path: root/sql/handler.h

/* Copyright (C) 2000-2006 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; 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


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

#ifdef USE_PRAGMA_INTERFACE
#pragma interface			/* gcc class implementation */
#endif

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

#ifndef NO_HASH
#define NO_HASH				/* Not yet implemented */
#endif

#if defined(HAVE_BERKELEY_DB) || defined(HAVE_INNOBASE_DB) || \
    defined(HAVE_NDBCLUSTER_DB)
#define USING_TRANSACTIONS
#endif

// 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

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

/*
  Can switch index during the scan with ::rnd_same() - not used yet.
  see mi_rsame/heap_rsame/myrg_rsame
*/
#define HA_READ_RND_SAME       (1 << 0)
#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 */
#define HA_REC_NOT_IN_SEQ      (1 << 3) /* ha_info don't return recnumber;
                                           It returns a position to ha_r_rnd */
#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)
#define HA_NULL_IN_KEY         (1 << 7) /* One can have keys with NULL */
#define HA_DUPP_POS            (1 << 8) /* ha_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_NOT_EXACT_COUNT     (1 << 13)
/*
  INSERT_DELAYED only works with handlers that uses MySQL internal table
  level locks
*/
#define HA_CAN_INSERT_DELAYED  (1 << 14)
#define HA_PRIMARY_KEY_IN_READ_INDEX (1 << 15)
#define HA_CAN_RTREEKEYS       (1 << 17)
#define HA_NOT_DELETE_WITH_CACHE (1 << 18)
#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_NEED_READ_RANGE_BUFFER (1 << 29) /* for read_multi_range */
#define HA_ANY_INDEX_MAY_BE_UNIQUE (1 << 30)


/* 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


/* 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)
*/
#define MAX_HA 14

/*
  Bits in index_ddl_flags(KEY *wanted_index)
  for what ddl you can do with index
  If none is set, the wanted type of index is not supported
  by the handler at all. See WorkLog 1563.
*/
#define HA_DDL_SUPPORT   1 /* Supported by handler */
#define HA_DDL_WITH_LOCK 2 /* Can create/drop with locked table */
#define HA_DDL_ONLINE    4 /* Can create/drop without lock */

/*
  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

	/* Errors on write which is recoverable  (Key exist) */
#define HA_WRITE_SKIP 121		/* Duplicate key on write */
#define HA_READ_CHECK 123		/* Update with is recoverable */
#define HA_CANT_DO_THAT 131		/* Databasehandler can't do it */

	/* 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_OPTION_NO_CHECKSUM	(1L << 17)
#define HA_OPTION_NO_DELAY_KEY_WRITE (1L << 18)
#define HA_MAX_REC_LENGTH	65535

/* 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

/* Options of START TRANSACTION statement (and later of SET TRANSACTION stmt) */
#define MYSQL_START_TRANS_OPT_WITH_CONS_SNAPSHOT 1

enum 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_DEFAULT // 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 };

/* 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)
#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)

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 128
#define MAXGTRIDSIZE 64
#define MAXBQUALSIZE 64

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_LEN, &server_id, sizeof(server_id)) &&
           !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;
  }
  byte *key()
  {
    return (byte *)&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
#ifdef SAFEMALLOC
#define MAX_XID_LIST_SIZE  256
#else
#define MAX_XID_LIST_SIZE  (1024*128)
#endif

/*
  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.
*/
typedef struct
{
  /*
    storage engine name as it should be printed to a user
  */
  const char *name;

  /*
    Historical marker for if the engine is available of not
  */
  SHOW_COMP_OPTION state;

  /*
    A comment used by SHOW to describe an engine.
  */
  const char *comment;

  /*
    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 db_type db_type;
  /*
    Method that initizlizes a storage engine
  */
  bool (*init)();

  /*
    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)(THD *thd);
   /*
     sv points to an uninitialized storage area of requested size
     (see savepoint_offset description)
   */
   int  (*savepoint_set)(THD *thd, void *sv);
   /*
     sv points to a storage area, that was earlier passed
     to the savepoint_set call
   */
   int  (*savepoint_rollback)(THD *thd, void *sv);
   int  (*savepoint_release)(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)(THD *thd, bool all);
   int  (*rollback)(THD *thd, bool all);
   int  (*prepare)(THD *thd, bool all);
   int  (*recover)(XID *xid_list, uint len);
   int  (*commit_by_xid)(XID *xid);
   int  (*rollback_by_xid)(XID *xid);
   void *(*create_cursor_read_view)();
   void (*set_cursor_read_view)(void *);
   void (*close_cursor_read_view)(void *);
   uint32 flags;                                /* global handler flags */
} handlerton;

struct show_table_alias_st {
  const char *alias;
  const char *type;
};

