virtual const char **bas_ext() const =0;

  virtual int get_default_no_partitions(HA_CREATE_INFO *info) { return 1;}
  virtual void set_auto_partitions(partition_info *part_info) { return; }

  virtual bool get_no_parts(const char *name,
                            uint *no_parts)
  {
    *no_parts= 0;
    return 0;
  }
  virtual void set_part_info(partition_info *part_info, bool early) {return;}

  virtual ulong index_flags(uint idx, uint part, bool all_parts) const =0;

  uint max_record_length() const
  {
    using std::min;
    return min(HA_MAX_REC_LENGTH, max_supported_record_length());
  }
  uint max_keys() const
  {
    using std::min;
    return min(MAX_KEY, max_supported_keys());
  }
  uint max_key_parts() const
  {
    using std::min;
    return min(MAX_REF_PARTS, max_supported_key_parts());
  }
  uint max_key_length() const
  {
    using std::min;
    return min(MAX_KEY_LENGTH, max_supported_key_length());
  }
  uint max_key_part_length() const
  {
    using std::min;
    return min(MAX_KEY_LENGTH, max_supported_key_part_length());
  }

  virtual uint max_supported_record_length() const { return HA_MAX_REC_LENGTH; }
  virtual uint max_supported_keys() const { return 0; }
  virtual uint max_supported_key_parts() const { return MAX_REF_PARTS; }
  virtual uint max_supported_key_length() const { return MAX_KEY_LENGTH; }
  virtual uint max_supported_key_part_length() const { return 255; }
  virtual uint min_record_length(uint options) const { return 1; }

  virtual bool low_byte_first() const { return 1; }
  virtual uint checksum() const { return 0; }
  virtual bool is_crashed() const  { return 0; }
  virtual bool auto_repair() const { return 0; }


#define CHF_CREATE_FLAG 0
#define CHF_DELETE_FLAG 1
#define CHF_RENAME_FLAG 2
#define CHF_INDEX_FLAG  3


  virtual uint lock_count(void) const { return 1; }
  virtual THR_LOCK_DATA **store_lock(THD *thd,
                                     THR_LOCK_DATA **to,
                                     enum thr_lock_type lock_type)=0;

  virtual uint8 table_cache_type() { return HA_CACHE_TBL_NONTRANSACT; }


  virtual my_bool register_query_cache_table(THD *thd, char *table_key,
                                             uint key_length,
                                             qc_engine_callback
                                             *engine_callback,
                                             ulonglong *engine_data)
  {
    *engine_callback= 0;
    return TRUE;
  }


 /*
   @retval TRUE   Primary key (if there is one) is clustered
                  key covering all fields
   @retval FALSE  otherwise
 */
 virtual bool primary_key_is_clustered() { return FALSE; }
 virtual int cmp_ref(const uchar *ref1, const uchar *ref2)
 {
   return memcmp(ref1, ref2, ref_length);
 }

 /*
   Condition pushdown to storage engines
 */

 virtual const Item *cond_push(const Item *cond) { return cond; };
 virtual void cond_pop() { return; }

 virtual Item *idx_cond_push(uint keyno, Item* idx_cond) { return idx_cond; }

 virtual void cancel_pushed_idx_cond()
 {
   pushed_idx_cond= NULL;
   pushed_idx_cond_keyno= MAX_KEY;
   in_range_check_pushed_down= false;
 }

  virtual uint number_of_pushed_joins() const
  { return 0; }

  virtual const TABLE* root_of_pushed_join() const
  { return NULL; }

  virtual const TABLE* parent_of_pushed_join() const
  { return NULL; }

  virtual int index_read_pushed(uchar * buf, const uchar * key,
                             key_part_map keypart_map)
  { return  HA_ERR_WRONG_COMMAND; }

  virtual int index_next_pushed(uchar * buf)
  { return  HA_ERR_WRONG_COMMAND; }

 virtual bool check_if_incompatible_data(HA_CREATE_INFO *create_info,
                                         uint table_changes)
 { return COMPATIBLE_DATA_NO; }

 /* On-line/in-place ALTER TABLE interface. */

 /*
   Here is an outline of on-line/in-place ALTER TABLE execution through
   this interface.

