table_events_waits.cc

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/* Copyright (c) 2008, 2011, Oracle and/or its affiliates. All rights reserved.

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

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

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software Foundation,
  51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA */

#include "my_global.h"
#include "my_pthread.h"
#include "table_events_waits.h"
#include "pfs_global.h"
#include "pfs_instr_class.h"
#include "pfs_instr.h"
#include "pfs_events_waits.h"
#include "pfs_timer.h"
#include "m_string.h"

THR_LOCK table_events_waits_current::m_table_lock;

static const TABLE_FIELD_TYPE field_types[]=
{
  {
    { C_STRING_WITH_LEN("THREAD_ID") },
    { C_STRING_WITH_LEN("bigint(20)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("EVENT_ID") },
    { C_STRING_WITH_LEN("bigint(20)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("END_EVENT_ID") },
    { C_STRING_WITH_LEN("bigint(20)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("EVENT_NAME") },
    { C_STRING_WITH_LEN("varchar(128)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("SOURCE") },
    { C_STRING_WITH_LEN("varchar(64)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("TIMER_START") },
    { C_STRING_WITH_LEN("bigint(20)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("TIMER_END") },
    { C_STRING_WITH_LEN("bigint(20)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("TIMER_WAIT") },
    { C_STRING_WITH_LEN("bigint(20)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("SPINS") },
    { C_STRING_WITH_LEN("int(10)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("OBJECT_SCHEMA") },
    { C_STRING_WITH_LEN("varchar(64)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("OBJECT_NAME") },
    { C_STRING_WITH_LEN("varchar(512)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("INDEX_NAME") },
    { C_STRING_WITH_LEN("varchar(64)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("OBJECT_TYPE") },
    { C_STRING_WITH_LEN("varchar(64)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("OBJECT_INSTANCE_BEGIN") },
    { C_STRING_WITH_LEN("bigint(20)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("NESTING_EVENT_ID") },
    { C_STRING_WITH_LEN("bigint(20)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("NESTING_EVENT_TYPE") },
    { C_STRING_WITH_LEN("enum(\'STATEMENT\',\'STAGE\',\'WAIT\'") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("OPERATION") },
    { C_STRING_WITH_LEN("varchar(32)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("NUMBER_OF_BYTES") },
    { C_STRING_WITH_LEN("bigint(20)") },
    { NULL, 0}
  },
  {
    { C_STRING_WITH_LEN("FLAGS") },
    { C_STRING_WITH_LEN("int(10)") },
    { NULL, 0}
  }
};

TABLE_FIELD_DEF
table_events_waits_current::m_field_def=
{ 19, field_types };

PFS_engine_table_share
table_events_waits_current::m_share=
{
  { C_STRING_WITH_LEN("events_waits_current") },
  &pfs_truncatable_acl,
  &table_events_waits_current::create,
  NULL, /* write_row */
  &table_events_waits_current::delete_all_rows,
  NULL, /* get_row_count */
  1000, /* records */
  sizeof(pos_events_waits_current), /* ref length */
  &m_table_lock,
  &m_field_def,
  false /* checked */
};

THR_LOCK table_events_waits_history::m_table_lock;

PFS_engine_table_share
table_events_waits_history::m_share=
{
  { C_STRING_WITH_LEN("events_waits_history") },
  &pfs_truncatable_acl,
  &table_events_waits_history::create,
  NULL, /* write_row */
  &table_events_waits_history::delete_all_rows,
  NULL, /* get_row_count */
  1000, /* records */
  sizeof(pos_events_waits_history), /* ref length */
  &m_table_lock,
  &table_events_waits_current::m_field_def,
  false /* checked */
};

THR_LOCK table_events_waits_history_long::m_table_lock;