/* Possible flags of a handlerton */
#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

typedef struct st_thd_trans
{
  /* number of entries in the ht[] */
  uint        nht;
  /* true is not all entries in the ht[] support 2pc */
  bool        no_2pc;
  /* storage engines that registered themselves for this transaction */
  handlerton *ht[MAX_HA];
} THD_TRANS;

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

typedef struct st_ha_create_information
{
  CHARSET_INFO *table_charset, *default_table_charset;
  LEX_STRING connect_string;
  LEX_STRING comment;
  const char *password;
  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 raid_chunksize;
  ulong used_fields;
  SQL_LIST merge_list;
  enum db_type db_type;
  enum row_type row_type;
  uint null_bits;                       /* NULL bits at start of record */
  uint options;				/* OR of HA_CREATE_ options */
  uint raid_type,raid_chunks;
  uint merge_insert_method;
  uint extra_size;                      /* length of extra data segment */
  bool table_existed;			/* 1 in create if table existed */
  bool frm_only;                        /* 1 if no ha_create_table() */
  bool varchar;                         /* 1 if table has a VARCHAR */
} HA_CREATE_INFO;


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

struct st_table;
typedef struct st_table TABLE;
struct st_foreign_key_info;
typedef struct st_foreign_key_info FOREIGN_KEY_INFO;

typedef struct st_savepoint SAVEPOINT;
extern ulong savepoint_alloc_size;

/* Forward declaration for condition pushdown to storage engine */
typedef class Item COND;

typedef struct st_ha_check_opt
{
  st_ha_check_opt() {}                        /* Remove gcc warning */
  ulong sort_buffer_size;
  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
{
  const byte *buffer;         /* Buffer one can start using */
  const byte *buffer_end;     /* End of buffer */
  byte *end_of_used_area;     /* End of area that was used by handler */
} HANDLER_BUFFER;


class handler :public Sql_alloc
{
 protected:
  struct st_table *table;		/* The table definition */

  virtual int index_init(uint idx) { active_index=idx; return 0; }
  virtual int index_end() { active_index=MAX_KEY; return 0; }
  /*
    rnd_init() can be called two times without rnd_end() in between
    (it only makes sense if scan=1).
    then the second call should prepare for the new table scan (e.g
    if rnd_init allocates the cursor, second call should position it
    to the start of the table, no need to deallocate and allocate it again
  */
  virtual int rnd_init(bool scan) =0;
  virtual int rnd_end() { return 0; }

public:
  const handlerton *ht;                 /* storage engine of this handler */
  byte *ref;				/* Pointer to current row */
  byte *dupp_ref;			/* Pointer to dupp row */
  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;
  ha_rows records;			/* Records in table */
  ha_rows deleted;			/* Deleted records */
  ulong raid_chunksize;
  ulong mean_rec_length;		/* physical reclength */
  time_t create_time;			/* When table was created */
  time_t check_time;
  time_t update_time;

  /* The following are for read_multi_range */
  bool multi_range_sorted;
  KEY_MULTI_RANGE *multi_range_curr;
  KEY_MULTI_RANGE *multi_range_end;
  HANDLER_BUFFER *multi_range_buffer;

  /* The following are for read_range() */
  key_range save_end_range, *end_range;
  KEY_PART_INFO *range_key_part;
  int key_compare_result_on_equal;
  bool eq_range;

  uint errkey;				/* Last dup key */
  uint sortkey, key_used_on_scan;
  uint active_index;
  /* Length of ref (1-8 or the clustered key length) */
  uint ref_length;
  uint block_size;			/* index block size */
  uint raid_type,raid_chunks;
  FT_INFO *ft_handler;
  enum {NONE=0, INDEX, RND} inited;
  bool  auto_increment_column_changed;
  bool implicit_emptied;                /* Can be !=0 only if HEAP */
  const COND *pushed_cond;