   Phase 1 : Initialization
   ========================
   During this phase we determine which algorithm should be used
   for execution of ALTER TABLE and what level concurrency it will
   require.

   *) This phase starts by opening the table and preparing description
      of the new version of the table.
   *) Then we check if it is impossible even in theory to carry out
      this ALTER TABLE using the in-place algorithm. For example, because
      we need to change storage engine or the user has explicitly requested
      usage of the "copy" algorithm.
   *) If in-place ALTER TABLE is theoretically possible, we continue
      by compiling differences between old and new versions of the table
      in the form of HA_ALTER_FLAGS bitmap. We also build a few
      auxiliary structures describing requested changes and store
      all these data in the Alter_inplace_info object.
   *) Then the handler::check_if_supported_inplace_alter() method is called
      in order to find if the storage engine can carry out changes requested
      by this ALTER TABLE using the in-place algorithm. To determine this,
      the engine can rely on data in HA_ALTER_FLAGS/Alter_inplace_info
      passed to it as well as on its own checks. If the in-place algorithm
      can be used for this ALTER TABLE, the level of required concurrency for
      its execution is also returned.
      If any errors occur during the handler call, ALTER TABLE is aborted
      and no further handler functions are called.
   *) Locking requirements of the in-place algorithm are compared to any
      concurrency requirements specified by user. If there is a conflict
      between them, we either switch to the copy algorithm or emit an error.

   Phase 2 : Execution
   ===================

   In this phase the operations are executed.

   *) As the first step, we acquire a lock corresponding to the concurrency
      level which was returned by handler::check_if_supported_inplace_alter()
      and requested by the user. This lock is held for most of the
      duration of in-place ALTER (if HA_ALTER_INPLACE_SHARED_LOCK_AFTER_PREPARE
      or HA_ALTER_INPLACE_NO_LOCK_AFTER_PREPARE were returned we acquire an
      exclusive lock for duration of the next step only).
   *) After that we call handler::ha_prepare_inplace_alter_table() to give the
      storage engine a chance to update its internal structures with a higher
      lock level than the one that will be used for the main step of algorithm.
      After that we downgrade the lock if it is necessary.
   *) After that, the main step of this phase and algorithm is executed.
      We call the handler::ha_inplace_alter_table() method, which carries out the
      changes requested by ALTER TABLE but does not makes them visible to other
      connections yet.
   *) We ensure that no other connection uses the table by upgrading our
      lock on it to exclusive.
   *) a) If the previous step succeeds, handler::ha_commit_inplace_alter_table() is
         called to allow the storage engine to do any final updates to its structures,
         to make all earlier changes durable and visible to other connections.
      b) If we have failed to upgrade lock or any errors have occured during the
         handler functions calls (including commit), we call
         handler::ha_commit_inplace_alter_table()
         to rollback all changes which were done during previous steps.

  Phase 3 : Final
  ===============

  In this phase we:

  *) Update SQL-layer data-dictionary by installing .FRM file for the new version
     of the table.
  *) Inform the storage engine about this change by calling the
     handler::ha_notify_table_changed() method.
  *) Destroy the Alter_inplace_info and handler_ctx objects.

 */

 virtual enum_alter_inplace_result
 check_if_supported_inplace_alter(TABLE *altered_table,
                                  Alter_inplace_info *ha_alter_info);


 bool ha_prepare_inplace_alter_table(TABLE *altered_table,
                                     Alter_inplace_info *ha_alter_info);


 bool ha_inplace_alter_table(TABLE *altered_table,
                             Alter_inplace_info *ha_alter_info)
 {
   return inplace_alter_table(altered_table, ha_alter_info);
 }


 bool ha_commit_inplace_alter_table(TABLE *altered_table,
                                    Alter_inplace_info *ha_alter_info,
                                    bool commit);