PFS_engine_table_share
table_events_waits_history_long::m_share=
{
  { C_STRING_WITH_LEN("events_waits_history_long") },
  &pfs_truncatable_acl,
  &table_events_waits_history_long::create,
  NULL, /* write_row */
  &table_events_waits_history_long::delete_all_rows,
  NULL, /* get_row_count */
  10000, /* records */
  sizeof(PFS_simple_index), /* ref length */
  &m_table_lock,
  &table_events_waits_current::m_field_def,
  false /* checked */
};

table_events_waits_common::table_events_waits_common
(const PFS_engine_table_share *share, void *pos)
  : PFS_engine_table(share, pos),
  m_row_exists(false)
{}

void table_events_waits_common::clear_object_columns()
{
  m_row.m_object_type= NULL;
  m_row.m_object_type_length= 0;
  m_row.m_object_schema_length= 0;
  m_row.m_object_name_length= 0;
  m_row.m_index_name_length= 0;
  m_row.m_object_instance_addr= 0;
}

int table_events_waits_common::make_table_object_columns(volatile PFS_events_waits *wait)
{
  uint safe_index;
  PFS_table_share *safe_table_share;

  safe_table_share= sanitize_table_share(wait->m_weak_table_share);
  if (unlikely(safe_table_share == NULL))
    return 1;

  if (wait->m_object_type == OBJECT_TYPE_TABLE)
  {
    m_row.m_object_type= "TABLE";
    m_row.m_object_type_length= 5;
  }
  else
  {
    m_row.m_object_type= "TEMPORARY TABLE";
    m_row.m_object_type_length= 15;
  }

  if (safe_table_share->get_version() == wait->m_weak_version)
  {
    /* OBJECT SCHEMA */
    m_row.m_object_schema_length= safe_table_share->m_schema_name_length;
    if (unlikely((m_row.m_object_schema_length == 0) ||
                 (m_row.m_object_schema_length > sizeof(m_row.m_object_schema))))
      return 1;
    memcpy(m_row.m_object_schema, safe_table_share->m_schema_name, m_row.m_object_schema_length);

    /* OBJECT NAME */
    m_row.m_object_name_length= safe_table_share->m_table_name_length;
    if (unlikely((m_row.m_object_name_length == 0) ||
                 (m_row.m_object_name_length > sizeof(m_row.m_object_name))))
      return 1;
    memcpy(m_row.m_object_name, safe_table_share->m_table_name, m_row.m_object_name_length);

    /* INDEX NAME */
    safe_index= wait->m_index;
    uint safe_key_count= sanitize_index_count(safe_table_share->m_key_count);
    if (safe_index < safe_key_count)
    {
      PFS_table_key *key= & safe_table_share->m_keys[safe_index];
      m_row.m_index_name_length= key->m_name_length;
      if (unlikely((m_row.m_index_name_length == 0) ||
                   (m_row.m_index_name_length > sizeof(m_row.m_index_name))))
        return 1;
      memcpy(m_row.m_index_name, key->m_name, m_row.m_index_name_length);
    }
    else
      m_row.m_index_name_length= 0;
  }
  else
  {
    m_row.m_object_schema_length= 0;
    m_row.m_object_name_length= 0;
    m_row.m_index_name_length= 0;
  }

  m_row.m_object_instance_addr= (intptr) wait->m_object_instance_addr;
  return 0;
}

int table_events_waits_common::make_file_object_columns(volatile PFS_events_waits *wait)
{
  PFS_file *safe_file;

  safe_file= sanitize_file(wait->m_weak_file);
  if (unlikely(safe_file == NULL))
    return 1;

  m_row.m_object_type= "FILE";
  m_row.m_object_type_length= 4;
  m_row.m_object_schema_length= 0;
  m_row.m_object_instance_addr= (intptr) wait->m_object_instance_addr;

  if (safe_file->get_version() == wait->m_weak_version)
  {
    /* OBJECT NAME */
    m_row.m_object_name_length= safe_file->m_filename_length;
    if (unlikely((m_row.m_object_name_length == 0) ||
                 (m_row.m_object_name_length > sizeof(m_row.m_object_name))))
      return 1;
    memcpy(m_row.m_object_name, safe_file->m_filename, m_row.m_object_name_length);
  }
  else
  {
    m_row.m_object_name_length= 0;
  }

