Adding upstream version 1:10.6.11.upstream/1%10.6.11upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1291 insertions, 0 deletions

diff --git a/storage/perfschema/pfs_variable.cc b/storage/perfschema/pfs_variable.cc
new file mode 100644
index 00000000..982409ba
--- /dev/null
+++ b/storage/perfschema/pfs_variable.cc
@@ -0,0 +1,1291 @@
+/* Copyright (c) 2015, 2022, Oracle and/or its affiliates.
+   Copyright (c) 2020, MariaDB Corporation.
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License, version 2.0,
+  as published by the Free Software Foundation.
+
+  This program is also distributed with certain software (including
+  but not limited to OpenSSL) that is licensed under separate terms,
+  as designated in a particular file or component or in included license
+  documentation.  The authors of MySQL hereby grant you an additional
+  permission to link the program and your derivative works with the
+  separately licensed software that they have included with MySQL.
+
+  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, version 2.0, for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */
+
+/**
+  @file storage/perfschema/pfs_variable.cc
+  Performance schema system variable and status variable (implementation).
+*/
+#include "sql_plugin.h"
+#include "pfs_variable.h"
+#include "my_sys.h"
+#include "debug_sync.h"
+#include "pfs.h"
+#include "pfs_global.h"
+#include "pfs_visitor.h"
+#include "sql_audit.h"                      // audit_global_variable_get
+
+static inline SHOW_SCOPE show_scope_from_type(enum enum_mysql_show_type type)
+{
+  switch(type) {
+    case SHOW_BOOL:
+    case SHOW_CHAR:
+    case SHOW_CHAR_PTR:
+    case SHOW_DOUBLE:
+    case SHOW_HAVE:
+    case SHOW_HA_ROWS:
+    case SHOW_KEY_CACHE_LONG:
+    case SHOW_LEX_STRING:
+    case SHOW_LONG_NOFLUSH:
+    case SHOW_MY_BOOL:
+    case SHOW_SINT:
+    case SHOW_SLONG:
+    case SHOW_SLONGLONG:
+    case SHOW_SYS:
+    case SHOW_UINT:
+    case SHOW_ULONG:
+    case SHOW_ULONGLONG:
+      return SHOW_SCOPE_GLOBAL;
+
+    case SHOW_DOUBLE_STATUS:
+    case SHOW_LONGLONG_STATUS:
+    case SHOW_LONG_STATUS:
+      return SHOW_SCOPE_ALL;
+
+    case SHOW_ARRAY:
+    case SHOW_FUNC:
+    case SHOW_SIMPLE_FUNC:
+    case SHOW_UNDEF:
+    default:
+      return SHOW_SCOPE_UNDEF;
+  }
+  return SHOW_SCOPE_UNDEF;
+}
+
+
+/**
+  CLASS PFS_system_variable_cache
+*/
+
+/**
+  Build a sorted list of all system variables from the system variable hash.
+  Filter by scope. Must be called inside of LOCK_plugin_delete.
+*/
+bool PFS_system_variable_cache::init_show_var_array(enum_var_type scope, bool strict)
+{
+  assert(!m_initialized);
+  m_query_scope= scope;
+
+  mysql_prlock_rdlock(&LOCK_system_variables_hash);
+  DEBUG_SYNC(m_current_thd, "acquired_LOCK_system_variables_hash");
+
+  /* Record the system variable hash version to detect subsequent changes. */
+  m_version= get_system_variable_hash_version();
+
+  /* Build the SHOW_VAR array from the system variable hash. */
+  SHOW_VAR *vars= enumerate_sys_vars(m_current_thd, true, m_query_scope/*, strict */);
+  m_show_var_array.reserve(get_system_variable_hash_records());
+  for (int i=0; vars[i].name; i++)
+    m_show_var_array.set(i, vars[i]);
+
+  mysql_prlock_unlock(&LOCK_system_variables_hash);
+
+  /* Increase cache size if necessary. */
+  m_cache.reserve(m_show_var_array.elements());
+
+  m_initialized= true;
+  return true;
+}
+
+/**
+  Build an array of SHOW_VARs from the system variable hash.
+  Filter for SESSION scope.
+*/
+bool PFS_system_variable_cache::do_initialize_session(void)
+{
+  /* Block plugins from unloading. */
+  mysql_mutex_lock(&LOCK_plugin_delete);
+
+  /* Build the array. */
+  bool ret= init_show_var_array(OPT_SESSION, true);
+
+  mysql_mutex_unlock(&LOCK_plugin_delete);
+  return ret;
+}
+
+/**
+  Match system variable scope to desired scope.
+*/
+bool PFS_system_variable_cache::match_scope(int scope)
+{
+  switch (scope)
+  {
+    case sys_var::GLOBAL:
+      return m_query_scope == OPT_GLOBAL;
+      break;
+
+    case sys_var::SESSION:
+      return (m_query_scope == OPT_GLOBAL || m_query_scope == OPT_SESSION);
+      break;
+
+    case sys_var::ONLY_SESSION:
+      return m_query_scope == OPT_SESSION;
+      break;
+
+    default:
+      return false;
+      break;
+  }
+  return false;
+}
+
+/**
+  Build a GLOBAL system variable cache.
+*/
+int PFS_system_variable_cache::do_materialize_global(void)
+{
+  /* Block system variable additions or deletions. */
+  mysql_mutex_lock(&LOCK_global_system_variables);
+
+  m_materialized= false;
+
+  /*
+     Build array of SHOW_VARs from system variable hash. Do this within
+     LOCK_plugin_delete to ensure that the hash table remains unchanged
+     during materialization.
