ndb/plugin/ndb_schema_dist_table.cc

/*
   Copyright (c) 2018, 2019, 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, 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
*/

// Implements the interface defined in
#include "storage/ndb/plugin/ndb_schema_dist_table.h"

#include <sstream>

#include "sql/item_strfunc.h"
#include "storage/ndb/plugin/ndb_log.h"
#include "storage/ndb/plugin/ndb_retry.h"
#include "storage/ndb/plugin/ndb_schema_dist.h"
#include "storage/ndb/plugin/ndb_thd_ndb.h"

const std::string Ndb_schema_dist_table::DB_NAME = "mysql";
const std::string Ndb_schema_dist_table::TABLE_NAME = "ndb_schema";

const char *Ndb_schema_dist_table::COL_DB = "db";
const char *Ndb_schema_dist_table::COL_NAME = "name";
const char *Ndb_schema_dist_table::COL_QUERY = "query";
const char *Ndb_schema_dist_table::COL_ID = "id";
const char *Ndb_schema_dist_table::COL_VERSION = "version";
std::string Ndb_schema_dist_table::old_ndb_schema_uuid = "";
static const char *COL_SLOCK = "slock";
static const char *COL_NODEID = "node_id";
static const char *COL_EPOCH = "epoch";
static const char *COL_TYPE = "type";
static const char *COL_SCHEMA_OP_ID = "schema_op_id";

// Length of the schema object identifiers which can be distributed by the
// ndb_schema table. The legacy limit of 63 was increased in 8.0.18 to allow for
// "any" identifier to be distributed. NOTE! Code still supports working with a
// ndb_schema table using the legacy length, warning will be printed suggesting
// upgrade
static constexpr int IDENTIFIER_LENGTH = 255;
static constexpr int LEGACY_IDENTIFIER_LENGTH = 63;

static const char *SCHEMA_UUID_KEY = "schema_uuid";

Ndb_schema_dist_table::Ndb_schema_dist_table(Thd_ndb *thd_ndb)
    : Ndb_util_table(thd_ndb, DB_NAME, TABLE_NAME, true) {}

Ndb_schema_dist_table::~Ndb_schema_dist_table() {}

bool Ndb_schema_dist_table::check_schema() const {
  // db
  // varbinary, at least 63 bytes long
  // NOTE! The 63 bytes length for the db and name column is a legacy bug
  // which doesn't have enough room for MySQL's max identitfier size. For
  // backwards compatiblity reasons it's allowed to use such a schema
  // distribution table but not all identifiers will be possible to distribute.
  if (!(check_column_exist(COL_DB) && check_column_varbinary(COL_DB) &&
        check_column_minlength(COL_DB, LEGACY_IDENTIFIER_LENGTH))) {
    return false;
  }

  // name
  // varbinary, at least 63 bytes long
  if (!(check_column_exist(COL_NAME) && check_column_varbinary(COL_NAME) &&
        check_column_minlength(COL_NAME, LEGACY_IDENTIFIER_LENGTH))) {
    return false;
  }
  // Check that db + name is the primary key, otherwise pk operations
  // using that key won't work
  if (!check_primary_key({COL_DB, COL_NAME})) {
    return false;
  }

  // slock
  // binary, need room for at least 32 bytes(i.e 32*8 bits for 256 nodes)
  if (!(check_column_exist(COL_SLOCK) && check_column_binary(COL_SLOCK) &&
        check_column_minlength(COL_SLOCK, 32))) {
    return false;
  }

  // query
  // blob
  if (!(check_column_exist(COL_QUERY) && check_column_blob(COL_QUERY))) {
    return false;
  }

  // nodeid
  // unsigned int
  if (!(check_column_exist(COL_NODEID) && check_column_unsigned(COL_NODEID))) {
    return false;
  }

  // epoch
  // unsigned bigint
  if (!(check_column_exist(COL_EPOCH) && check_column_bigunsigned(COL_EPOCH))) {
    return false;
  }

  // id
  // unsigned int
  if (!(check_column_exist(COL_ID) && check_column_unsigned(COL_ID))) {
    return false;
  }

  // version
  // unsigned int
  if (!(check_column_exist(COL_VERSION) &&
        check_column_unsigned(COL_VERSION))) {
    return false;
  }

  // type
  // unsigned int
  if (!(check_column_exist(COL_TYPE) && check_column_unsigned(COL_TYPE))) {
    return false;
  }