  m_row.m_index_name_length= 0;

  return 0;
}

int table_events_waits_common::make_socket_object_columns(volatile PFS_events_waits *wait)
{
  PFS_socket *safe_socket;

  safe_socket= sanitize_socket(wait->m_weak_socket);
  if (unlikely(safe_socket == NULL))
    return 1;

  m_row.m_object_type= "SOCKET";
  m_row.m_object_type_length= 6;
  m_row.m_object_schema_length= 0;
  m_row.m_object_instance_addr= (intptr) wait->m_object_instance_addr;

  if (safe_socket->get_version() == wait->m_weak_version)
  {
    /* Convert port number to string, include delimiter in port name length */

    uint port;
    char port_str[128];
    char ip_str[INET6_ADDRSTRLEN+1];
    uint ip_len= 0;
    port_str[0]= ':';

    /* Get the IP address and port number */
    ip_len= pfs_get_socket_address(ip_str, sizeof(ip_str), &port,
                                   &safe_socket->m_sock_addr,
                                   safe_socket->m_addr_len);

    /* Convert port number to a string (length includes ':') */
    int port_len= int10_to_str(port, (port_str+1), 10) - port_str + 1;

    /* OBJECT NAME */
    m_row.m_object_name_length= ip_len + port_len;

    if (unlikely((m_row.m_object_name_length == 0) ||
                 (m_row.m_object_name_length > sizeof(m_row.m_object_name))))
      return 1;

    char *name= m_row.m_object_name;
    memcpy(name, ip_str, ip_len);
    memcpy(name + ip_len, port_str, port_len);
  }
  else
  {
    m_row.m_object_name_length= 0;
  }

  m_row.m_index_name_length= 0;

  return 0;
}

void table_events_waits_common::make_row(bool thread_own_wait,
                                         PFS_thread *pfs_thread,
                                         volatile PFS_events_waits *wait)
{
  pfs_lock lock;
  PFS_thread *safe_thread;
  PFS_instr_class *safe_class;
  const char *base;
  const char *safe_source_file;

  m_row_exists= false;
  safe_thread= sanitize_thread(pfs_thread);
  if (unlikely(safe_thread == NULL))
    return;

  /* Protect this reader against a thread termination */
  if (thread_own_wait)
    safe_thread->m_lock.begin_optimistic_lock(&lock);

  /*
    Design choice:
    We could have used a pfs_lock in PFS_events_waits here,
    to protect the reader from concurrent event generation,
    but this leads to too many pfs_lock atomic operations
    each time an event is recorded:
    - 1 dirty() + 1 allocated() per event start, for EVENTS_WAITS_CURRENT
    - 1 dirty() + 1 allocated() per event end, for EVENTS_WAITS_CURRENT
    - 1 dirty() + 1 allocated() per copy to EVENTS_WAITS_HISTORY
    - 1 dirty() + 1 allocated() per copy to EVENTS_WAITS_HISTORY_LONG
    or 8 atomics per recorded event.
    The problem is that we record a *lot* of events ...

    This code is prepared to accept *dirty* records,
    and sanitizes all the data before returning a row.
  */

  /*
    PFS_events_waits::m_class needs to be sanitized,
    for race conditions when this code:
    - reads a new value in m_wait_class,
    - reads an old value in m_class.
  */
  switch (wait->m_wait_class)
  {
  case WAIT_CLASS_IDLE:
    clear_object_columns();
    safe_class= sanitize_idle_class(wait->m_class);
    break;
  case WAIT_CLASS_MUTEX:
    clear_object_columns();
    safe_class= sanitize_mutex_class((PFS_mutex_class*) wait->m_class);
    break;
  case WAIT_CLASS_RWLOCK:
    clear_object_columns();
    safe_class= sanitize_rwlock_class((PFS_rwlock_class*) wait->m_class);
    break;
  case WAIT_CLASS_COND:
    clear_object_columns();
    safe_class= sanitize_cond_class((PFS_cond_class*) wait->m_class);
    break;
  case WAIT_CLASS_TABLE:
    if (make_table_object_columns(wait))
      return;
    safe_class= sanitize_table_class(wait->m_class);
    break;
  case WAIT_CLASS_FILE:
    if (make_file_object_columns(wait))
      return;
    safe_class= sanitize_file_class((PFS_file_class*) wait->m_class);
    break;
  case WAIT_CLASS_SOCKET:
    if (make_socket_object_columns(wait))
      return;
    safe_class= sanitize_socket_class((PFS_socket_class*) wait->m_class);
    break;
  case NO_WAIT_CLASS:
  default:
    return;
  }