+   */
+  if (!m_external_init)
+    init_show_var_array(OPT_GLOBAL, true);
+
+  /* Resolve the value for each SHOW_VAR in the array, add to cache. */
+  for (SHOW_VAR *show_var= m_show_var_array.front();
+       show_var->value && (show_var != m_show_var_array.end()); show_var++)
+  {
+    const char* name= show_var->name;
+    sys_var *value= (sys_var *)show_var->value;
+    assert(value);
+
+    if ((m_query_scope == OPT_GLOBAL) &&
+        (!my_strcasecmp(system_charset_info, name, "sql_log_bin")))
+    {
+      /*
+        PLEASE READ:
+        http://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-6.html
+
+        SQL_LOG_BIN is:
+        - declared in sys_vars.cc as both GLOBAL and SESSION in 5.7
+        - impossible to SET with SET GLOBAL (raises an error)
+        - and yet can be read with @@global.sql_log_bin
+
+        When show_compatibility_56 = ON,
+        - SHOW GLOBAL VARIABLES does expose a row for SQL_LOG_BIN
+        - INFORMATION_SCHEMA.GLOBAL_VARIABLES also does expose a row,
+        both are for backward compatibility of existing applications,
+        so that no application logic change is required.
+
+        Now, with show_compatibility_56 = OFF (aka, in this code)
+        - SHOW GLOBAL VARIABLES does -- not -- expose a row for SQL_LOG_BIN
+        - PERFORMANCE_SCHEMA.GLOBAL_VARIABLES also does -- not -- expose a row
+        so that a clean interface is exposed to (upgraded and modified) applications.
+
+        The assert below will fail once SQL_LOG_BIN really is defined
+        as SESSION_ONLY (in 5.8), so that this special case can be removed.
+      */
+      assert(value->scope() == sys_var::SESSION);
+      continue;
+    }
+
+    /* Match the system variable scope to the target scope. */
+    if (match_scope(value->scope()))
+    {
+      /* Resolve value, convert to text, add to cache. */
+      System_variable system_var(m_current_thd, show_var, m_query_scope, false);
+      m_cache.push(system_var);
+    }
+  }
+
+  m_materialized= true;
+  mysql_mutex_unlock(&LOCK_global_system_variables);
+  return 0;
+}
+
+/**
+  Build a GLOBAL and SESSION system variable cache.
+*/
+int PFS_system_variable_cache::do_materialize_all(THD *unsafe_thd)
+{
+  int ret= 1;
+
+  m_unsafe_thd= unsafe_thd;
+  m_safe_thd= NULL;
+  m_materialized= false;
+  m_cache.clear();
+
+  /* Block plugins from unloading. */
+  mysql_mutex_lock(&LOCK_plugin_delete);
+
+  /*
+     Build array of SHOW_VARs from system variable hash. Do this within
+     LOCK_plugin_delete to ensure that the hash table remains unchanged
+     while this thread is materialized.
+   */
+  if (!m_external_init)
+    init_show_var_array(OPT_SESSION, false);
+
+  /* Get and lock a validated THD from the thread manager. */
+  if ((m_safe_thd= get_THD(unsafe_thd)) != NULL)
+  {
+    DEBUG_SYNC(m_current_thd, "materialize_session_variable_array_THD_locked");
+    for (SHOW_VAR *show_var= m_show_var_array.front();
+         show_var->value && (show_var != m_show_var_array.end()); show_var++)
+    {
+      /* Resolve value, convert to text, add to cache. */
+      System_variable system_var(m_safe_thd, show_var, m_query_scope, false);
+      m_cache.push(system_var);
+    }
+
+    /* Release lock taken in get_THD(). */
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+
+    m_materialized= true;
+    ret= 0;
+  }
+
+  mysql_mutex_unlock(&LOCK_plugin_delete);
+  return ret;
+}
+
+/**
+  Allocate and assign mem_root for system variable materialization.
+*/
+void PFS_system_variable_cache::set_mem_root(void)
+{
+  if (m_mem_sysvar_ptr == NULL)
+  {
+    init_sql_alloc(PSI_INSTRUMENT_ME, &m_mem_sysvar, SYSVAR_MEMROOT_BLOCK_SIZE, 0, 0);
+    m_mem_sysvar_ptr= &m_mem_sysvar;
+  }
+  m_mem_thd= &current_thd->mem_root;      /* pointer to current THD mem_root */
+  m_mem_thd_save= *m_mem_thd;             /* restore later */
+  *m_mem_thd= &m_mem_sysvar;              /* use temporary mem_root */
+}
+
+/**
+  Mark memory blocks in the temporary mem_root as free.
+  Restore THD::mem_root.
+*/
+void PFS_system_variable_cache::clear_mem_root(void)
+{
+  if (m_mem_sysvar_ptr)
+  {
+    free_root(&m_mem_sysvar, MYF(MY_MARK_BLOCKS_FREE));
+    *m_mem_thd= m_mem_thd_save;          /* restore original mem_root */
+    m_mem_thd= NULL;
+    m_mem_thd_save= NULL;
+  }
+}
+
+/**
+  Free the temporary mem_root.
+  Restore THD::mem_root if necessary.
+*/
+void PFS_system_variable_cache::free_mem_root(void)
+{
+  if (m_mem_sysvar_ptr)
+  {
+    free_root(&m_mem_sysvar, MYF(0));
+    m_mem_sysvar_ptr= NULL;
+    if (m_mem_thd && m_mem_thd_save)
+    {
+      *m_mem_thd= m_mem_thd_save;       /* restore original mem_root */
+      m_mem_thd= NULL;
+      m_mem_thd_save= NULL;
+    }
+  }
+}
+
+/**
+  Build a SESSION system variable cache for a pfs_thread.