  handler(const handlerton *ht_arg, TABLE *table_arg) :table(table_arg),
    ht(ht_arg),
    ref(0), 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),
    key_used_on_scan(MAX_KEY), active_index(MAX_KEY),
    ref_length(sizeof(my_off_t)), block_size(0),
    raid_type(0), ft_handler(0), inited(NONE), implicit_emptied(0),
    pushed_cond(NULL)
    {}
  virtual ~handler(void) { /* TODO: DBUG_ASSERT(inited == NONE); */ }
  virtual handler *clone(MEM_ROOT *mem_root);
  int ha_open(const char *name, int mode, int test_if_locked);
  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);
  void change_table_ptr(TABLE *table_arg) { table=table_arg; }
  virtual double scan_time()
    { return ulonglong2double(data_file_length) / IO_SIZE + 2; }
  virtual double read_time(uint index, uint ranges, ha_rows rows)
 { return rows2double(ranges+rows); }
  virtual const key_map *keys_to_use_for_scanning() { return &key_map_empty; }
  virtual bool has_transactions(){ return 0;}
  virtual uint extra_rec_buf_length() { return 0; }

  /*
    Return upper bound of current number of records in the table
    (max. of how many records one will retrieve when doing a full table scan)
    If upper bound is not known, HA_POS_ERROR should be returned as a max
    possible upper bound.
  */
  virtual ha_rows estimate_rows_upper_bound()
  { return records+EXTRA_RECORDS; }

  /*
    Get the row type from the storage engine.  If this method returns
    ROW_TYPE_NOT_USED, the information in HA_CREATE_INFO should be used.
  */
  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 "";}

  int ha_index_init(uint idx)
  {
    DBUG_ENTER("ha_index_init");
    DBUG_ASSERT(inited==NONE);
    inited=INDEX;
    DBUG_RETURN(index_init(idx));
  }
  int ha_index_end()
  {
    DBUG_ENTER("ha_index_end");
    DBUG_ASSERT(inited==INDEX);
    inited=NONE;
    DBUG_RETURN(index_end());
  }
  int ha_rnd_init(bool scan)
  {
    DBUG_ENTER("ha_rnd_init");
    DBUG_ASSERT(inited==NONE || (inited==RND && scan));
    inited=RND;
    DBUG_RETURN(rnd_init(scan));
  }
  int ha_rnd_end()
  {
    DBUG_ENTER("ha_rnd_end");
    DBUG_ASSERT(inited==RND);
    inited=NONE;
    DBUG_RETURN(rnd_end());
  }
  /* 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;
  }
  uint get_index(void) const { return active_index; }
  virtual int open(const char *name, int mode, uint test_if_locked)=0;
  virtual int close(void)=0;
  virtual int write_row(byte * buf) { return  HA_ERR_WRONG_COMMAND; }
  virtual int update_row(const byte * old_data, byte * new_data)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int delete_row(const byte * buf)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_read(byte * buf, const byte * key,
			 uint key_len, enum ha_rkey_function find_flag)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_read_idx(byte * buf, uint index, const byte * key,
			     uint key_len, enum ha_rkey_function find_flag);
  virtual int index_next(byte * buf)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_prev(byte * buf)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_first(byte * buf)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_last(byte * buf)
   { return  HA_ERR_WRONG_COMMAND; }
  virtual int index_next_same(byte *buf, const byte *key, uint keylen);
  virtual int index_read_last(byte * buf, const byte * key, uint key_len)
   { return (my_errno=HA_ERR_WRONG_COMMAND); }
  virtual int read_multi_range_first(KEY_MULTI_RANGE **found_range_p,
                                     KEY_MULTI_RANGE *ranges, uint range_count,
                                     bool sorted, HANDLER_BUFFER *buffer);
  virtual int read_multi_range_next(KEY_MULTI_RANGE **found_range_p);
  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();
  int compare_key(key_range *range);
  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(byte *buf) { return HA_ERR_WRONG_COMMAND; }
  virtual int rnd_next(byte *buf)=0;
  virtual int rnd_pos(byte * buf, byte *pos)=0;
  virtual int read_first_row(byte *buf, uint primary_key);
  /*
    The following function is only needed for tables that may be temporary
    tables during joins
  */
  virtual int restart_rnd_next(byte *buf, byte *pos)
    { return HA_ERR_WRONG_COMMAND; }
  virtual int rnd_same(byte *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; }
  virtual void position(const byte *record)=0;
  virtual int info(uint)=0; // see my_base.h for full description
  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 int reset() { return extra(HA_EXTRA_RESET); }
  virtual int external_lock(THD *thd, int lock_type) { return 0; }
  virtual void unlock_row() {}
  virtual int start_stmt(THD *thd, thr_lock_type lock_type) {return 0;}
  /*
    This is called to delete all rows in a table
    If the handler don't support this, then this function will
    return HA_ERR_WRONG_COMMAND and MySQL will delete the rows one
    by one.
  */
  virtual int delete_all_rows()
  { return (my_errno=HA_ERR_WRONG_COMMAND); }
  virtual ulonglong get_auto_increment();
  virtual void restore_auto_increment();