 void ha_notify_table_changed()
 {
   notify_table_changed();
 }


protected:
 virtual bool prepare_inplace_alter_table(TABLE *altered_table,
                                          Alter_inplace_info *ha_alter_info)
 { return false; }


 virtual bool inplace_alter_table(TABLE *altered_table,
                                  Alter_inplace_info *ha_alter_info)
 { return false; }


 virtual bool commit_inplace_alter_table(TABLE *altered_table,
                                         Alter_inplace_info *ha_alter_info,
                                         bool commit)
{
  /* Nothing to commit/rollback, mark all handlers committed! */
  ha_alter_info->group_commit_ctx= NULL;
  return false;
}


 virtual void notify_table_changed();

public:
 /* End of On-line/in-place ALTER TABLE interface. */


  virtual void use_hidden_primary_key();
  virtual uint alter_table_flags(uint flags)
  {
    if (ht->alter_table_flags)
      return ht->alter_table_flags(flags);
    return 0;
  }

protected:
  /* Service methods for use by storage engines. */
  void ha_statistic_increment(ulonglong SSV::*offset) const;
  void **ha_data(THD *) const;
  THD *ha_thd(void) const;

  PSI_table_share *ha_table_share_psi(const TABLE_SHARE *share) const;

  virtual int rename_table(const char *from, const char *to);
  virtual int delete_table(const char *name);
private:
  /* Private helpers */
  inline void mark_trx_read_write();
  /*
    Low-level primitives for storage engines.  These should be
    overridden by the storage engine class. To call these methods, use
    the corresponding 'ha_*' method above.
  */

  virtual int open(const char *name, int mode, uint test_if_locked)=0;
  virtual int close(void)=0;
  virtual int index_init(uint idx, bool sorted) { active_index= idx; return 0; }
  virtual int index_end() { active_index= MAX_KEY; return 0; }
  virtual int rnd_init(bool scan)= 0;
  virtual int rnd_end() { return 0; }
  virtual int write_row(uchar *buf __attribute__((unused)))
  {
    return HA_ERR_WRONG_COMMAND;
  }

  virtual int update_row(const uchar *old_data __attribute__((unused)),
                         uchar *new_data __attribute__((unused)))
  {
    return HA_ERR_WRONG_COMMAND;
  }

  virtual int delete_row(const uchar *buf __attribute__((unused)))
  {
    return HA_ERR_WRONG_COMMAND;
  }
  virtual int reset() { return 0; }
  virtual Table_flags table_flags(void) const= 0;
  virtual int external_lock(THD *thd __attribute__((unused)),
                            int lock_type __attribute__((unused)))
  {
    return 0;
  }
  virtual void release_auto_increment() { return; };
  virtual int check_for_upgrade(HA_CHECK_OPT *check_opt)
  { return 0; }
  virtual int check(THD* thd, HA_CHECK_OPT* check_opt)
  { return HA_ADMIN_NOT_IMPLEMENTED; }