  // schema_op_id
  // unsigned int
  if (!check_column_exist(COL_SCHEMA_OP_ID)) {
    // This is an optional column added in 8.0.17. Functionality depending on
    // this column will be conditional but warnings are pushed to alert the user
    // that upgrade is eventually necessary
    ;
  } else {
    // Column exists, check proper type
    if (!(check_column_unsigned(COL_SCHEMA_OP_ID) &&
          check_column_nullable(COL_SCHEMA_OP_ID, true))) {
      return false;
    }
  }

  return true;
}

bool Ndb_schema_dist_table::check_column_identifier_limit(
    const char *column_name, const std::string &identifier) const {
  DBUG_TRACE;
  DBUG_PRINT("enter", ("column_name: '%s', identifier: '%s'", column_name,
                       identifier.c_str()));

  if (!check_column_exist(column_name)) {
    return false;
  }

  const int max_length = DBUG_EVALUATE_IF("ndb_schema_dist_63byte_limit", 63,
                                          get_column_max_length(column_name));

  if (identifier.length() > static_cast<size_t>(max_length)) {
    push_warning("Identifier length exceeds the %d byte limit", max_length);
    return false;
  }
  return true;
}

bool Ndb_schema_dist_table::define_table_ndb(NdbDictionary::Table &new_table,
                                             unsigned mysql_version) const {
  // Set metadata for backwards compatibility support, earlier versions
  // will see what they expect and can connect to NDB properly. The physical
  // table in NDB may be extended to support new functionality but should still
  // be possible to use.
  constexpr uint8 legacy_metadata[418] = {
      0x01, 0x00, 0x00, 0x00, 0x6a, 0x22, 0x00, 0x00, 0x96, 0x01, 0x00, 0x00,
      0x78, 0x9c, 0xed, 0xd8, 0x3d, 0x4b, 0xc3, 0x50, 0x14, 0x06, 0xe0, 0x37,
      0x89, 0x89, 0x37, 0xb1, 0xd4, 0x0f, 0x82, 0x83, 0xd3, 0x75, 0x10, 0xb4,
      0x83, 0x6d, 0x45, 0xdd, 0xa4, 0xa6, 0x28, 0x5a, 0xfc, 0x2a, 0xa5, 0x83,
      0x9d, 0xc4, 0x36, 0x01, 0xeb, 0x47, 0xab, 0xad, 0x0a, 0x0e, 0x4a, 0xfd,
      0x29, 0xce, 0x0e, 0x8e, 0x0e, 0x0e, 0x42, 0x07, 0x7f, 0x88, 0xbf, 0x43,
      0x7a, 0x3d, 0x89, 0x55, 0x3a, 0xba, 0x45, 0xf0, 0x3c, 0x4b, 0xce, 0x79,
      0x39, 0xe1, 0xde, 0x33, 0x26, 0x3d, 0xcd, 0x49, 0x1a, 0xc0, 0x98, 0x06,
      0x64, 0x80, 0xba, 0xd6, 0xc5, 0x0f, 0x3d, 0x05, 0x1b, 0x30, 0xc3, 0x52,
      0x7c, 0x67, 0x75, 0x9a, 0x9b, 0x79, 0x03, 0xf6, 0xa3, 0x2e, 0x09, 0xa4,
      0xd3, 0x80, 0x04, 0x63, 0x8c, 0x31, 0xc6, 0x18, 0x63, 0x8c, 0x31, 0xc6,
      0xfe, 0x32, 0x4d, 0x07, 0x1c, 0x7a, 0xde, 0x41, 0x37, 0xa8, 0xeb, 0xd0,
      0xf7, 0xbd, 0xb6, 0x9a, 0x83, 0xde, 0xf1, 0xbe, 0x0a, 0x55, 0x2c, 0x15,
      0x76, 0xbc, 0x52, 0x45, 0xc5, 0x7d, 0x51, 0x16, 0x3f, 0x07, 0x0d, 0xbf,
      0x5a, 0x3b, 0xbd, 0x6a, 0x5f, 0x06, 0xad, 0x79, 0xea, 0x65, 0xd1, 0x2b,
      0x95, 0x0b, 0xe5, 0xc2, 0xde, 0xae, 0xcc, 0x57, 0xe4, 0xd6, 0x7a, 0x45,
      0xa6, 0x53, 0xd3, 0x4b, 0x99, 0xe5, 0x6c, 0x56, 0x7a, 0xdb, 0x1b, 0x7b,
      0xa5, 0x42, 0x79, 0x73, 0x47, 0xae, 0xc8, 0x05, 0x99, 0x4a, 0xcb, 0xd9,
      0x39, 0x68, 0x13, 0x71, 0x2f, 0xc0, 0x18, 0x63, 0x8c, 0x31, 0xc6, 0x18,
      0x63, 0xff, 0xd7, 0xb1, 0x8e, 0xb1, 0xb8, 0xef, 0x10, 0x27, 0x0d, 0x36,
      0x6e, 0xf1, 0x4e, 0x55, 0x17, 0x8b, 0x3f, 0x69, 0x11, 0x93, 0xfd, 0xea,
      0x16, 0x8e, 0xad, 0xbb, 0x73, 0xf2, 0x97, 0x30, 0x04, 0xc3, 0xaf, 0xc2,
      0x84, 0xd9, 0x38, 0x3c, 0x0b, 0x60, 0xc1, 0x6a, 0x9f, 0x36, 0x6b, 0x27,
      0x18, 0x86, 0x75, 0x71, 0x15, 0xb4, 0x6e, 0x20, 0x20, 0x1a, 0x4d, 0x3f,
      0x38, 0xa8, 0xfb, 0x74, 0xb0, 0x15, 0x9c, 0x37, 0x6b, 0x47, 0xf4, 0x59,
      0x6d, 0x50, 0x3b, 0x02, 0x71, 0x1d, 0xb4, 0xda, 0xf5, 0x66, 0x03, 0x09,
      0x98, 0x97, 0x37, 0xe7, 0x01, 0x86, 0x8c, 0x5c, 0x0e, 0xd1, 0x1f, 0x19,
      0xba, 0xc9, 0x68, 0x0e, 0x30, 0x4d, 0x0a, 0xbc, 0x81, 0xc0, 0xb2, 0xe8,
      0xcc, 0xfb, 0x7e, 0xd0, 0xa3, 0x60, 0xd8, 0x12, 0x02, 0x0f, 0xc0, 0xf8,
      0x9a, 0x0b, 0x7c, 0x50, 0x20, 0x84, 0xe3, 0xe0, 0x11, 0x98, 0x0a, 0x27,
      0x0c, 0x01, 0xd8, 0x96, 0xeb, 0xe2, 0x09, 0xc8, 0x87, 0x01, 0x0d, 0xc3,
      0x31, 0x68, 0xe2, 0x79, 0x60, 0x62, 0x24, 0x7c, 0xe5, 0x65, 0x20, 0x48,
      0x98, 0x14, 0xbc, 0x0e, 0x04, 0xca, 0xaf, 0xaa, 0x70, 0x41, 0x15, 0x6d,
      0xa7, 0xa2, 0xd5, 0x54, 0x7f, 0x2f, 0x15, 0x2d, 0xa5, 0xa8, 0xe8, 0xaf,
      0xa3, 0xc2, 0x5d, 0x14, 0x3e, 0x01, 0x4d, 0x53, 0x5e, 0x81};
  if (new_table.setFrm(legacy_metadata, sizeof(legacy_metadata)) != 0) {
    push_warning("Failed to set legacy metadata");
    return false;
  }