+  Requires that init_show_var_array() has already been called.
+  Return 0 for success.
+*/
+int PFS_system_variable_cache::do_materialize_session(PFS_thread *pfs_thread)
+{
+  int ret= 1;
+
+  m_pfs_thread= pfs_thread;
+  m_materialized= false;
+  m_cache.clear();
+
+  /* Block plugins from unloading. */
+  mysql_mutex_lock(&LOCK_plugin_delete);
+
+  /* The SHOW_VAR array must be initialized externally. */
+  assert(m_initialized);
+
+  /* Use a temporary mem_root to avoid depleting THD mem_root. */
+  if (m_use_mem_root)
+    set_mem_root();
+
+  /* Get and lock a validated THD from the thread manager. */
+  if ((m_safe_thd= get_THD(pfs_thread)) != NULL)
+  {
+    for (SHOW_VAR *show_var= m_show_var_array.front();
+         show_var->value && (show_var != m_show_var_array.end()); show_var++)
+    {
+      sys_var *value= (sys_var *)show_var->value;
+
+      /* Match the system variable scope to the target scope. */
+      if (match_scope(value->scope()))
+      {
+        /* Resolve value, convert to text, add to cache. */
+        System_variable system_var(m_safe_thd, show_var, m_query_scope, false);
+        m_cache.push(system_var);
+      }
+    }
+
+    /* Release lock taken in get_THD(). */
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+
+    m_materialized= true;
+    ret= 0;
+  }
+
+  /* Mark mem_root blocks as free. */
+  if (m_use_mem_root)
+    clear_mem_root();
+
+  mysql_mutex_unlock(&LOCK_plugin_delete);
+  return ret;
+}
+
+/**
+  Materialize a single system variable for a pfs_thread.
+  Requires that init_show_var_array() has already been called.
+  Return 0 for success.
+*/
+int PFS_system_variable_cache::do_materialize_session(PFS_thread *pfs_thread, uint index)
+{
+  int ret= 1;
+
+  m_pfs_thread= pfs_thread;
+  m_materialized= false;
+  m_cache.clear();
+
+  /* Block plugins from unloading. */
+  mysql_mutex_lock(&LOCK_plugin_delete);
+
+  /* The SHOW_VAR array must be initialized externally. */
+  assert(m_initialized);
+
+  /* Get and lock a validated THD from the thread manager. */
+  if ((m_safe_thd= get_THD(pfs_thread)) != NULL)
+  {
+    SHOW_VAR *show_var= &m_show_var_array.at(index);
+
+    if (show_var && show_var->value &&
+        (show_var != m_show_var_array.end()))
+    {
+      sys_var *value= (sys_var *)show_var->value;
+
+      /* Match the system variable scope to the target scope. */
+      if (match_scope(value->scope()))
+      {
+        /* Resolve value, convert to text, add to cache. */
+        System_variable system_var(m_safe_thd, show_var, m_query_scope, false);
+        m_cache.push(system_var);
+      }
+    }
+
+    /* Release lock taken in get_THD(). */
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+
+    m_materialized= true;
+    ret= 0;
+  }
+
+  mysql_mutex_unlock(&LOCK_plugin_delete);
+  return ret;
+}
+
+/**
+  Build a SESSION system variable cache for a THD.
+*/
+int PFS_system_variable_cache::do_materialize_session(THD *unsafe_thd)
+{
+  int ret= 1;
+
+  m_unsafe_thd= unsafe_thd;
+  m_safe_thd= NULL;
+  m_materialized= false;
+  m_cache.clear();
+
+  /* Block plugins from unloading. */
+  mysql_mutex_lock(&LOCK_plugin_delete);
+
+  /*
+     Build array of SHOW_VARs from system variable hash. Do this within
+     LOCK_plugin_delete to ensure that the hash table remains unchanged
+     while this thread is materialized.
+   */
+  if (!m_external_init)
+    init_show_var_array(OPT_SESSION, true);
+
+  /* Get and lock a validated THD from the thread manager. */
+  if ((m_safe_thd= get_THD(unsafe_thd)) != NULL)
+  {
+    for (SHOW_VAR *show_var= m_show_var_array.front();
+         show_var->value && (show_var != m_show_var_array.end()); show_var++)
+    {
+      sys_var *value = (sys_var *)show_var->value;
+
+      /* Match the system variable scope to the target scope. */
+      if (match_scope(value->scope()))
+      {
+        /* Resolve value, convert to text, add to cache. */
+        System_variable system_var(m_safe_thd, show_var, m_query_scope, false);
+        m_cache.push(system_var);
+      }
+    }
+
+    /* Release lock taken in get_THD(). */
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+
+    m_materialized= true;
+    ret= 0;
+  }
+
+  mysql_mutex_unlock(&LOCK_plugin_delete);
+  return ret;
+}
+
+
+/**
+  CLASS System_variable
+*/
+
+/**
+  Empty placeholder.
+*/
+System_variable::System_variable()
+  : m_name(NULL), m_name_length(0), m_value_length(0), m_type(SHOW_UNDEF), m_scope(0),
+    m_ignore(false), m_charset(NULL), m_initialized(false)
+{
+  m_value_str[0]= '\0';
+}
+
+/**
+  GLOBAL or SESSION system variable.
