[MDEV-17873] MyRocks-Gap-Lock: lock wait doesn't set correct STATE Created: 2018-11-29  Updated: 2021-02-15

Status: Open
Project: MariaDB Server
Component/s: OTHER
Affects Version/s: N/A
Fix Version/s: 10.2

Type: Bug Priority: Major
Reporter: Sergei Petrunia Assignee: Sergei Petrunia
Resolution: Unresolved Votes: 0
Labels: None

Issue Links:
PartOf
is part of MDEV-15603 Gap Lock support in MyRocks Stalled

 Description   

When a query is waiting for row lock, it does not have waiting for row lock status in I_S.PROCESSLIST.

This is a property of TokuDB, as well. Example of a TokuDB query waiting for a row lock: 

             ID: 8
 
           USER: root
 
           HOST: localhost
 
             DB: test
 
        COMMAND: Query
 
           TIME: 3
 
          STATE: Statistics
 
           INFO: select * from t1 where pk=1 for update
 
        TIME_MS: 3683.455
 
          STAGE: 0
 
      MAX_STAGE: 0
 
       PROGRESS: 0.000
 
    MEMORY_USED: 78480
 
MAX_MEMORY_USED: 80488
 
  EXAMINED_ROWS: 0
 
       QUERY_ID: 20
 
    INFO_BINARY: select * from t1 where pk=1 for update
 
            TID: 30172



 Comments   
Comment by Sergei Petrunia [ 2018-11-29 ]

It's the same in Percona Server

mysql> select * from information_schema.processlist\G
 
*************************** 1. row ***************************
 
           ID: 3
 
         USER: root
 
         HOST: localhost
 
           DB: test
 
      COMMAND: Query
 
         TIME: 6
 
        STATE: statistics
 
         INFO: select * from t10 where pk=2 for update
 
      TIME_MS: 6724
 
    ROWS_SENT: 0
 
ROWS_EXAMINED: 0

Comment by Sergei Petrunia [ 2019-01-03 ]

Well, one can observe TokuDB lock waits with tokudb_lock_waits table:

MariaDB [j1]> select * from information_schema.TokuDB_lock_waits\G
 
*************************** 1. row ***************************
 
               requesting_trx_id: 95
 
                 blocking_trx_id: 93
 
                lock_waits_dname: ./j1/t10-main
 
             lock_waits_key_left: ff01000000
 
            lock_waits_key_right: 0101000000
 
           lock_waits_start_time: 1546543046850
 
         lock_waits_table_schema: j1
 
           lock_waits_table_name: t10
 
lock_waits_table_dictionary_name: main

There is also TokuDB_trx table which maps Toku's transaction id to mysql connection id:

MariaDB [j1]> select * from information_schema.TokuDB_trx\G
 
*************************** 1. row ***************************
 
             trx_id: 93
 
trx_mysql_thread_id: 10
 
           trx_time: 435
 
*************************** 2. row ***************************
 
             trx_id: 95
 
trx_mysql_thread_id: 11
 
           trx_time: 314
 
2 rows in set (0.002 sec)

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