  new_table.setForceVarPart(true);

  // Allow table to be read+write also in single user mode
  new_table.setSingleUserMode(NdbDictionary::Table::SingleUserModeReadWrite);

  // The length of "db" and "name" was adjusted in 8.0.18 to allow
  // passing 255 bytes long identifiers
  int db_and_name_length = IDENTIFIER_LENGTH;
  if (mysql_version < 80018) {
    // Use legacy identifier length when creating the table for
    // backwards compatibility testing
    db_and_name_length = LEGACY_IDENTIFIER_LENGTH;
  }

  {
    // db VARBINARY(255) NOT NULL
    NdbDictionary::Column col_db(COL_DB);
    col_db.setType(NdbDictionary::Column::Varbinary);
    col_db.setLength(db_and_name_length);
    col_db.setNullable(false);
    col_db.setPrimaryKey(true);
    if (!define_table_add_column(new_table, col_db)) return false;
  }

  {
    // name VARBINARY(255) NOT NULL
    NdbDictionary::Column col_name(COL_NAME);
    col_name.setType(NdbDictionary::Column::Varbinary);
    col_name.setLength(db_and_name_length);
    col_name.setNullable(false);
    col_name.setPrimaryKey(true);
    if (!define_table_add_column(new_table, col_name)) return false;
  }