+*/
+System_variable::System_variable(THD *target_thd, const SHOW_VAR *show_var,
+                                 enum_var_type query_scope, bool ignore)
+  : m_name(NULL), m_name_length(0), m_value_length(0), m_type(SHOW_UNDEF), m_scope(0),
+    m_ignore(ignore), m_charset(NULL), m_initialized(false)
+{
+  init(target_thd, show_var, query_scope);
+}
+
+/**
+  Get sys_var value from global or local source then convert to string.
+*/
+void System_variable::init(THD *target_thd, const SHOW_VAR *show_var,
+                           enum_var_type query_scope)
+{
+  if (show_var == NULL || show_var->name == NULL)
+    return;
+
+  DBUG_ASSERT(show_var->type == SHOW_SYS);
+
+  m_name= show_var->name;
+  m_name_length= strlen(m_name);
+
+  /* Deprecated variables are ignored but must still be accounted for. */
+  if (m_ignore)
+  {
+    m_value_str[0]= '\0';
+    m_value_length= 0;
+    m_initialized= true;
+    return;
+  }
+
+  /* Block remote target thread from updating this system variable. */
+  /*XXX
+  THD *current_thread= current_thd;
+  if (target_thd != current_thread)
+    mysql_mutex_lock(&target_thd->LOCK_thd_sysvar);*/
+
+  sys_var *system_var= (sys_var *)show_var->value;
+  assert(system_var != NULL);
+  m_charset= system_var->charset(target_thd);
+  m_type= system_var->show_type();
+  m_scope= system_var->scope();
+
+  /* Get the value of the system variable. */
+  String buf(m_value_str, sizeof(m_value_str) - 1, system_charset_info);
+  if (!system_var->val_str_nolock(&buf, target_thd,
+               system_var->value_ptr(target_thd, query_scope, &null_clex_str)))
+    buf.length(0);
+
+  m_value_length= MY_MIN(buf.length(), SHOW_VAR_FUNC_BUFF_SIZE);
+
+  /* Returned value may reference a string other than m_value_str. */
+  if (buf.ptr() != m_value_str)
+    memcpy(m_value_str, buf.ptr(), m_value_length);
+  m_value_str[m_value_length]= 0;
+
+  /*XXX
+  if (target_thd != current_thread)
+    mysql_mutex_unlock(&target_thd->LOCK_thd_sysvar);*/
+
+  m_initialized= true;
+}
+
+
+/**
+  CLASS PFS_status_variable_cache
+*/
+
+PFS_status_variable_cache::
+PFS_status_variable_cache(bool external_init) :
+                          PFS_variable_cache<Status_variable>(external_init),
+                          m_show_command(false), m_sum_client_status(NULL)
+{
+  /* Determine if the originating query is a SHOW command. */
+  m_show_command= (m_current_thd->lex->sql_command == SQLCOM_SHOW_STATUS);
+}
+
+/**
+  Build cache of SESSION status variables for a user.
+*/
+int PFS_status_variable_cache::materialize_user(PFS_user *pfs_user)
+{
+  if (!pfs_user)
+    return 1;
+
+  if (is_materialized(pfs_user))
+    return 0;
+
+  if (!pfs_user->m_lock.is_populated())
+    return 1;
+
+  /* Set callback function. */
+  m_sum_client_status= sum_user_status;
+  return do_materialize_client((PFS_client *)pfs_user);
+}
+
+/**
+  Build cache of SESSION status variables for a host.
+*/
+int PFS_status_variable_cache::materialize_host(PFS_host *pfs_host)
+{
+  if (!pfs_host)
+    return 1;
+
+  if (is_materialized(pfs_host))
+    return 0;
+
+  if (!pfs_host->m_lock.is_populated())
+    return 1;
+
+  /* Set callback function. */
+  m_sum_client_status= sum_host_status;
+  return do_materialize_client((PFS_client *)pfs_host);
+}
+
+/**
+  Build cache of SESSION status variables for an account.
+*/
+int PFS_status_variable_cache::materialize_account(PFS_account *pfs_account)
+{
+  if (!pfs_account)
+    return 1;
+
+  if (is_materialized(pfs_account))
+    return 0;
+
+  if (!pfs_account->m_lock.is_populated())
+    return 1;
+
+  /* Set callback function. */
+  m_sum_client_status= sum_account_status;
+  return do_materialize_client((PFS_client *)pfs_account);
+}
+/**
+  Compare status variable scope to desired scope.
+  @param variable_scope         Scope of current status variable
+  @return TRUE if variable matches the query scope
+*/
+bool PFS_status_variable_cache::match_scope(SHOW_SCOPE variable_scope, bool strict)
+{
+  switch (variable_scope)
+  {
+    case SHOW_SCOPE_GLOBAL:
+      return (m_query_scope == OPT_GLOBAL) || (! strict && (m_query_scope == OPT_SESSION));
+      break;
+    case SHOW_SCOPE_SESSION:
+      /* Ignore session-only vars if aggregating by user, host or account. */
+      if (m_aggregate)
+        return false;
+      else
+        return (m_query_scope == OPT_SESSION);
+      break;
+    case SHOW_SCOPE_ALL:
+      return (m_query_scope == OPT_GLOBAL || m_query_scope == OPT_SESSION);
+      break;
+    case SHOW_SCOPE_UNDEF:
+    default:
+      return false;
+      break;
+  }
+  return false;
+}
+
+/*
+  Exclude specific status variables from the query by name or prefix.
+  Return TRUE if variable should be filtered.
