1 files changed, 235 insertions, 0 deletions
diff --git a/storage/perfschema/table_variables_by_thread.cc b/storage/perfschema/table_variables_by_thread.cc
new file mode 100644
index 00000000..db9e4c2c
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+++ b/storage/perfschema/table_variables_by_thread.cc
@@ -0,0 +1,235 @@
+/* Copyright (c) 2015, 2022, Oracle and/or its affiliates.
+
+  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 St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+/**
+  @file storage/perfschema/table_variables_by_thread.cc
+  Table VARIABLES_BY_THREAD (implementation).
+*/
+
+#include "my_global.h"
+#include "table_variables_by_thread.h"
+#include "my_thread.h"
+#include "pfs_instr_class.h"
+#include "pfs_column_types.h"
+#include "pfs_column_values.h"
+#include "pfs_global.h"
+
+THR_LOCK table_variables_by_thread::m_table_lock;
+
+PFS_engine_table_share_state
+table_variables_by_thread::m_share_state = {
+  false /* m_checked */
+};
+
+PFS_engine_table_share
+table_variables_by_thread::m_share=
+{
+  { C_STRING_WITH_LEN("variables_by_thread") },
+  &pfs_readonly_acl,
+  table_variables_by_thread::create,
+  NULL, /* write_row */
+  NULL, /* delete_all_rows */
+  table_variables_by_thread::get_row_count,
+  sizeof(pos_t),
+  &m_table_lock,
+  { C_STRING_WITH_LEN("CREATE TABLE user_variables_by_thread("
+  "THREAD_ID BIGINT unsigned not null,"
+  "VARIABLE_NAME VARCHAR(64) not null,"
+  "VARIABLE_VALUE VARCHAR(1024))") },
+  true, /* m_perpetual */
+  &m_share_state
+};
+
+PFS_engine_table*
+table_variables_by_thread::create(void)
+{
+  return new table_variables_by_thread();
+}
+
+ha_rows table_variables_by_thread::get_row_count(void)
+{
+  mysql_mutex_lock(&LOCK_plugin_delete);
+  mysql_prlock_rdlock(&LOCK_system_variables_hash);
+  ulong system_var_count= get_system_variable_hash_records();
+  mysql_prlock_unlock(&LOCK_system_variables_hash);
+  mysql_mutex_unlock(&LOCK_plugin_delete);
+  return (global_thread_container.get_row_count() * system_var_count);
+}
+
+table_variables_by_thread::table_variables_by_thread()
+  : PFS_engine_table(&m_share, &m_pos),
+    m_sysvar_cache(true), m_row_exists(false), m_pos(), m_next_pos(), m_context(NULL)
+{}
+
+void table_variables_by_thread::reset_position(void)
+{
+  m_pos.reset();
+  m_next_pos.reset();
+}
+
+int table_variables_by_thread::rnd_init(bool scan)
+{
+  /*
+    Build array of SHOW_VARs from system variable hash prior to materializing
+    threads in rnd_next() or rnd_pos().
+  */
+  m_sysvar_cache.initialize_session();
+
+  /* Record the version of the system variable hash. */
+  ulonglong hash_version= m_sysvar_cache.get_sysvar_hash_version();
+
+  /*
+    The table context holds the current version of the system variable hash and
+    a record of which threads were materialized.
+    If scan == true, then allocate a new context from mem_root and store in TLS.
+    If scan == false, then restore from TLS.
+  */
+  m_context= (table_variables_by_thread_context *)current_thd->alloc(sizeof(table_variables_by_thread_context));
+  new(m_context) table_variables_by_thread_context(hash_version, !scan);
+  return 0;
+}
+
+int table_variables_by_thread::rnd_next(void)
+{
+  /* If system variable hash changes, exit with warning. */ // TODO: Issue warning
+  if (!m_context->versions_match())
+    return HA_ERR_END_OF_FILE;
+
+  bool has_more_thread= true;
+
+  for (m_pos.set_at(&m_next_pos);
+       has_more_thread;
+       m_pos.next_thread())
+  {
+    PFS_thread *pfs_thread= global_thread_container.get(m_pos.m_index_1, &has_more_thread);
+
+    /* Materialize all variables for the current thread. Assign a dedicated mem_root. */
+    if (m_sysvar_cache.materialize_session(pfs_thread, true) == 0)
+    {
+      /* Mark this thread as materialized. */
+      m_context->set_item(m_pos.m_index_1);
+
+      const System_variable *system_var= m_sysvar_cache.get(m_pos.m_index_2);
+      if (system_var != NULL)
+      {
+        make_row(pfs_thread, system_var);
+        m_next_pos.set_after(&m_pos);
+        return 0;
+      }
+    }
+  }
+  return HA_ERR_END_OF_FILE;
+}
+
+int
+table_variables_by_thread::rnd_pos(const void *pos)
+{
+  /* If system variable hash changes, do nothing. */
+  if (!m_context->versions_match())
+    return HA_ERR_RECORD_DELETED;
+
+  set_position(pos);
+  assert(m_pos.m_index_1 < global_thread_container.get_row_count());
+
+  PFS_thread *pfs_thread= global_thread_container.get(m_pos.m_index_1);
+    /*
+    Only materialize threads that were previously materialized by rnd_next().
+    If a thread cannot be rematerialized, then do nothing.
+    Only materialize the requested system variable to avoid repeated
+    materialization of each thread, such as with ORDER BY variable_name.
+  */
+  if (m_context->is_item_set(m_pos.m_index_1) &&
+      /* Materialize only the requested variable. */
+      m_sysvar_cache.materialize_session(pfs_thread, m_pos.m_index_2) == 0)
+  {
+    /* Get the first (and only) element from the cache. */
+    const System_variable *system_var= m_sysvar_cache.get();
+    if (system_var != NULL)
+    {
+      make_row(pfs_thread, system_var);
+      m_next_pos.set_after(&m_pos);
+      return 0;
+    }
+  }
+  return HA_ERR_RECORD_DELETED;
+}
+
+void table_variables_by_thread
+::make_row(PFS_thread *thread, const System_variable *system_var)
+{
+  pfs_optimistic_state lock;
+  m_row_exists= false;
+  if (system_var->is_null() || system_var->is_ignored())
+    return;
+
+  /* Protect this reader against a thread termination */
+  thread->m_lock.begin_optimistic_lock(&lock);
+
+  m_row.m_thread_internal_id= thread->m_thread_internal_id;
+  m_row.m_variable_name.make_row(system_var->m_name, system_var->m_name_length);
+  m_row.m_variable_value.make_row(system_var);
+
+  if (!thread->m_lock.end_optimistic_lock(&lock))
+    return;
+
+  m_row_exists= true;
+}
+
+int table_variables_by_thread
+::read_row_values(TABLE *table,
+                  unsigned char *buf,
+                  Field **fields,
+                  bool read_all)
+{
+  Field *f;
+
+  if (unlikely(! m_row_exists))
+    return HA_ERR_RECORD_DELETED;
+
+  /* Set the null bits */
+  assert(table->s->null_bytes == 1);
+  buf[0]= 0;
+
+  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: /* VARIABLE_NAME */
+        set_field_varchar_utf8(f, m_row.m_variable_name.m_str, m_row.m_variable_name.m_length);
+        break;
+      case 2: /* VARIABLE_VALUE */
+        m_row.m_variable_value.set_field(f);
+        break;
+      default:
+        assert(false);
+      }
+    }
+  }
+
+  return 0;
+}
+