  if (unlikely(safe_class == NULL))
    return;

  m_row.m_thread_internal_id= safe_thread->m_thread_internal_id;
  m_row.m_event_id= wait->m_event_id;
  m_row.m_end_event_id= wait->m_end_event_id;
  m_row.m_nesting_event_id= wait->m_nesting_event_id;
  m_row.m_nesting_event_type= wait->m_nesting_event_type;

  get_normalizer(safe_class);
  m_normalizer->to_pico(wait->m_timer_start, wait->m_timer_end,
                      & m_row.m_timer_start, & m_row.m_timer_end, & m_row.m_timer_wait);

  m_row.m_name= safe_class->m_name;
  m_row.m_name_length= safe_class->m_name_length;

  /*
    We are assuming this pointer is sane,
    since it comes from __FILE__.
  */
  safe_source_file= wait->m_source_file;
  if (unlikely(safe_source_file == NULL))
    return;

  base= base_name(wait->m_source_file);
  m_row.m_source_length= my_snprintf(m_row.m_source, sizeof(m_row.m_source),
                                     "%s:%d", base, wait->m_source_line);
  if (m_row.m_source_length > sizeof(m_row.m_source))
    m_row.m_source_length= sizeof(m_row.m_source);
  m_row.m_operation= wait->m_operation;
  m_row.m_number_of_bytes= wait->m_number_of_bytes;
  m_row.m_flags= wait->m_flags;

  if (thread_own_wait)
  {
    if (safe_thread->m_lock.end_optimistic_lock(&lock))
      m_row_exists= true;
  }
  else
  {
    /*
      For EVENTS_WAITS_HISTORY_LONG (thread_own_wait is false),
      the wait record is always valid, because it is not stored
      in memory owned by pfs_thread.
      Even when the thread terminated, the record is mostly readable,
      so this record is displayed.
    */
    m_row_exists= true;
  }
}

static const LEX_STRING operation_names_map[]=
{
  /* Mutex operations */
  { C_STRING_WITH_LEN("lock") },
  { C_STRING_WITH_LEN("try_lock") },

  /* RWLock operations */
  { C_STRING_WITH_LEN("read_lock") },
  { C_STRING_WITH_LEN("write_lock") },
  { C_STRING_WITH_LEN("try_read_lock") },
  { C_STRING_WITH_LEN("try_write_lock") },

  /* Condition operations */
  { C_STRING_WITH_LEN("wait") },
  { C_STRING_WITH_LEN("timed_wait") },

  /* File operations */
  { C_STRING_WITH_LEN("create") },
  { C_STRING_WITH_LEN("create") }, /* create tmp */
  { C_STRING_WITH_LEN("open") },
  { C_STRING_WITH_LEN("open") }, /* stream open */
  { C_STRING_WITH_LEN("close") },
  { C_STRING_WITH_LEN("close") }, /* stream close */
  { C_STRING_WITH_LEN("read") },
  { C_STRING_WITH_LEN("write") },
  { C_STRING_WITH_LEN("seek") },
  { C_STRING_WITH_LEN("tell") },
  { C_STRING_WITH_LEN("flush") },
  { C_STRING_WITH_LEN("stat") },
  { C_STRING_WITH_LEN("stat") }, /* fstat */
  { C_STRING_WITH_LEN("chsize") },
  { C_STRING_WITH_LEN("delete") },
  { C_STRING_WITH_LEN("rename") },
  { C_STRING_WITH_LEN("sync") },