+*/
+bool PFS_status_variable_cache::filter_by_name(const SHOW_VAR *show_var)
+{
+  assert(show_var);
+  assert(show_var->name);
+
+  if (show_var->type == SHOW_ARRAY)
+  {
+    /* The SHOW_ARRAY name is the prefix for the variables in the subarray. */
+    const char *prefix= show_var->name;
+    /* Exclude COM counters if not a SHOW STATUS command. */
+    if (!my_strcasecmp(system_charset_info, prefix, "Com") && !m_show_command)
+      return true;
+  }
+  else
+  {
+    /*
+      Slave status resides in Performance Schema replication tables. Exclude
+      these slave status variables from the SHOW STATUS command and from the
+      status tables.
+      Assume null prefix to ensure that only server-defined slave status
+      variables are filtered.
+    */
+    const char *name= show_var->name;
+    if (!my_strcasecmp(system_charset_info, name, "Slave_running") ||
+        !my_strcasecmp(system_charset_info, name, "Slave_retried_transactions") ||
+        !my_strcasecmp(system_charset_info, name, "Slave_last_heartbeat") ||
+        !my_strcasecmp(system_charset_info, name, "Slave_received_heartbeats") ||
+        !my_strcasecmp(system_charset_info, name, "Slave_heartbeat_period"))
+    {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+/**
+  Check that the variable type is aggregatable.
+
+  @param variable_type         Status variable type
+  @return TRUE if variable type can be aggregated
+*/
+bool PFS_status_variable_cache::can_aggregate(enum_mysql_show_type variable_type)
+{
+  switch(variable_type)
+  {
+    /*
+      All server status counters that are totaled across threads are defined in
+      system_status_var as either SHOW_LONGLONG_STATUS or SHOW_LONG_STATUS.
+      These data types are not available to plugins.
+    */
+    case SHOW_LONGLONG_STATUS:
+    case SHOW_LONG_STATUS:
+      return true;
+      break;
+
+    /* Server and plugin */
+    case SHOW_UNDEF:
+    case SHOW_BOOL:
+    case SHOW_CHAR:
+    case SHOW_CHAR_PTR:
+    case SHOW_ARRAY:
+    case SHOW_FUNC:
+    case SHOW_INT:
+    case SHOW_LONG:
+    case SHOW_LONGLONG:
+    case SHOW_DOUBLE:
+    /* Server only */
+    case SHOW_HAVE:
+    case SHOW_MY_BOOL:
+    case SHOW_SYS:
+    case SHOW_LEX_STRING:
+    case SHOW_KEY_CACHE_LONG:
+    case SHOW_DOUBLE_STATUS:
+    case SHOW_HA_ROWS:
+    case SHOW_LONG_NOFLUSH:
+    case SHOW_SLONG:
+    default:
+      return false;
+      break;
+  }
+}
+
+/**
+  Check if a status variable should be excluded from the query.
+  Return TRUE if the variable should be excluded.
+*/
+bool PFS_status_variable_cache::filter_show_var(const SHOW_VAR *show_var, bool strict)
+{
+  /* Match the variable scope with the query scope. */
+  if (!match_scope(show_scope_from_type(show_var->type), strict))
+    return true;
+
+  /* Exclude specific status variables by name or prefix. */
+  if (filter_by_name(show_var))
+    return true;
+
+  /* For user, host or account, ignore variables having non-aggregatable types. */
+  if (m_aggregate && !can_aggregate(show_var->type))
+    return true;
+
+  return false;
+}
+
+
+/**
+  Build an array of SHOW_VARs from the global status array. Expand nested
+  subarrays, filter unwanted variables.
+  NOTE: Must be done inside of LOCK_status to guard against plugin load/unload.
+*/
+bool PFS_status_variable_cache::init_show_var_array(enum_var_type scope, bool strict)
+{
+  assert(!m_initialized);
+
+  /* Resize if necessary. */
+  m_show_var_array.reserve(all_status_vars.elements + 1);
+
+  m_query_scope= scope;
+
+  for (SHOW_VAR *show_var_iter= dynamic_element(&all_status_vars, 0, SHOW_VAR *);
+       show_var_iter != dynamic_element(&all_status_vars, all_status_vars.elements, SHOW_VAR *);
+       show_var_iter++)
+  {
+    SHOW_VAR show_var= *show_var_iter;
+
+    /* Check if this status var should be excluded from the query. */
+    if (filter_show_var(&show_var, strict))
+      continue;
+
+    if (show_var.type == SHOW_ARRAY)
+    {
+      /* Expand nested subarray. The name is used as a prefix. */
+      expand_show_var_array((SHOW_VAR *)show_var.value, show_var.name, strict);
+    }
+    else
+    {
+      show_var.name= make_show_var_name(NULL, show_var.name);
+      m_show_var_array.push(show_var);
+    }
+  }
+
+  /* Last element is NULL. */
+  st_mysql_show_var empty= {0,0,SHOW_UNDEF};
+  m_show_var_array.push(empty);
+
+  /* Get the latest version of all_status_vars. */
+  m_version= get_status_vars_version();
+
+  /* Increase cache size if necessary. */
+  m_cache.reserve(m_show_var_array.elements());
+
+  m_initialized= true;
+  return true;
+}
+
+/**
+  Expand a nested subarray of status variables, indicated by a type of SHOW_ARRAY.