  {
    // slock BINARY(32) NOT NULL
    NdbDictionary::Column col_slock(COL_SLOCK);
    col_slock.setType(NdbDictionary::Column::Binary);
    col_slock.setLength(32);
    col_slock.setNullable(false);
    if (!define_table_add_column(new_table, col_slock)) return false;
  }

  {
    // query BLOB NOT NULL
    NdbDictionary::Column col_query(COL_QUERY);
    col_query.setType(NdbDictionary::Column::Blob);
    col_query.setInlineSize(256);
    col_query.setPartSize(2000);
    col_query.setStripeSize(0);
    col_query.setNullable(false);
    if (!define_table_add_column(new_table, col_query)) return false;
  }

  {
    // node_id INT UNSIGNED NOT NULL
    NdbDictionary::Column col_nodeid(COL_NODEID);
    col_nodeid.setType(NdbDictionary::Column::Unsigned);
    col_nodeid.setNullable(false);
    if (!define_table_add_column(new_table, col_nodeid)) return false;
  }

  {
    // epoch BIGINT UNSIGNED NOT NULL
    NdbDictionary::Column col_epoch(COL_EPOCH);
    col_epoch.setType(NdbDictionary::Column::Bigunsigned);
    col_epoch.setNullable(false);
    if (!define_table_add_column(new_table, col_epoch)) return false;
  }

  {
    // id INT UNSIGNED NOT NULL
    NdbDictionary::Column col_id(COL_ID);
    col_id.setType(NdbDictionary::Column::Unsigned);
    col_id.setNullable(false);
    if (!define_table_add_column(new_table, col_id)) return false;
  }

  {
    // version INT UNSIGNED NOT NULL
    NdbDictionary::Column col_version(COL_VERSION);
    col_version.setType(NdbDictionary::Column::Unsigned);
    col_version.setNullable(false);
    if (!define_table_add_column(new_table, col_version)) return false;
  }

  {
    // type INT UNSIGNED NOT NULL
    NdbDictionary::Column col_type(COL_TYPE);
    col_type.setType(NdbDictionary::Column::Unsigned);
    col_type.setNullable(false);
    if (!define_table_add_column(new_table, col_type)) return false;
  }

  if (mysql_version >= 80017) {
    // schema_op_id INT UNSIGNED NULL
    NdbDictionary::Column col_schema_op_id(COL_SCHEMA_OP_ID);
    col_schema_op_id.setType(NdbDictionary::Column::Unsigned);
    col_schema_op_id.setNullable(true);  // NULL!
    if (!define_table_add_column(new_table, col_schema_op_id)) return false;
  }

  return true;
}

bool Ndb_schema_dist_table::need_upgrade() const {
  // Check that 'schema_op_id' column exists. If exists, it's used for sending
  // the schema_op_id from client to participants who can then use it when
  // replying using ndb_schema_result (if they support that table)
  if (!have_schema_op_id_column()) {
    return true;
  }
  // The 'db' and 'name' column need to be upgrade if length is shorter than
  // current identifier length
  if (get_column_max_length(COL_DB) < IDENTIFIER_LENGTH ||
      get_column_max_length(COL_NAME) < IDENTIFIER_LENGTH) {
    return true;
  }
  return false;
}

bool Ndb_schema_dist_table::drop_events_in_NDB() const {
  // Drop the default event on ndb_schema table
  if (!drop_event_in_NDB("REPL$mysql/ndb_schema")) return false;

  // Legacy event on ndb_schema table, drop since it might
  // have been created(although ages ago)
  if (!drop_event_in_NDB("REPLF$mysql/ndb_schema")) return false;

  return true;
}

std::string Ndb_schema_dist_table::define_table_dd() const {
  std::stringstream ss;
  ss << "CREATE TABLE " << db_name() << "." << table_name() << "(\n";
  ss << "db VARBINARY(" << get_column_max_length(COL_DB) << ") NOT NULL,";
  ss << "name VARBINARY(" << get_column_max_length(COL_NAME) << ") NOT NULL,";
  ss << "slock BINARY(32) NOT NULL,"
        "query BLOB NOT NULL,"
        "node_id INT UNSIGNED NOT NULL,"
        "epoch BIGINT UNSIGNED NOT NULL,"
        "id INT UNSIGNED NOT NULL,"
        "version INT UNSIGNED NOT NULL,"
        "type INT UNSIGNED NOT NULL,";
  if (have_schema_op_id_column()) {
    ss << "schema_op_id INT UNSIGNED NULL,";
  }
  ss << "PRIMARY KEY USING HASH (db,name)"
     << ") ENGINE=ndbcluster CHARACTER SET latin1";
  return ss.str();
}

int Ndb_schema_dist_table::get_slock_bytes() const {
  return get_column_max_length(COL_SLOCK);
}

bool Ndb_schema_dist_table::have_schema_op_id_column() const {
  const NdbDictionary::Table *ndb_tab = get_table();
  return ndb_tab->getColumn(COL_SCHEMA_OP_ID);
}