  virtual int repair(THD* thd, HA_CHECK_OPT* check_opt)
  {
    DBUG_ASSERT(!(ha_table_flags() & HA_CAN_REPAIR));
    return HA_ADMIN_NOT_IMPLEMENTED;
  }
  virtual void start_bulk_insert(ha_rows rows) {}
  virtual int end_bulk_insert() { return 0; }
protected:
  virtual int index_read(uchar * buf, const uchar * key, uint key_len,
                         enum ha_rkey_function find_flag)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_read_last(uchar * buf, const uchar * key, uint key_len)
   { return (my_errno= HA_ERR_WRONG_COMMAND); }
public:
  virtual int bulk_update_row(const uchar *old_data, uchar *new_data,
                              uint *dup_key_found)
  {
    DBUG_ASSERT(FALSE);
    return HA_ERR_WRONG_COMMAND;
  }
  virtual int delete_all_rows()
  { return (my_errno=HA_ERR_WRONG_COMMAND); }
  virtual int truncate()
  { return HA_ERR_WRONG_COMMAND; }
  virtual int reset_auto_increment(ulonglong value)
  { return HA_ERR_WRONG_COMMAND; }
  virtual int optimize(THD* thd, HA_CHECK_OPT* check_opt)
  { return HA_ADMIN_NOT_IMPLEMENTED; }
  virtual int analyze(THD* thd, HA_CHECK_OPT* check_opt)
  { return HA_ADMIN_NOT_IMPLEMENTED; }
  virtual bool check_and_repair(THD *thd) { return TRUE; }
  virtual int disable_indexes(uint mode) { return HA_ERR_WRONG_COMMAND; }
  virtual int enable_indexes(uint mode) { return HA_ERR_WRONG_COMMAND; }
  virtual int discard_or_import_tablespace(my_bool discard)
  { return (my_errno=HA_ERR_WRONG_COMMAND); }
  virtual void drop_table(const char *name);
  virtual int create(const char *name, TABLE *form, HA_CREATE_INFO *info)=0;

  virtual int create_handler_files(const char *name, const char *old_name,
                                   int action_flag, HA_CREATE_INFO *info)
  { return FALSE; }

  virtual int change_partitions(HA_CREATE_INFO *create_info,
                                const char *path,
                                ulonglong * const copied,
                                ulonglong * const deleted,
                                const uchar *pack_frm_data,
                                size_t pack_frm_len)
  { return HA_ERR_WRONG_COMMAND; }
  virtual int drop_partitions(const char *path)
  { return HA_ERR_WRONG_COMMAND; }
  virtual int rename_partitions(const char *path)
  { return HA_ERR_WRONG_COMMAND; }
  virtual bool set_ha_share_ref(Handler_share **arg_ha_share)
  {
    DBUG_ASSERT(!ha_share);
    DBUG_ASSERT(arg_ha_share);
    if (ha_share || !arg_ha_share)
      return true;
    ha_share= arg_ha_share;
    return false;
  }
  int get_lock_type() const { return m_lock_type; }
protected:
  Handler_share *get_ha_share_ptr();
  void set_ha_share_ptr(Handler_share *arg_ha_share);
  void lock_shared_ha_data();
  void unlock_shared_ha_data();
};


bool key_uses_partial_cols(TABLE *table, uint keyno);

/*
  A Disk-Sweep MRR interface implementation

  This implementation makes range (and, in the future, 'ref') scans to read
  table rows in disk sweeps. 
  
  Currently it is used by MyISAM and InnoDB. Potentially it can be used with
  any table handler that has non-clustered indexes and on-disk rows.
*/

class DsMrr_impl
{
public:
  typedef void (handler::*range_check_toggle_func_t)(bool on);

  DsMrr_impl()
    : h2(NULL) {};
  ~DsMrr_impl() { DBUG_ASSERT(h2 == NULL); }
  
  /*
    The "owner" handler object (the one that calls dsmrr_XXX functions.
    It is used to retrieve full table rows by calling rnd_pos().
  */
  handler *h;
  TABLE *table; /* Always equal to h->table */
private:
  /* Secondary handler object.  It is used for scanning the index */
  handler *h2;

  /* Buffer to store rowids, or (rowid, range_id) pairs */
  uchar *rowids_buf;
  uchar *rowids_buf_cur;   /* Current position when reading/writing */
  uchar *rowids_buf_last;  /* When reading: end of used buffer space */
  uchar *rowids_buf_end;   /* End of the buffer */

  bool dsmrr_eof; /* TRUE <=> We have reached EOF when reading index tuples */

  /* TRUE <=> need range association, buffer holds {rowid, range_id} pairs */
  bool is_mrr_assoc;

  bool use_default_impl; /* TRUE <=> shortcut all calls to default MRR impl */
public:
  void init(handler *h_arg, TABLE *table_arg)
  {
    h= h_arg; 
    table= table_arg;
  }
  int dsmrr_init(handler *h, RANGE_SEQ_IF *seq_funcs, void *seq_init_param, 
                 uint n_ranges, uint mode, HANDLER_BUFFER *buf);
  void dsmrr_close();