+*/
+void PFS_status_variable_cache::expand_show_var_array(const SHOW_VAR *show_var_array, const char *prefix, bool strict)
+{
+  for (const SHOW_VAR *show_var_ptr= show_var_array;
+       show_var_ptr && show_var_ptr->name;
+       show_var_ptr++)
+  {
+    SHOW_VAR show_var= *show_var_ptr;
+
+    if (filter_show_var(&show_var, strict))
+      continue;
+
+    if (show_var.type == SHOW_ARRAY)
+    {
+      char name_buf[SHOW_VAR_MAX_NAME_LEN];
+      show_var.name= make_show_var_name(prefix, show_var.name, name_buf, sizeof(name_buf));
+      /* Expand nested subarray. The name is used as a prefix. */
+      expand_show_var_array((SHOW_VAR *)show_var.value, show_var.name, strict);
+    }
+    else
+    {
+      /* Add the SHOW_VAR element. Make a local copy of the name string. */
+      show_var.name= make_show_var_name(prefix, show_var.name);
+      m_show_var_array.push(show_var);
+    }
+  }
+}
+
+/**
+  Build the complete status variable name, with prefix. Return in buffer provided.
+*/
+char * PFS_status_variable_cache::make_show_var_name(const char* prefix, const char* name,
+                                                     char *name_buf, size_t buf_len)
+{
+  assert(name_buf != NULL);
+  char *prefix_end= name_buf;
+
+  if (prefix && *prefix)
+  {
+    /* Drop the prefix into the front of the name buffer. */
+    prefix_end= my_stpnmov(name_buf, prefix, buf_len-1);
+    *prefix_end++= '_';
+  }
+
+  /* Restrict name length to remaining buffer size. */
+  size_t max_name_len= name_buf + buf_len - prefix_end;
+
+  /* Load the name into the buffer after the prefix. */
+  my_stpnmov(prefix_end, name, max_name_len);
+  name_buf[buf_len-1]= 0;
+
+  return (name_buf);
+}
+
+/**
+  Make a copy of the name string prefixed with the subarray name if necessary.
+*/
+char * PFS_status_variable_cache::make_show_var_name(const char* prefix, const char* name)
+{
+  char name_buf[SHOW_VAR_MAX_NAME_LEN];
+  size_t buf_len= sizeof(name_buf);
+  make_show_var_name(prefix, name, name_buf, buf_len);
+  return m_current_thd->strdup(name_buf); /* freed at statement end */
+}
+
+/**
+  Build an internal SHOW_VAR array from the external status variable array.
+*/
+bool PFS_status_variable_cache::do_initialize_session(void)
+{
+  /* Acquire LOCK_status to guard against plugin load/unload. */
+  //if (m_current_thd->fill_status_recursion_level++ == 0)
+    mysql_mutex_lock(&LOCK_status);
+
+  bool ret= init_show_var_array(OPT_SESSION, true);
+
+  //if (m_current_thd->fill_status_recursion_level-- == 1)
+    mysql_mutex_unlock(&LOCK_status);
+
+  return ret;
+}
+
+/**
+  For the current THD, use initial_status_vars taken from before the query start.
+*/
+STATUS_VAR *PFS_status_variable_cache::set_status_vars(void)
+{
+  STATUS_VAR *status_vars;
+  if (m_safe_thd == m_current_thd && m_current_thd->initial_status_var != NULL)
+    status_vars= m_current_thd->initial_status_var;
+  else
+    status_vars= &m_safe_thd->status_var;
+
+  return status_vars;
+}
+
+/**
+  Build cache for GLOBAL status variables using values totaled from all threads.
+*/
+int PFS_status_variable_cache::do_materialize_global(void)
+{
+  STATUS_VAR status_totals;
+
+  m_materialized= false;
+  DEBUG_SYNC(m_current_thd, "before_materialize_global_status_array");
+
+  /* Acquire LOCK_status to guard against plugin load/unload. */
+  //if (m_current_thd->fill_status_recursion_level++ == 0)
+    mysql_mutex_lock(&LOCK_status);
+
+  /*
+     Build array of SHOW_VARs from global status array. Do this within
+     LOCK_status to ensure that the array remains unchanged during
+     materialization.
+   */
+  if (!m_external_init)
+    init_show_var_array(OPT_GLOBAL, true);
+
+  /*
+    Collect totals for all active threads. Start with global status vars as a
+    baseline.
+  */
+  PFS_connection_status_visitor visitor(&status_totals);
+  PFS_connection_iterator::visit_global(false, /* hosts */
+                                        false, /* users */
+                                        false, /* accounts */
+                                        false, /* threads */
+                                        true,  /* THDs */
+                                        &visitor);
+  /*
+    Build the status variable cache using the SHOW_VAR array as a reference.
+    Use the status totals collected from all threads.
+  */
+  manifest(m_current_thd, m_show_var_array.front(), &status_totals, "", false, true);
+
+  //if (m_current_thd->fill_status_recursion_level-- == 1)
+    mysql_mutex_unlock(&LOCK_status);
+
+  m_materialized= true;
+  DEBUG_SYNC(m_current_thd, "after_materialize_global_status_array");
+
+  return 0;
+}
+
+/**
+  Build GLOBAL and SESSION status variable cache using values for a non-instrumented thread.
+*/
+int PFS_status_variable_cache::do_materialize_all(THD* unsafe_thd)
+{
+  int ret= 1;
+  assert(unsafe_thd != NULL);
+
+  m_unsafe_thd= unsafe_thd;
+  m_materialized= false;
+  m_cache.clear();
+
+  /* Avoid recursive acquisition of LOCK_status. */
+  //if (m_current_thd->fill_status_recursion_level++ == 0)
+    mysql_mutex_lock(&LOCK_status);
+
+  /*
+     Build array of SHOW_VARs from global status array. Do this within
+     LOCK_status to ensure that the array remains unchanged while this
+     thread is materialized.
