COUNT(*) vs COUNT(1) in MySQL

count-asterisk-vs-count-1-mysql.sql

-- Copyright Data Geekery GmbH
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--     http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
--
CREATE TABLE t (i INT);

INSERT INTO t 
WITH RECURSIVE d (i) AS (
  SELECT 1
  UNION ALL
  SELECT i + 1
  FROM d
  WHERE i < 1000
)
SELECT row_number() OVER (ORDER BY (SELECT 1)) FROM d AS d1, d AS d2;



CREATE TABLE IF NOT EXISTS print_relative (run INT, stmt INT, elapsed BIGINT);

delimiter //

CREATE PROCEDURE benchmark ()
BEGIN
  DECLARE done INT DEFAULT FALSE;
  DECLARE v_ts BIGINT;
  DECLARE v_repeat INT DEFAULT 100;
  DECLARE r, c INT;
  DECLARE a INT;

  DECLARE cur1 CURSOR FOR 
    SELECT COUNT(*) FROM t;
    
  DECLARE cur2 CURSOR FOR 
    SELECT COUNT(1) FROM t;

  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
  
  SET r = 0;
  
  REPEAT
    SET v_ts = ROUND(UNIX_TIMESTAMP(CURTIME(4)) * 1000);
    SET c = 0;
    REPEAT
      OPEN cur1;
	  
      read_loop: LOOP
        FETCH cur1 INTO a;
        IF done THEN
          LEAVE read_loop;
        END IF;
	  END LOOP;
      
      CLOSE cur1;
      SET c = c + 1;
    UNTIL c >= v_repeat END REPEAT;
    
    INSERT INTO print_relative VALUES (r, 1, ROUND(UNIX_TIMESTAMP(CURTIME(4)) * 1000) - v_ts);
    
    SET v_ts = ROUND(UNIX_TIMESTAMP(CURTIME(4)) * 1000);
    SET c = 0;
    REPEAT
      OPEN cur2;
	  
      read_loop: LOOP
        FETCH cur2 INTO a;
        IF done THEN
          LEAVE read_loop;
        END IF;
	  END LOOP;
      
      CLOSE cur2;
      SET c = c + 1;
    UNTIL c >= v_repeat END REPEAT;
    
    INSERT INTO print_relative VALUES (r, 2, ROUND(UNIX_TIMESTAMP(CURTIME(4)) * 1000) - v_ts);

    SET r = r + 1;
  UNTIL r >= 5 END REPEAT;
END//

delimiter ;

CALL benchmark();

SELECT
  run, 
  stmt,
  CAST(elapsed / MIN(elapsed) OVER() AS DECIMAL(20, 4)) ratio,
  '                                            ' `Copyright Data Geekery GmbH`
FROM print_relative
UNION ALL 
SELECT null, null, null, null
UNION ALL
SELECT null, null, null, 'Copyright Data Geekery GmbH'
UNION ALL
SELECT null, null, null, 'https://www.jooq.org/benchmark';


DROP PROCEDURE benchmark;

DROP TABLE print_relative;

DROP TABLE t;