  void reset();
  int dsmrr_fill_buffer();
  int dsmrr_next(char **range_info);

  ha_rows dsmrr_info(uint keyno, uint n_ranges, uint keys, uint *bufsz,
                     uint *flags, Cost_estimate *cost);

  ha_rows dsmrr_info_const(uint keyno, RANGE_SEQ_IF *seq, 
                            void *seq_init_param, uint n_ranges, uint *bufsz,
                            uint *flags, Cost_estimate *cost);
private:
  bool choose_mrr_impl(uint keyno, ha_rows rows, uint *flags, uint *bufsz, 
                       Cost_estimate *cost);
  bool get_disk_sweep_mrr_cost(uint keynr, ha_rows rows, uint flags, 
                               uint *buffer_size, Cost_estimate *cost);
};
        /* Some extern variables used with handlers */

extern const char *ha_row_type[];
extern MYSQL_PLUGIN_IMPORT const char *tx_isolation_names[];
extern MYSQL_PLUGIN_IMPORT const char *binlog_format_names[];
extern TYPELIB tx_isolation_typelib;
extern const char *myisam_stats_method_names[];
extern ulong total_ha, total_ha_2pc;

/* lookups */
handlerton *ha_default_handlerton(THD *thd);
handlerton *ha_default_temp_handlerton(THD *thd);
plugin_ref ha_resolve_by_name(THD *thd, const LEX_STRING *name, 
                              bool is_temp_table);
plugin_ref ha_lock_engine(THD *thd, const handlerton *hton);
handlerton *ha_resolve_by_legacy_type(THD *thd, enum legacy_db_type db_type);
handler *get_new_handler(TABLE_SHARE *share, MEM_ROOT *alloc,
                         handlerton *db_type);
handlerton *ha_checktype(THD *thd, enum legacy_db_type database_type,
                          bool no_substitute, bool report_error);


static inline enum legacy_db_type ha_legacy_type(const handlerton *db_type)
{
  return (db_type == NULL) ? DB_TYPE_UNKNOWN : db_type->db_type;
}

static inline const char *ha_resolve_storage_engine_name(const handlerton *db_type)
{
  return db_type == NULL ? "UNKNOWN" : hton2plugin[db_type->slot]->name.str;
}

static inline bool ha_check_storage_engine_flag(const handlerton *db_type, uint32 flag)
{
  return db_type == NULL ? FALSE : test(db_type->flags & flag);
}

static inline bool ha_storage_engine_is_enabled(const handlerton *db_type)
{
  return (db_type && db_type->create) ?
         (db_type->state == SHOW_OPTION_YES) : FALSE;
}

/* basic stuff */
int ha_init_errors(void);
int ha_init(void);
int ha_end(void);
int ha_initialize_handlerton(st_plugin_int *plugin);
int ha_finalize_handlerton(st_plugin_int *plugin);

TYPELIB* ha_known_exts();
int ha_panic(enum ha_panic_function flag);
void ha_close_connection(THD* thd);
bool ha_flush_logs(handlerton *db_type);
void ha_drop_database(char* path);
int ha_create_table(THD *thd, const char *path,
                    const char *db, const char *table_name,
                    HA_CREATE_INFO *create_info,
                                bool update_create_info,
                    bool is_temp_table= false);

int ha_delete_table(THD *thd, handlerton *db_type, const char *path,
                    const char *db, const char *alias, bool generate_warning);

/* statistics and info */
bool ha_show_status(THD *thd, handlerton *db_type, enum ha_stat_type stat);