  /* Table io operations */
  { C_STRING_WITH_LEN("fetch") },
  { C_STRING_WITH_LEN("insert") }, /* write row */
  { C_STRING_WITH_LEN("update") }, /* update row */
  { C_STRING_WITH_LEN("delete") }, /* delete row */

  /* Table lock operations */
  { C_STRING_WITH_LEN("read normal") },
  { C_STRING_WITH_LEN("read with shared locks") },
  { C_STRING_WITH_LEN("read high priority") },
  { C_STRING_WITH_LEN("read no inserts") },
  { C_STRING_WITH_LEN("write allow write") },
  { C_STRING_WITH_LEN("write concurrent insert") },
  { C_STRING_WITH_LEN("write delayed") },
  { C_STRING_WITH_LEN("write low priority") },
  { C_STRING_WITH_LEN("write normal") },
  { C_STRING_WITH_LEN("read external") },
  { C_STRING_WITH_LEN("write external") },

  /* Socket operations */
  { C_STRING_WITH_LEN("create") },
  { C_STRING_WITH_LEN("connect") },
  { C_STRING_WITH_LEN("bind") },
  { C_STRING_WITH_LEN("close") },
  { C_STRING_WITH_LEN("send") },
  { C_STRING_WITH_LEN("recv") },
  { C_STRING_WITH_LEN("sendto") },
  { C_STRING_WITH_LEN("recvfrom") },
  { C_STRING_WITH_LEN("sendmsg") },
  { C_STRING_WITH_LEN("recvmsg") },
  { C_STRING_WITH_LEN("seek") },
  { C_STRING_WITH_LEN("opt") },
  { C_STRING_WITH_LEN("stat") },
  { C_STRING_WITH_LEN("shutdown") },
  { C_STRING_WITH_LEN("select") },

  /* Idle operations */
  { C_STRING_WITH_LEN("idle") }
};


int table_events_waits_common::read_row_values(TABLE *table,
                                               unsigned char *buf,
                                               Field **fields,
                                               bool read_all)
{
  Field *f;
  const LEX_STRING *operation;

  compile_time_assert(COUNT_OPERATION_TYPE ==
                      array_elements(operation_names_map));

  if (unlikely(! m_row_exists))
    return HA_ERR_RECORD_DELETED;

  /* Set the null bits */
  DBUG_ASSERT(table->s->null_bytes == 2);
  buf[0]= 0;
  buf[1]= 0;