+   */
+  if (!m_external_init)
+    init_show_var_array(OPT_SESSION, false);
+
+    /* Get and lock a validated THD from the thread manager. */
+  if ((m_safe_thd= get_THD(unsafe_thd)) != NULL)
+  {
+    /*
+      Build the status variable cache using the SHOW_VAR array as a reference.
+      Use the status values from the THD protected by the thread manager lock.
+    */
+    STATUS_VAR *status_vars= set_status_vars();
+    manifest(m_safe_thd, m_show_var_array.front(), status_vars, "", false, false);
+
+    /* Release lock taken in get_THD(). */
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+
+    m_materialized= true;
+    ret= 0;
+  }
+
+  //if (m_current_thd->fill_status_recursion_level-- == 1)
+    mysql_mutex_unlock(&LOCK_status);
+  return ret;
+}
+
+/**
+  Build SESSION status variable cache using values for a non-instrumented thread.
+*/
+int PFS_status_variable_cache::do_materialize_session(THD* unsafe_thd)
+{
+  int ret= 1;
+  assert(unsafe_thd != NULL);
+
+  m_unsafe_thd= unsafe_thd;
+  m_materialized= false;
+  m_cache.clear();
+
+  /* Avoid recursive acquisition of LOCK_status. */
+  //if (m_current_thd->fill_status_recursion_level++ == 0)
+    mysql_mutex_lock(&LOCK_status);
+
+  /*
+     Build array of SHOW_VARs from global status array. Do this within
+     LOCK_status to ensure that the array remains unchanged while this
+     thread is materialized.
+   */
+  if (!m_external_init)
+    init_show_var_array(OPT_SESSION, true);
+
+    /* Get and lock a validated THD from the thread manager. */
+  if ((m_safe_thd= get_THD(unsafe_thd)) != NULL)
+  {
+    /*
+      Build the status variable cache using the SHOW_VAR array as a reference.
+      Use the status values from the THD protected by the thread manager lock.
+    */
+    STATUS_VAR *status_vars= set_status_vars();
+    manifest(m_safe_thd, m_show_var_array.front(), status_vars, "", false, true);
+
+    /* Release lock taken in get_THD(). */
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+
+    m_materialized= true;
+    ret= 0;
+  }
+
+  //if (m_current_thd->fill_status_recursion_level-- == 1)
+    mysql_mutex_unlock(&LOCK_status);
+  return ret;
+}
+
+/**
+  Build SESSION status variable cache using values for a PFS_thread.
+  NOTE: Requires that init_show_var_array() has already been called.
+*/
+int PFS_status_variable_cache::do_materialize_session(PFS_thread *pfs_thread)
+{
+  int ret= 1;
+  assert(pfs_thread != NULL);
+
+  m_pfs_thread= pfs_thread;
+  m_materialized= false;
+  m_cache.clear();
+
+  /* Acquire LOCK_status to guard against plugin load/unload. */
+  //if (m_current_thd->fill_status_recursion_level++ == 0)
+    mysql_mutex_lock(&LOCK_status);
+
+  /* The SHOW_VAR array must be initialized externally. */
+  assert(m_initialized);
+
+    /* Get and lock a validated THD from the thread manager. */
+  if ((m_safe_thd= get_THD(pfs_thread)) != NULL)
+  {
+    /*
+      Build the status variable cache using the SHOW_VAR array as a reference.
+      Use the status values from the THD protected by the thread manager lock.
+    */
+    STATUS_VAR *status_vars= set_status_vars();
+    manifest(m_safe_thd, m_show_var_array.front(), status_vars, "", false, true);
+
+    /* Release lock taken in get_THD(). */
+    mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
+
+    m_materialized= true;
+    ret= 0;
+  }
+
+  //if (m_current_thd->fill_status_recursion_level-- == 1)
+    mysql_mutex_unlock(&LOCK_status);
+  return ret;
+}
+
+/**
+  Build cache of SESSION status variables using the status values provided.
+  The cache is associated with a user, host or account, but not with any
+  particular thread.
+  NOTE: Requires that init_show_var_array() has already been called.
+*/
+int PFS_status_variable_cache::do_materialize_client(PFS_client *pfs_client)
+{
+  assert(pfs_client != NULL);
+  STATUS_VAR status_totals;
+
+  m_pfs_client= pfs_client;
+  m_materialized= false;
+  m_cache.clear();
+
+  /* Acquire LOCK_status to guard against plugin load/unload. */
+  //if (m_current_thd->fill_status_recursion_level++ == 0)
+    mysql_mutex_lock(&LOCK_status);
+
+  /* The SHOW_VAR array must be initialized externally. */
+  assert(m_initialized);
+
+  /*
+    Generate status totals from active threads and from totals aggregated
+    from disconnected threads.
+  */
+  m_sum_client_status(pfs_client, &status_totals);
+
+  /*
+    Build the status variable cache using the SHOW_VAR array as a reference and
+    the status totals collected from threads associated with this client.
+  */
+  manifest(m_current_thd, m_show_var_array.front(), &status_totals, "", false, true);
+
+  //if (m_current_thd->fill_status_recursion_level-- == 1)
+    mysql_mutex_unlock(&LOCK_status);
+
+  m_materialized= true;
+  return 0;
+}
+
+/*
+  Build the status variable cache from the expanded and sorted SHOW_VAR array.
+  Resolve status values using the STATUS_VAR struct provided.