/* discovery */
int ha_create_table_from_engine(THD* thd, const char *db, const char *name);
bool ha_check_if_table_exists(THD* thd, const char *db, const char *name,
                             bool *exists);
int ha_discover(THD* thd, const char* dbname, const char* name,
                uchar** frmblob, size_t* frmlen);
int ha_find_files(THD *thd,const char *db,const char *path,
                  const char *wild, bool dir, List<LEX_STRING>* files);
int ha_table_exists_in_engine(THD* thd, const char* db, const char* name);
bool ha_check_if_supported_system_table(handlerton *hton, const char* db, 
                                        const char* table_name);

/* key cache */
extern "C" int ha_init_key_cache(const char *name, KEY_CACHE *key_cache);
int ha_resize_key_cache(KEY_CACHE *key_cache);
int ha_change_key_cache_param(KEY_CACHE *key_cache);
int ha_change_key_cache(KEY_CACHE *old_key_cache, KEY_CACHE *new_key_cache);

/* report to InnoDB that control passes to the client */
int ha_release_temporary_latches(THD *thd);

/* transactions: interface to handlerton functions */
int ha_start_consistent_snapshot(THD *thd);
int ha_commit_or_rollback_by_xid(THD *thd, XID *xid, bool commit);
int ha_commit_trans(THD *thd, bool all, bool ignore_global_read_lock= false);
int ha_rollback_trans(THD *thd, bool all);
int ha_prepare(THD *thd);
int ha_recover(HASH *commit_list);

/*
 transactions: interface to low-level handlerton functions. These are
 intended to be used by the transaction coordinators to
 commit/prepare/rollback transactions in the engines.
*/
int ha_commit_low(THD *thd, bool all, bool run_after_commit= true);
int ha_prepare_low(THD *thd, bool all);
int ha_rollback_low(THD *thd, bool all);

/* transactions: these functions never call handlerton functions directly */
int ha_enable_transaction(THD *thd, bool on);

/* savepoints */
int ha_rollback_to_savepoint(THD *thd, SAVEPOINT *sv);
int ha_savepoint(THD *thd, SAVEPOINT *sv);
int ha_release_savepoint(THD *thd, SAVEPOINT *sv);

/* Build pushed joins in handlers implementing this feature */
int ha_make_pushed_joins(THD *thd, const AQP::Join_plan* plan);

/* these are called by storage engines */
void trans_register_ha(THD *thd, bool all, handlerton *ht);

/*
  Storage engine has to assume the transaction will end up with 2pc if
   - there is more than one 2pc-capable storage engine available
   - in the current transaction 2pc was not disabled yet
*/
#define trans_need_2pc(thd, all)                   ((total_ha_2pc > 1) && \
        !((all ? &thd->transaction.all : &thd->transaction.stmt)->no_2pc))

#ifdef HAVE_NDB_BINLOG
int ha_reset_logs(THD *thd);
int ha_binlog_index_purge_file(THD *thd, const char *file);
void ha_reset_slave(THD *thd);
void ha_binlog_log_query(THD *thd, handlerton *db_type,
                         enum_binlog_command binlog_command,
                         const char *query, uint query_length,
                         const char *db, const char *table_name);
void ha_binlog_wait(THD *thd);
#else
#define ha_reset_logs(a) do {} while (0)
#define ha_binlog_index_purge_file(a,b) do {} while (0)
#define ha_reset_slave(a) do {} while (0)
#define ha_binlog_log_query(a,b,c,d,e,f,g) do {} while (0)
#define ha_binlog_wait(a) do {} while (0)
#endif

/* It is required by basic binlog features on both MySQL server and libmysqld */
int ha_binlog_end(THD *thd);

const char *ha_legacy_type_name(legacy_db_type legacy_type);
const char *get_canonical_filename(handler *file, const char *path,
                                   char *tmp_path);
bool mysql_xa_recover(THD *thd);


inline const char *table_case_name(HA_CREATE_INFO *info, const char *name)
{
  return ((lower_case_table_names == 2 && info->alias) ? info->alias : name);
}

void print_keydup_error(TABLE *table, KEY *key, const char *msg, myf errflag);
void print_keydup_error(TABLE *table, KEY *key, myf errflag);

#endif /* HANDLER_INCLUDED */