Safest way to add primary key to table

I created a table without a primary key and an UPDATE statement caused the cluster to lock up due to this issue [URL]https://www.percona.com/blog/2013/10/18/innodb-scalability-issues-tables-without-primary-keys/[/URL]

My question is, what’s the best way to add a primary key to this table:

  1. Use an ALTER table statement.
  2. TRUNCATE table, then issue an ALTER statement to add the primary key and then INSERT rows.
  3. DROP table and then issue a CREATE table with a primary key then INSERT rows.

I don’t want to lock the cluster up again.

The table in questions has about 50k rows and is 10MB in size.

Could you just update with the versions and environment information?

We have a Percona XtraDB Cluster of 3 nodes, all running version 5.6.24. The OS on each node is CentOS 6, 4GB RAM, Intel(R) Xeon™ CPU 2.80GHz (dual core).

The result of a SHOW GLOBAL VARIABLES; statement is as follows (split over 2 posts):

Variable_name;Value
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auto_increment_offset;2
autocommit;ON
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back_log;80
basedir;/usr
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bind_address;*
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character_set_results;latin1
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character_sets_dir;/usr/share/percona-xtradb-cluster/charsets/
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csv_mode;
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eb55dadf-db4d-11e5-ae62-0011259dcb16:1-4193930
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gtid_owned;aecfffa4-55b2-ee1a-5417-31ed7d9e97c3:61403833#14885144:61966645#15068932:61973098#15063624:62677904#15298043:61839513#15034335:61954783#15065496:61956753#15067169:62216955#15137921:61967200#15068932:61973079#15063624:61973095#15063624:61483418#14899277:61973112#15063624:61973114#15063624:61973680#15063624:62751587#15306881:62199223#15135974:62187813#15134559:62420886#15197500:61483772#14899277
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eb55dadf-db4d-11e5-ae62-0011259dcb16:1-4193930
have_backup_locks;YES
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ignore_db_dirs;
init_connect;
init_file;
init_slave;
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innodb_stats_sample_pages;8
innodb_stats_transient_sample_pages;8
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innodb_support_xa;ON
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lc_messages;en_US
lc_messages_dir;/usr/share/percona-xtradb-cluster/
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optimizer_switch;index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,subquery_materialization_cost_based=on,use_index_extensions=on
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performance_schema;ON
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performance_schema_users_size;100
pid_file;/var/lib/mysql/database01.pid
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relay_log;
relay_log_basename;
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slave_type_conversions;
slow_launch_time;2
slow_query_log;ON
slow_query_log_always_write_time;10.000000
slow_query_log_file;/var/log/slow.log
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slow_query_log_timestamp_precision;second
slow_query_log_use_global_control;
socket;/var/lib/mysql/mysql.sock
sort_buffer_size;262144
sql_auto_is_null;OFF
sql_big_selects;ON
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sql_quote_show_create;ON
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ssl_ca;
ssl_capath;
ssl_cert;
ssl_cipher;
ssl_crl;
ssl_crlpath;
ssl_key;
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table_open_cache;2000