// Helper functions to read and write properties into the query column of
// the schema UUID tuple. The properties are written in the form of
// "key1=value1;key2=value2;"
static std::string map_extract_key_value_string(
    const std::map<std::string, std::string> &kv_map) {
  std::string key_value_str;
  std::for_each(kv_map.begin(), kv_map.end(),
                [&](std::pair<std::string, std::string> entry) -> void {
                  key_value_str.append(entry.first);
                  key_value_str.append("=");
                  key_value_str.append(entry.second);
                  key_value_str.append(";");
                });
  return key_value_str;
}

static std::string key_value_str_get_value(const std::string &kv_str,
                                           const char *key) {
  std::istringstream kv_ss(kv_str);
  std::string kv_pair;
  while (std::getline(kv_ss, kv_pair, ';')) {
    int key_length = kv_pair.find('=');
    DBUG_ASSERT(key_length > 0);
    if (kv_pair.substr(0, key_length).compare(key) == 0) {
      return kv_pair.substr(key_length + 1);
    }
  }
  return "";
}

bool Ndb_schema_dist_table::get_schema_uuid(std::string *schema_uuid) const {
  DBUG_TRACE;
  const NdbDictionary::Table *ndb_table = get_table();

  // Pack the table and db names to be used during read into table
  char db_name_buf[FN_REFLEN];
  char table_name_buf[FN_REFLEN];
  pack_varbinary(COL_DB, DB_NAME.c_str(), db_name_buf);
  pack_varbinary(COL_NAME, TABLE_NAME.c_str(), table_name_buf);
  std::string query_col_value;

  // Lambda read function to execute using ndb_trans_retry()
  std::function<const NdbError *(NdbTransaction *)> read_ndb_schema_func =
      [&](NdbTransaction *trans) -> const NdbError * {
    DBUG_TRACE;
    NdbOperation *read_op = trans->getNdbOperation(ndb_table);
    if (read_op == nullptr) return &trans->getNdbError();

    // Define read operation based on 'db_name, table_name' key
    if (read_op->readTuple() != 0 || read_op->equal(COL_DB, db_name_buf) != 0 ||
        read_op->equal(COL_NAME, table_name_buf) != 0) {
      return &read_op->getNdbError();
    }

    // Setup read for the query column value.
    NdbBlob *query_blob_handle = read_op->getBlobHandle(COL_QUERY);
    if (!query_blob_handle) {
      return &read_op->getNdbError();
    }

    if (trans->execute(NdbTransaction::NoCommit,
                       NdbOperation::DefaultAbortOption,
                       1 /* force send */) != 0) {
      // Execute failed.
      return &trans->getNdbError();
    }

    // Transaction execute succeeded. Check the operation for errors
    const NdbError &read_op_error = read_op->getNdbError();
    if (read_op_error.code == 0) {
      // The tuple exists. Read the value from query blob and return
      if (!unpack_blob_not_null(query_blob_handle, &query_col_value)) {
        return &query_blob_handle->getNdbError();
      }
      return nullptr;
    } else if (read_op_error.classification ==
               NdbError::Classification::NoDataFound) {
      // The tuple doesn't exist.
      ndb_log_verbose(19, "The schema UUID tuple doesn't exist");
      return nullptr;
    } else {
      // Operation failed with an unexpected error
      return &read_op_error;
    }
  };

  NdbError ndb_err;
  if (!ndb_trans_retry(get_ndb(), get_thd(), ndb_err, read_ndb_schema_func)) {
    push_warning("Failed to read the schema UUID tuple: %s(%d).",
                 ndb_err.message, ndb_err.code);
    return false;
  }

  if (query_col_value.size() == 0) {
    // Schema UUID is not present
    ndb_log_info("Schema UUID not present in ndb_schema table");
    return true;
  }

