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  1. MariaDB Server
  2. MDEV-34427

BNL-H has not optimal implementation for varchar type

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Details

    • Bug
    • Status: Open (View Workflow)
    • Major
    • Resolution: Unresolved
    • 10.5, 10.6, 10.11, 11.1(EOL), 11.2(EOL), 11.4, 11.5(EOL), 11.6(EOL)
    • 11.6(EOL)
    • Optimizer
    • None

    Description

      BNL-H has not optimal implementation for varchar type. The query execution time increases in direct proportion with increasing size of varchar for the same data.

      Example:

      CREATE OR REPLACE TABLE t1(col1 VARCHAR(500)) engine=INNODB character set latin1 collate latin1_swedish_ci;
      		 
      CREATE OR REPLACE TABLE t2(col2 VARCHAR(500)) engine=INNODB character set latin1 collate latin1_swedish_ci;
      		 
      insert into t1 select  FLOOR(1 + (RAND() * 200000)) from seq_1_to_20000;
      		 
      insert into t2 select  FLOOR(1 + (RAND() * 20000))  from seq_1_to_20000;
      		 
      set join_cache_level=3;
      		 
      select max(A.col1) from t1 A, t2 B where A.col1=B.col2;

      Time execution: 0.204 sec

      CREATE OR REPLACE TABLE t1(col1 VARCHAR(2000)) engine=INNODB character set latin1 collate latin1_swedish_ci;
      		 
      CREATE OR REPLACE TABLE t2(col2 VARCHAR(2000)) engine=INNODB character set latin1 collate latin1_swedish_ci;
      		 
      insert into t1 select  FLOOR(1 + (RAND() * 200000)) from seq_1_to_20000;
      		 
      insert into t2 select  FLOOR(1 + (RAND() * 20000))  from seq_1_to_20000;
      		 
      set join_cache_level=3;
      		 
      select max(A.col1) from t1 A, t2 B where A.col1=B.col2;

      Time execution: 0.793 sec

      Attachments

        Issue Links

          is duplicated by

          Bug - A problem which impairs or prevents the functions of the product. MDEV-34352 Execution time for Block Nested Loop Hash (BNLH) join with charset utf8mb4 is 7-20 times slower than with latin1

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-34352 Execution time for Block Nested Loop Hash (BNLH) join with charset utf8mb4 is 7-20 times slower than with latin1

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Task - A task that needs to be done. MDEV-34232 Check performance of BNL-H vs MySQL's hash join

          • Major - Major loss of function.
          • Open

          Bug - A problem which impairs or prevents the functions of the product. MDEV-34417 Wrong result set with utf8mb4_danish_ci and BNLH join

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Activity

            People

              psergei Sergei Petrunia
              lstartseva Lena Startseva
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              Dates

                Created:
                Updated:

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