+*/
+void PFS_status_variable_cache::manifest(THD *thd, const SHOW_VAR *show_var_array,
+                                    STATUS_VAR *status_vars, const char *prefix,
+                                    bool nested_array, bool strict)
+{
+  for (const SHOW_VAR *show_var_iter= show_var_array;
+       show_var_iter && show_var_iter->name;
+       show_var_iter++)
+  {
+    // work buffer, must be aligned to handle long/longlong values
+    my_aligned_storage<SHOW_VAR_FUNC_BUFF_SIZE+1, MY_ALIGNOF(longlong)>
+      value_buf;
+    SHOW_VAR show_var_tmp;
+    const SHOW_VAR *show_var_ptr= show_var_iter;  /* preserve array pointer */
+
+    /*
+      If the value is a function reference, then execute the function and
+      reevaluate the new SHOW_TYPE and value. Handle nested case where
+      SHOW_FUNC resolves to another SHOW_FUNC.
+    */
+    if (show_var_ptr->type == SHOW_FUNC)
+    {
+      show_var_tmp= *show_var_ptr;
+      /*
+        Execute the function reference in show_var_tmp->value, which returns
+        show_var_tmp with a new type and new value.
+      */
+      for (const SHOW_VAR *var= show_var_ptr; var->type == SHOW_FUNC; var= &show_var_tmp)
+      {
+        ((mysql_show_var_func)(var->value))(thd, &show_var_tmp, value_buf.data, NULL, m_query_scope);
+      }
+      show_var_ptr= &show_var_tmp;
+    }
+
+    /*
+      If we are expanding a SHOW_ARRAY, filter variables that were not prefiltered by
+      init_show_var_array().
+    */
+    if (nested_array && filter_show_var(show_var_ptr, strict))
+      continue;
+
+    if (show_var_ptr->type == SHOW_ARRAY)
+    {
+      /*
+        Status variables of type SHOW_ARRAY were expanded and filtered by
+        init_show_var_array(), except where a SHOW_FUNC resolves into a
+        SHOW_ARRAY, such as with InnoDB. Recurse to expand the subarray.
+      */
+      manifest(thd, (SHOW_VAR *)show_var_ptr->value, status_vars, show_var_ptr->name, true, strict);
+    }
+    else
+    {
+      /* Add the materialized status variable to the cache. */
+      SHOW_VAR show_var= *show_var_ptr;
+      /*
+        For nested array expansions, make a copy of the variable name, just as
+        done in init_show_var_array().
+      */
+      if (nested_array)
+        show_var.name= make_show_var_name(prefix, show_var_ptr->name);
+
+      /* Convert status value to string format. Add to the cache. */
+      Status_variable status_var(&show_var, status_vars, m_query_scope);
+      m_cache.push(status_var);
+    }
+  }
+}
+
+/**
+  CLASS Status_variable
+*/
+Status_variable::Status_variable(const SHOW_VAR *show_var, STATUS_VAR *status_vars, enum_var_type query_scope)
+  : m_name_length(0), m_value_length(0), m_type(SHOW_UNDEF),
+    m_charset(NULL), m_initialized(false)
+{
+  init(show_var, status_vars, query_scope);
+}
+
+/**
+  Resolve status value, convert to string.
+  show_var->value is an offset into status_vars.
+  NOTE: Assumes LOCK_status is held.
+*/
+void Status_variable::init(const SHOW_VAR *show_var, STATUS_VAR *status_vars, enum_var_type query_scope)
+{
+  if (show_var == NULL || show_var->name == NULL)
+    return;
+  m_name= show_var->name;
+  m_name_length= strlen(m_name);
+  m_type= show_var->type;
+
+  /* Get the value of the status variable. */
+  const char *value;
+  value= get_one_variable(current_thd, show_var, query_scope, m_type,
+                          status_vars, &m_charset, m_value_str, &m_value_length);
+  m_value_length= MY_MIN(m_value_length, SHOW_VAR_FUNC_BUFF_SIZE);
+  m_charset= system_charset_info;
+
+  /* Returned value may reference a string other than m_value_str. */
+  if (value != m_value_str)
+    memcpy(m_value_str, value, m_value_length);
+  m_value_str[m_value_length]= 0;
+
+  m_initialized= true;
+}
+
+/*
+  Get status totals for this user from active THDs and related accounts.
+*/
+void sum_user_status(PFS_client *pfs_user, STATUS_VAR *status_totals)
+{
+  PFS_connection_status_visitor visitor(status_totals);
+  PFS_connection_iterator::visit_user((PFS_user *)pfs_user,
+                                                  true,  /* accounts */
+                                                  false, /* threads */
+                                                  true,  /* THDs */
+                                                  &visitor);
+}
+
+/*
+  Get status totals for this host from active THDs and related accounts.
+*/
+void sum_host_status(PFS_client *pfs_host, STATUS_VAR *status_totals)
+{
+  PFS_connection_status_visitor visitor(status_totals);
+  PFS_connection_iterator::visit_host((PFS_host *)pfs_host,
+                                                  true,  /* accounts */
+                                                  false, /* threads */
+                                                  true,  /* THDs */
+                                                  &visitor);
+}
+
+/*
+  Get status totals for this account from active THDs and from totals aggregated
+  from disconnectd threads.
+*/
+void sum_account_status(PFS_client *pfs_account, STATUS_VAR *status_totals)
+{
+  PFS_connection_status_visitor visitor(status_totals);
+  PFS_connection_iterator::visit_account((PFS_account *)pfs_account,
+                                                        false,      /* threads */
+                                                        true,       /* THDs */
+                                                        &visitor);
+}
+
+/**
+  Reset aggregated status counter stats for account, user and host.
+  NOTE: Assumes LOCK_status is held.
+*/
+void reset_pfs_status_stats()
+{
+  reset_status_by_account();
+  reset_status_by_user();
+  reset_status_by_host();
+}
+
+/** @} */