如何批量更新postgres中的一列5500万条记录

Question

我想更新postgres表的一列。记录大约有5500万条，所以我们需要在10000条记录中更新它。注意：我们要更新所有行。但我们不想锁桌子。

我正在尝试以下查询-

Update account set name = Some name where id between 1 and 10000

我们如何为每10000条记录更新做一个循环？

如有任何建议和帮助，将不胜感激。

PostgreSQL 10.5

Answer 1

设置测试环境：

DROP TABLE IF EXISTS account;
CREATE TABLE account(id integer, name text);

INSERT INTO account
VALUES (1, 'jonas'),(10002, 'petras');

更新脚本：

DO $$
DECLARE
  _id integer;
  _min_id integer;
  _max_id integer; 
  _batch_size integer = 10000;
BEGIN
  SELECT 
    MIN(id),
    MAX(id)
  INTO
    _min_id,
    _max_id
  FROM
    account;

  _id := _min_id;

  LOOP
    UPDATE account SET
      name = 'Some name' 
    WHERE id >=_id 
      AND id < _id + _batch_size;

    COMMIT;

    _id := _id + _batch_size;
    IF _id > _max_id THEN
      EXIT;
    END IF;
  END LOOP;
END;
$$;

Answer 2

您可以使用一个过程（从版本11开始提供）并逐个执行，如下所示：

CREATE or replace PROCEDURE do_update()
LANGUAGE plpgsql
AS $$
BEGIN
    FOR i IN 1..55000000 -- 55 million, or whatever number you need
    LOOP 

        Update account set name = Some name where id = i;
        COMMIT;
        
        RAISE INFO 'id: %', i;
    END LOOP;
END;
$$;

CALL do_update();

Answer 3

与其一次提交所有更改（或其他答案中建议的5500万次），我宁愿尝试将更新行拆分为小批量，例如，如您建议的10k条记录。在PL/pgSQL中，可以使用关键字BY以给定步骤迭代集合。因此，您可以在匿名代码块中执行批更新，如下所示：

DO $$ 
DECLARE 
  page int := 10000;
  min_id bigint; max_id bigint;
BEGIN
  SELECT max(id),min(id) INTO max_id,min_id FROM account;
  FOR j IN min_id..max_id BY page LOOP 
    UPDATE account SET name = 'your magic goes here'
    WHERE id >= j AND id < j+page;
    COMMIT;            
  END LOOP;
END; $$;

• 您可能需要调整WHERE子句以避免不必要的重叠。

带有顺序id的1051行的数据样本：

CREATE TABLE account (id int, name text);
INSERT INTO account VALUES(generate_series(0,1050),'untouched record..');

正在执行匿名代码块...

DO $$ 
DECLARE 
  page int := 100;
  min_id bigint; max_id bigint;
BEGIN
  SELECT max(id),min(id) INTO max_id,min_id FROM account;
  FOR j IN min_id..max_id BY page LOOP 
    UPDATE account SET name = now() ||' -> UPDATED ' || j  || ' to ' || j+page
    WHERE id >= j AND id < j+page;
    RAISE INFO 'committing data from % to % at %', j,j+page,now();
    COMMIT;            
  END LOOP;
END; $$;
    
INFO:  committing data from 0 to 100 at 2021-04-14 17:35:42.059025+02
INFO:  committing data from 100 to 200 at 2021-04-14 17:35:42.070274+02
INFO:  committing data from 200 to 300 at 2021-04-14 17:35:42.07806+02
INFO:  committing data from 300 to 400 at 2021-04-14 17:35:42.087201+02
INFO:  committing data from 400 to 500 at 2021-04-14 17:35:42.096548+02
INFO:  committing data from 500 to 600 at 2021-04-14 17:35:42.105876+02
INFO:  committing data from 600 to 700 at 2021-04-14 17:35:42.114514+02
INFO:  committing data from 700 to 800 at 2021-04-14 17:35:42.121946+02
INFO:  committing data from 800 to 900 at 2021-04-14 17:35:42.12897+02
INFO:  committing data from 900 to 1000 at 2021-04-14 17:35:42.134388+02
INFO:  committing data from 1000 to 1100 at 2021-04-14 17:35:42.13951+02

...您可以批量更新您的行。为了证明我的观点，以下查询按更新时间对记录进行分组：

SELECT DISTINCT ON (name) name, count(id)
FROM account 
GROUP BY name ORDER BY name;

                         name                         | count 
------------------------------------------------------+-------
 2021-04-14 17:35:42.059025+02 -> UPDATED 0 to 100    |   100
 2021-04-14 17:35:42.070274+02 -> UPDATED 100 to 200  |   100
 2021-04-14 17:35:42.07806+02 -> UPDATED 200 to 300   |   100
 2021-04-14 17:35:42.087201+02 -> UPDATED 300 to 400  |   100
 2021-04-14 17:35:42.096548+02 -> UPDATED 400 to 500  |   100
 2021-04-14 17:35:42.105876+02 -> UPDATED 500 to 600  |   100
 2021-04-14 17:35:42.114514+02 -> UPDATED 600 to 700  |   100
 2021-04-14 17:35:42.121946+02 -> UPDATED 700 to 800  |   100
 2021-04-14 17:35:42.12897+02 -> UPDATED 800 to 900   |   100
 2021-04-14 17:35:42.134388+02 -> UPDATED 900 to 1000 |   100
 2021-04-14 17:35:42.13951+02 -> UPDATED 1000 to 1100 |    51

演示：<代码>数据库