  /*
    Reset the auto-increment counter to the given value, i.e. the next row
    inserted will get the given value. This is called e.g. after TRUNCATE
    is emulated by doing a 'DELETE FROM t'. HA_ERR_WRONG_COMMAND is
    returned by storage engines that don't support this operation.
  */
  virtual int reset_auto_increment(ulonglong value)
  { return HA_ERR_WRONG_COMMAND; }

  virtual void update_create_info(HA_CREATE_INFO *create_info) {}
protected:
  /* to be implemented in handlers */

  /* admin commands - called from mysql_admin_table */
  virtual int check(THD* thd, HA_CHECK_OPT* check_opt)
  { return HA_ADMIN_NOT_IMPLEMENTED; }

  /*
     in these two methods check_opt can be modified
     to specify CHECK option to use to call check()
     upon the table
  */
  virtual int check_for_upgrade(HA_CHECK_OPT *check_opt)
  { return 0; }
public:
  int ha_check_for_upgrade(HA_CHECK_OPT *check_opt);
  int check_old_types();
  /* to be actually called to get 'check()' functionality*/
  int ha_check(THD *thd, HA_CHECK_OPT *check_opt);

  virtual int backup(THD* thd, HA_CHECK_OPT* check_opt)
  { return HA_ADMIN_NOT_IMPLEMENTED; }
  /*
    restore assumes .frm file must exist, and that generate_table() has been
    called; It will just copy the data file and run repair.
  */
  virtual int restore(THD* thd, HA_CHECK_OPT* check_opt)
  { return HA_ADMIN_NOT_IMPLEMENTED; }
protected:
  virtual int repair(THD* thd, HA_CHECK_OPT* check_opt)
  { return HA_ADMIN_NOT_IMPLEMENTED; }
public:
  int ha_repair(THD* thd, HA_CHECK_OPT* check_opt);
  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 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 bool check_and_repair(THD *thd) { return HA_ERR_WRONG_COMMAND; }
  virtual int dump(THD* thd, int fd = -1) { return HA_ERR_WRONG_COMMAND; }
  virtual int disable_indexes(uint mode) { return HA_ERR_WRONG_COMMAND; }
  virtual int enable_indexes(uint mode) { return HA_ERR_WRONG_COMMAND; }
  virtual int indexes_are_disabled(void) {return 0;}
  virtual void start_bulk_insert(ha_rows rows) {}
  virtual int end_bulk_insert() {return 0; }
  virtual int discard_or_import_tablespace(my_bool discard)
  {return HA_ERR_WRONG_COMMAND;}
  virtual int net_read_dump(NET* net) { return HA_ERR_WRONG_COMMAND; }
  virtual char *update_table_comment(const char * comment)
  { return (char*) comment;}
  virtual void append_create_info(String *packet) {}
  virtual char* get_foreign_key_create_info()
  { return(NULL);}  /* gets foreign key create string from InnoDB */
  /* used in ALTER TABLE; 1 if changing storage engine is allowed */
  virtual bool can_switch_engines() { return 1; }
  /* used in REPLACE; is > 0 if table is referred by a FOREIGN KEY */
  virtual int get_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) {}
  /* The following can be called without an open handler */
  virtual const char *table_type() const =0;
  virtual const char **bas_ext() const =0;
  virtual ulong table_flags(void) const =0;
  virtual ulong index_flags(uint idx, uint part, bool all_parts) const =0;
  virtual ulong index_ddl_flags(KEY *wanted_index) const
  { return (HA_DDL_SUPPORT); }
  virtual int add_index(TABLE *table_arg, KEY *key_info, uint num_of_keys)
  { return (HA_ERR_WRONG_COMMAND); }
  virtual int drop_index(TABLE *table_arg, uint *key_num, uint num_of_keys)
  { return (HA_ERR_WRONG_COMMAND); }