  /*
    Some columns are unreliable, because they are joined with other buffers,
    which could have changed and been reused for something else.
    These columns are:
    - THREAD_ID (m_thread joins with PFS_thread),
    - SCHEMA_NAME (m_schema_name joins with PFS_table_share)
    - OBJECT_NAME (m_object_name joins with PFS_table_share)
  */
  for (; (f= *fields) ; fields++)
  {
    if (read_all || bitmap_is_set(table->read_set, f->field_index))
    {
      switch(f->field_index)
      {
      case 0: /* THREAD_ID */
        set_field_ulonglong(f, m_row.m_thread_internal_id);
        break;
      case 1: /* EVENT_ID */
        set_field_ulonglong(f, m_row.m_event_id);
        break;
      case 2: /* END_EVENT_ID */
        if (m_row.m_end_event_id > 0)
          set_field_ulonglong(f, m_row.m_end_event_id - 1);
        else
          f->set_null();
        break;
      case 3: /* EVENT_NAME */
        set_field_varchar_utf8(f, m_row.m_name, m_row.m_name_length);
        break;
      case 4: /* SOURCE */
        set_field_varchar_utf8(f, m_row.m_source, m_row.m_source_length);
        break;
      case 5: /* TIMER_START */
        if (m_row.m_timer_start != 0)
          set_field_ulonglong(f, m_row.m_timer_start);
        else
          f->set_null();
        break;
      case 6: /* TIMER_END */
        if (m_row.m_timer_end != 0)
          set_field_ulonglong(f, m_row.m_timer_end);
        else
          f->set_null();
        break;
      case 7: /* TIMER_WAIT */
        if (m_row.m_timer_wait != 0)
          set_field_ulonglong(f, m_row.m_timer_wait);
        else
          f->set_null();
        break;
      case 8: /* SPINS */
        f->set_null();
        break;
      case 9: /* OBJECT_SCHEMA */
        if (m_row.m_object_schema_length > 0)
        {
          set_field_varchar_utf8(f, m_row.m_object_schema,
                                 m_row.m_object_schema_length);
        }
        else
          f->set_null();
        break;
      case 10: /* OBJECT_NAME */
        if (m_row.m_object_name_length > 0)
        {
          set_field_varchar_utf8(f, m_row.m_object_name,
                                 m_row.m_object_name_length);
        }
        else
          f->set_null();
        break;
      case 11: /* INDEX_NAME */
        if (m_row.m_index_name_length > 0)
        {
          set_field_varchar_utf8(f, m_row.m_index_name,
                                 m_row.m_index_name_length);
        }
        else
          f->set_null();
        break;
      case 12: /* OBJECT_TYPE */
        if (m_row.m_object_type)
        {
          set_field_varchar_utf8(f, m_row.m_object_type,
                                 m_row.m_object_type_length);
        }
        else
          f->set_null();
        break;
      case 13: /* OBJECT_INSTANCE */
        set_field_ulonglong(f, m_row.m_object_instance_addr);
        break;
      case 14: /* NESTING_EVENT_ID */
        if (m_row.m_nesting_event_id != 0)
          set_field_ulonglong(f, m_row.m_nesting_event_id);
        else
          f->set_null();
        break;
      case 15: /* NESTING_EVENT_TYPE */
        if (m_row.m_nesting_event_id != 0)
          set_field_enum(f, m_row.m_nesting_event_type);
        else
          f->set_null();
        break;
      case 16: /* OPERATION */
        operation= &operation_names_map[(int) m_row.m_operation - 1];
        set_field_varchar_utf8(f, operation->str, operation->length);
        break;
      case 17: /* NUMBER_OF_BYTES */
        if ((m_row.m_operation == OPERATION_TYPE_FILEREAD) ||
            (m_row.m_operation == OPERATION_TYPE_FILEWRITE) ||
            (m_row.m_operation == OPERATION_TYPE_FILECHSIZE) ||
            (m_row.m_operation == OPERATION_TYPE_SOCKETSEND) ||
            (m_row.m_operation == OPERATION_TYPE_SOCKETRECV) ||
            (m_row.m_operation == OPERATION_TYPE_SOCKETSENDTO) ||
            (m_row.m_operation == OPERATION_TYPE_SOCKETRECVFROM))
          set_field_ulonglong(f, m_row.m_number_of_bytes);
        else
          f->set_null();
        break;
      case 18: /* FLAGS */
        f->set_null();
        break;
      default:
        DBUG_ASSERT(false);
      }
    }
  }
  return 0;
}

PFS_engine_table* table_events_waits_current::create(void)
{
  return new table_events_waits_current();
}

table_events_waits_current::table_events_waits_current()
  : table_events_waits_common(&m_share, &m_pos),
  m_pos(), m_next_pos()
{}

void table_events_waits_current::reset_position(void)
{
  m_pos.reset();
  m_next_pos.reset();
}

int table_events_waits_current::rnd_next(void)
{
  PFS_thread *pfs_thread;
  PFS_events_waits *wait;

  for (m_pos.set_at(&m_next_pos);
       m_pos.m_index_1 < thread_max;
       m_pos.next_thread())
  {
    pfs_thread= &thread_array[m_pos.m_index_1];

    if (! pfs_thread->m_lock.is_populated())
    {
      /* This thread does not exist */
      continue;
    }

    /*
      We do not show nested events for now,
      this will be revised with TABLE io
    */
// #define ONLY_SHOW_ONE_WAIT