  // The tuple with Schema UUID exists. It is stored as a key value
  // pair of form "schema_uuid=<UUID>;". Extract the value and return.
  schema_uuid->assign(
      key_value_str_get_value(query_col_value, SCHEMA_UUID_KEY));
  DBUG_ASSERT(schema_uuid->size() == UUID_LENGTH);
  ndb_log_verbose(19, "Schema UUID read from NDB : %s", schema_uuid->c_str());
  return true;
}

bool Ndb_schema_dist_table::update_schema_uuid_in_NDB(
    const std::string &schema_uuid) const {
  DBUG_TRACE;

  const NdbDictionary::Table *ndb_table = get_table();
  DBUG_ASSERT(ndb_table != nullptr);

  // Store the UUID as a key value pair of form "schema_uuid=<UUID>;"
  std::map<std::string, std::string> ndb_schema_props;
  ndb_schema_props.insert({SCHEMA_UUID_KEY, schema_uuid.c_str()});
  const std::string ndb_schema_props_str =
      map_extract_key_value_string(ndb_schema_props);

  // Pack db and table_name
  char db_buf[FN_REFLEN];
  char name_buf[FN_REFLEN];
  pack_varbinary(COL_DB, DB_NAME.c_str(), db_buf);
  pack_varbinary(COL_NAME, TABLE_NAME.c_str(), name_buf);

  // Function for writing row to ndb_schema
  std::function<const NdbError *(NdbTransaction *)> write_schema_op_func =
      [&](NdbTransaction *trans) -> const NdbError * {
    DBUG_TRACE;

    NdbOperation *op = trans->getNdbOperation(ndb_table);
    if (op == nullptr) return &trans->getNdbError();

    // Buffer with zeroes for slock
    std::vector<char> slock_zeroes;
    slock_zeroes.assign(get_slock_bytes(), 0);
    const char *slock_buf = slock_zeroes.data();

    const Uint64 log_epoch = 0;
    if (op->writeTuple() != 0 || op->equal(COL_DB, db_buf) != 0 ||
        op->equal(COL_NAME, name_buf) != 0 ||
        op->setValue(COL_SLOCK, slock_buf) != 0 ||
        op->setValue(COL_NODEID, 0) != 0 ||
        op->setValue(COL_EPOCH, log_epoch) != 0 ||
        op->setValue(COL_ID, 0) != 0 || op->setValue(COL_VERSION, 0) != 0 ||
        op->setValue(COL_TYPE, SOT_CREATE_TABLE) != 0 ||
        op->setAnyValue(0) != 0)
      return &op->getNdbError();

    if (have_schema_op_id_column() && op->setValue(COL_SCHEMA_OP_ID, 0) != 0)
      return &op->getNdbError();

    NdbBlob *ndb_blob = op->getBlobHandle(COL_QUERY);
    if (ndb_blob == nullptr) return &op->getNdbError();

    if (ndb_blob->setValue(ndb_schema_props_str.c_str(),
                           ndb_schema_props_str.length()) != 0)
      return &ndb_blob->getNdbError();

    if (trans->execute(NdbTransaction::Commit, NdbOperation::DefaultAbortOption,
                       1 /* force send */) != 0) {
      return &trans->getNdbError();
    }

    return nullptr;
  };

  NdbError ndb_err;
  if (!ndb_trans_retry(get_ndb(), get_thd(), ndb_err, write_schema_op_func)) {
    push_warning(
        "Failed to update schema UUID in 'mysql.ndb_schema' table. Code : %d. "
        "Error : %s",
        ndb_err.code, ndb_err.message);
    return false;
  }

  return true;
}

bool Ndb_schema_dist_table::pre_upgrade() const {
  // During upgrade, the schema UUID need not be regenerated.
  // Save it for restoring it later after upgrade
  if (!get_schema_uuid(&old_ndb_schema_uuid)) return false;
  return true;
}

bool Ndb_schema_dist_table::post_install() const {
  DBUG_TRACE;

  std::string schema_uuid;
  if (old_ndb_schema_uuid.empty()) {
    // The table was just created
    // Generate a new schema uuid for the table
    String schema_uuid_buf;
    mysql_generate_uuid(&schema_uuid_buf);
    schema_uuid.assign(schema_uuid_buf.ptr(), schema_uuid_buf.length());
    ndb_log_verbose(19, "Generated new schema UUID : %s", schema_uuid.c_str());
  } else {
    // The table was just upgraded
    // Restore the old schema UUID
    schema_uuid = std::move(old_ndb_schema_uuid);
    ndb_log_verbose(19, "Restoring schema UUID : %s after upgrade",
                    schema_uuid.c_str());
  }

  // Update the UUID in the ndb_schema_table
  if (!update_schema_uuid_in_NDB(schema_uuid)) {
    return false;
  }
  return true;
}