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

  /*
    default rename_table() and delete_table() rename/delete files with a
    given name and extensions from bas_ext()
  */
  virtual int rename_table(const char *from, const char *to);
  virtual int delete_table(const char *name);

  virtual int create(const char *name, TABLE *form, HA_CREATE_INFO *info)=0;

  /* lock_count() can be more than one if the table is a MERGE */
  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;

  /* Type of table for caching query */
  virtual uint8 table_cache_type() { return HA_CACHE_TBL_NONTRANSACT; }
  /* ask handler about permission to cache table when query is to be cached */
  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 1;
  }
 /*
  RETURN
    true  Primary key (if there is one) is clustered key covering all fields
    false otherwise
 */
 virtual bool primary_key_is_clustered() { return FALSE; }

 virtual int cmp_ref(const byte *ref1, const byte *ref2)
 {
   return memcmp(ref1, ref2, ref_length);
 }

 /*
   Condition pushdown to storage engines
 */

 /*
   Push condition down to the table handler.
   SYNOPSIS
     cond_push()
     cond   Condition to be pushed. The condition tree must not be
     modified by the by the caller.
   RETURN
     The 'remainder' condition that caller must use to filter out records.
     NULL means the handler will not return rows that do not match the
     passed condition.
   NOTES
   The pushed conditions form a stack (from which one can remove the
   last pushed condition using cond_pop).
   The table handler filters out rows using (pushed_cond1 AND pushed_cond2
   AND ... AND pushed_condN)
   or less restrictive condition, depending on handler's capabilities.

   handler->extra(HA_EXTRA_RESET) call empties the condition stack.
   Calls to rnd_init/rnd_end, index_init/index_end etc do not affect the
   condition stack.
 */
 virtual const COND *cond_push(const COND *cond) { return cond; };
 /*
   Pop the top condition from the condition stack of the handler instance.
   SYNOPSIS
     cond_pop()
     Pops the top if condition stack, if stack is not empty
 */
 virtual void cond_pop() { return; };
};

	/* Some extern variables used with handlers */

extern handlerton *sys_table_types[];
extern const char *ha_row_type[];
extern TYPELIB tx_isolation_typelib;
extern TYPELIB myisam_stats_method_typelib;
extern ulong total_ha, total_ha_2pc;

	/* Wrapper functions */
#define ha_commit_stmt(thd) (ha_commit_trans((thd), FALSE))
#define ha_rollback_stmt(thd) (ha_rollback_trans((thd), FALSE))
#define ha_commit(thd) (ha_commit_trans((thd), TRUE))
#define ha_rollback(thd) (ha_rollback_trans((thd), TRUE))

/* lookups */
enum db_type ha_resolve_by_name(const char *name, uint namelen);
const char *ha_get_storage_engine(enum db_type db_type);
handler *get_new_handler(TABLE *table, MEM_ROOT *alloc, enum db_type db_type);
enum db_type ha_checktype(THD *thd, enum db_type database_type,
                          bool no_substitute, bool report_error);
bool ha_check_storage_engine_flag(enum db_type db_type, uint32 flag);

/* basic stuff */
int ha_init(void);
TYPELIB *ha_known_exts(void);
int ha_panic(enum ha_panic_function flag);
int ha_update_statistics();
void ha_close_connection(THD* thd);
my_bool ha_storage_engine_is_enabled(enum db_type database_type);
bool ha_flush_logs(void);
void ha_drop_database(char* path);
int ha_create_table(const char *name, HA_CREATE_INFO *create_info,
		    bool update_create_info);
int ha_delete_table(THD *thd, enum db_type db_type, const char *path,
                    const char *alias, bool generate_warning);

/* discovery */
int ha_create_table_from_engine(THD* thd, const char *db, const char *name);
int ha_discover(THD* thd, const char* dbname, const char* name,
                const void** frmblob, uint* frmlen);
int ha_find_files(THD *thd,const char *db,const char *path,
                  const char *wild, bool dir,List<char>* files);
int ha_table_exists_in_engine(THD* thd, const char* db, const char* name);

/* key cache */
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);
int ha_end_key_cache(KEY_CACHE *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(XID *xid, bool commit);
int ha_commit_one_phase(THD *thd, bool all);
int ha_rollback_trans(THD *thd, bool all);
int ha_prepare(THD *thd);
int ha_recover(HASH *commit_list);

/* transactions: these functions never call handlerton functions directly */
int ha_commit_trans(THD *thd, bool all);
int ha_autocommit_or_rollback(THD *thd, int error);
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);

/* 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))