#ifdef ONLY_SHOW_ONE_WAIT
    if (m_pos.m_index_2 >= 1)
      continue;
#else
    /* m_events_waits_stack[0] is a dummy record */
    PFS_events_waits *top_wait = &pfs_thread->m_events_waits_stack[WAIT_STACK_BOTTOM];
    wait= &pfs_thread->m_events_waits_stack[m_pos.m_index_2 + WAIT_STACK_BOTTOM];

    PFS_events_waits *safe_current = pfs_thread->m_events_waits_current;

    if (safe_current == top_wait)
    {
      /* Display the last top level wait, when completed */
      if (m_pos.m_index_2 >= 1)
        continue;
    }
    else
    {
      /* Display all pending waits, when in progress */
      if (wait >= safe_current)
        continue;
    }
#endif

    if (wait->m_wait_class == NO_WAIT_CLASS)
    {
      /*
        This locker does not exist.
        There can not be more lockers in the stack, skip to the next thread
      */
      continue;
    }

    make_row(true, pfs_thread, wait);
    /* Next iteration, look for the next locker in this thread */
    m_next_pos.set_after(&m_pos);
    return 0;
  }

  return HA_ERR_END_OF_FILE;
}

int table_events_waits_current::rnd_pos(const void *pos)
{
  PFS_thread *pfs_thread;
  PFS_events_waits *wait;

  set_position(pos);
  DBUG_ASSERT(m_pos.m_index_1 < thread_max);
  pfs_thread= &thread_array[m_pos.m_index_1];

  if (! pfs_thread->m_lock.is_populated())
    return HA_ERR_RECORD_DELETED;

#ifdef ONLY_SHOW_ONE_WAIT
  if (m_pos.m_index_2 >= 1)
    return HA_ERR_RECORD_DELETED;
#else
  /* m_events_waits_stack[0] is a dummy record */
  PFS_events_waits *top_wait = &pfs_thread->m_events_waits_stack[WAIT_STACK_BOTTOM];
  wait= &pfs_thread->m_events_waits_stack[m_pos.m_index_2 + WAIT_STACK_BOTTOM];

  PFS_events_waits *safe_current = pfs_thread->m_events_waits_current;

  if (safe_current == top_wait)
  {
    /* Display the last top level wait, when completed */
    if (m_pos.m_index_2 >= 1)
      return HA_ERR_RECORD_DELETED;
  }
  else
  {
    /* Display all pending waits, when in progress */
    if (wait >= safe_current)
      return HA_ERR_RECORD_DELETED;
  }
#endif

  DBUG_ASSERT(m_pos.m_index_2 < WAIT_STACK_LOGICAL_SIZE);

  if (wait->m_wait_class == NO_WAIT_CLASS)
    return HA_ERR_RECORD_DELETED;

  make_row(true, pfs_thread, wait);
  return 0;
}

int table_events_waits_current::delete_all_rows(void)
{
  reset_events_waits_current();
  return 0;
}

PFS_engine_table* table_events_waits_history::create(void)
{
  return new table_events_waits_history();
}

table_events_waits_history::table_events_waits_history()
  : table_events_waits_common(&m_share, &m_pos),
  m_pos(), m_next_pos()
{}

void table_events_waits_history::reset_position(void)
{
  m_pos.reset();
  m_next_pos.reset();
}

int table_events_waits_history::rnd_next(void)
{
  PFS_thread *pfs_thread;
  PFS_events_waits *wait;

  if (events_waits_history_per_thread == 0)
    return HA_ERR_END_OF_FILE;

  for (m_pos.set_at(&m_next_pos);
       m_pos.m_index_1 < thread_max;
       m_pos.next_thread())
  {
    pfs_thread= &thread_array[m_pos.m_index_1];

    if (! pfs_thread->m_lock.is_populated())
    {
      /* This thread does not exist */
      continue;
    }

    if (m_pos.m_index_2 >= events_waits_history_per_thread)
    {
      /* This thread does not have more (full) history */
      continue;
    }