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thread_handling;one-thread-per-connection
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thread_statistics;OFF
time_format;%H:%i:%s
time_zone;SYSTEM
timed_mutexes;OFF
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tmpdir;/tmp
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transaction_prealloc_size;4096
tx_isolation;REPEATABLE-READ
tx_read_only;OFF
unique_checks;ON
updatable_views_with_limit;YES
userstat;OFF
version;5.6.24-72.2-56-log
version_comment;Percona XtraDB Cluster (GPL), Release rel72.2, Revision 1, WSREP version 25.11, wsrep_25.11
version_compile_machine;x86_64
version_compile_os;Linux
wait_timeout;28800
wsrep_OSU_method;TOI
wsrep_auto_increment_control;ON
wsrep_causal_reads;OFF
wsrep_certify_nonPK;ON
wsrep_cluster_address;gcomm://[CLUSTER IP’S HERE]
wsrep_cluster_name;my_wsrep_cluster
wsrep_convert_LOCK_to_trx;OFF
wsrep_data_home_dir;/var/lib/mysql/
wsrep_dbug_option;
wsrep_debug;OFF
wsrep_desync;OFF
wsrep_drupal_282555_workaround;OFF
wsrep_forced_binlog_format;NONE
wsrep_load_data_splitting;ON
wsrep_log_conflicts;OFF
wsrep_max_ws_rows;131072
wsrep_max_ws_size;1073741824
wsrep_mysql_replication_bundle;0
wsrep_node_address;
wsrep_node_incoming_address;AUTO
wsrep_node_name;database01
wsrep_notify_cmd;
wsrep_on;ON
wsrep_preordered;OFF
wsrep_provider;/usr/lib64/libgalera_smm.so
wsrep_provider_options;base_dir = /var/lib/mysql/; base_host = [ip here]; base_port = 4567; cert.log_conflicts = no; debug = no; evs.auto_evict = 0; evs.causal_keepalive_period = PT1S; evs.debug_log_mask = 0x1; evs.delay_margin = PT1S; evs.delayed_keep_period = PT30S; evs.inactive_check_period = PT0.5S; evs.inactive_timeout = PT15S; evs.info_log_mask = 0; evs.install_timeout = PT7.5S; evs.join_retrans_period = PT1S; evs.keepalive_period = PT1S; evs.max_install_timeouts = 3; evs.send_window = 4; evs.stats_report_period = PT1M; evs.suspect_timeout = PT5S; evs.use_aggregate = true; evs.user_send_window = 2; evs.version = 0; evs.view_forget_timeout = P1D; gcache.dir = /var/lib/mysql/; gcache.keep_pages_size = 0; gcache.mem_size = 0; gcache.name = /var/lib/mysql//galera.cache; gcache.page_size = 128M; gcache.size = 128M; gcs.fc_debug = 0; gcs.fc_factor = 1.0; gcs.fc_limit = 16; gcs.fc_master_slave = no; gcs.max_packet_size = 64500; gcs.max_throttle = 0.25; gcs.recv_q_hard_limit = 9223372036854775807; gcs.recv_q_soft_limit = 0.25; gcs.sync_donor = no; gmcast.listen_addr = tcp://0.0.0.0:4567; gmcast.mcast_addr = ; gmcast.mcast_ttl = 1; gmcast.peer_timeout = PT3S; gmcast.segment = 0; gmcast.time_wait = PT5S; gmcast.version = 0; ist.recv_addr = [ip here]; pc.announce_timeout = PT3S; pc.checksum = false; pc.ignore_quorum = false; pc.ignore_sb = false; pc.linger = PT20S; pc.npvo = false; pc.recovery = true; pc.version = 0; pc.wait_prim = true; pc.wait_prim_timeout = P30S; pc.weight = 1; protonet.backend = asio; protonet.version = 0; repl.causal_read_timeout = PT30S; repl.commit_order = 3; repl.key_format = FLAT8; repl.max_ws_size = 2147483647; repl.proto_max = 7; socket.checksum = 2;
wsrep_recover;OFF
wsrep_reject_queries;NONE
wsrep_replicate_myisam;OFF
wsrep_restart_slave;OFF
wsrep_retry_autocommit;1
wsrep_slave_FK_checks;ON
wsrep_slave_UK_checks;OFF
wsrep_slave_threads;1
wsrep_sst_auth;********
wsrep_sst_donor;
wsrep_sst_donor_rejects_queries;OFF
wsrep_sst_method;xtrabackup-v2
wsrep_sst_receive_address;AUTO
wsrep_start_position;5130005b-aa4d-11e5-abe8-ce128261683c:5420391
wsrep_sync_wait;0

  1. Yes. ALTER TABLE foo ADD PRIMARY KEY(existingColumn);
    You may need to add a new column if you do not already have a column that can be used as PRIMARY KEY. Simplest is to just add a INT UNSIGNED AUTO_INCREMENT column and make that your primary key.