    if ( ! pfs_thread->m_waits_history_full &&
        (m_pos.m_index_2 >= pfs_thread->m_waits_history_index))
    {
      /* This thread does not have more (not full) history */
      continue;
    }

    if (pfs_thread->m_waits_history[m_pos.m_index_2].m_wait_class
        == NO_WAIT_CLASS)
    {
      /*
        This locker does not exist.
        There can not be more lockers in the stack, skip to the next thread
      */
      continue;
    }

    wait= &pfs_thread->m_waits_history[m_pos.m_index_2];

    make_row(true, pfs_thread, wait);
    /* Next iteration, look for the next history in this thread */
    m_next_pos.set_after(&m_pos);
    return 0;
  }

  return HA_ERR_END_OF_FILE;
}

int table_events_waits_history::rnd_pos(const void *pos)
{
  PFS_thread *pfs_thread;
  PFS_events_waits *wait;

  DBUG_ASSERT(events_waits_history_per_thread != 0);
  set_position(pos);
  DBUG_ASSERT(m_pos.m_index_1 < thread_max);
  pfs_thread= &thread_array[m_pos.m_index_1];

  if (! pfs_thread->m_lock.is_populated())
    return HA_ERR_RECORD_DELETED;

  DBUG_ASSERT(m_pos.m_index_2 < events_waits_history_per_thread);

  if ( ! pfs_thread->m_waits_history_full &&
      (m_pos.m_index_2 >= pfs_thread->m_waits_history_index))
    return HA_ERR_RECORD_DELETED;

  wait= &pfs_thread->m_waits_history[m_pos.m_index_2];

  if (wait->m_wait_class == NO_WAIT_CLASS)
    return HA_ERR_RECORD_DELETED;

  make_row(true, pfs_thread, wait);
  return 0;
}

int table_events_waits_history::delete_all_rows(void)
{
  reset_events_waits_history();
  return 0;
}

PFS_engine_table* table_events_waits_history_long::create(void)
{
  return new table_events_waits_history_long();
}

table_events_waits_history_long::table_events_waits_history_long()
  : table_events_waits_common(&m_share, &m_pos),
  m_pos(0), m_next_pos(0)
{}

void table_events_waits_history_long::reset_position(void)
{
  m_pos.m_index= 0;
  m_next_pos.m_index= 0;
}

int table_events_waits_history_long::rnd_next(void)
{
  PFS_events_waits *wait;
  uint limit;

  if (events_waits_history_long_size == 0)
    return HA_ERR_END_OF_FILE;

  if (events_waits_history_long_full)
    limit= events_waits_history_long_size;
  else
    limit= events_waits_history_long_index % events_waits_history_long_size;

  for (m_pos.set_at(&m_next_pos); m_pos.m_index < limit; m_pos.next())
  {
    wait= &events_waits_history_long_array[m_pos.m_index];

    if (wait->m_wait_class != NO_WAIT_CLASS)
    {
      make_row(false, wait->m_thread, wait);
      /* Next iteration, look for the next entry */
      m_next_pos.set_after(&m_pos);
      return 0;
    }
  }

  return HA_ERR_END_OF_FILE;
}

int table_events_waits_history_long::rnd_pos(const void *pos)
{
  PFS_events_waits *wait;
  uint limit;

  if (events_waits_history_long_size == 0)
    return HA_ERR_RECORD_DELETED;

  set_position(pos);

  if (events_waits_history_long_full)
    limit= events_waits_history_long_size;
  else
    limit= events_waits_history_long_index % events_waits_history_long_size;

  if (m_pos.m_index >= limit)
    return HA_ERR_RECORD_DELETED;

  wait= &events_waits_history_long_array[m_pos.m_index];

  if (wait->m_wait_class == NO_WAIT_CLASS)
    return HA_ERR_RECORD_DELETED;

  make_row(false, wait->m_thread, wait);
  return 0;
}

int table_events_waits_history_long::delete_all_rows(void)
{
  reset_events_waits_history_long();
  return 0;
}