postgresql - Postgres在并发更新中陷入僵局

我们有一个应用程序，它从数据流中读取并将这些信息向上插入数据库。数据是发生在Google云端硬盘上的更改，这意味着影响相同对象的许多事件可能彼此之间非常接近。

将这些信息上传到数据库时，我们陷入了僵局，这是日志中显示的内容。我已经重建并清理了查询的可读性:

ERROR:  deadlock detected
DETAIL:  Process 10586 waits for ShareLock on transaction 166892743; blocked by process 10597.
  Process 10597 waits for ShareLock on transaction 166892741; blocked by process 10586.
  Process 10586:
          INSERT INTO documents
              (version, source, source_id, ingestion_date)
          VALUES
              (0, 'googledrive', 'alpha', '2017-09-21T07:03:51.074Z'),
              (0, 'googledrive', 'beta', '2017-09-21T07:03:51.074Z')
              (0, 'googledrive', 'gamma', '2017-09-21T07:03:51.074Z'),
              (0, 'googledrive', 'delta', '2017-09-21T07:03:51.074Z'),
              (0, 'googledrive', 'epsilon', '2017-09-21T07:03:51.074Z'),
              (0, 'googledrive', 'zeta', '2017-09-21T07:03:51.074Z')

          ON CONFLICT (source, source_id)
          DO UPDATE
          SET
              ingestion_date = EXCLUDED.ingestion_date,
              version = documents.version + 1

          RETURNING source_id, source, uid

  Process 10597:
          INSERT INTO documents
              (version, source, source_id, ingestion_date)
          VALUES
              (0, 'googledrive', 'delta', '2017-09-21T07:03:51.167Z'),
              (0, 'googledrive', 'gamma', '2017-09-21T07:03:51.167Z')

          ON CONFLICT (source, source_id)
          DO UPDATE
          SET
              ingestion_date = EXCLUDED.ingestion_date,
              version = documents.version + 1

          RETURNING source_id, source, uid

HINT:  See server log for query details.
CONTEXT:  while locking tuple (3908269,11) in relation "documents"
STATEMENT:
          INSERT INTO documents
              (version, source, source_id, ingestion_date)
          VALUES
              (0, 'googledrive', 'alpha', '2017-09-21T07:03:51.074Z'),
              (0, 'googledrive', 'beta', '2017-09-21T07:03:51.074Z'),
              (0, 'googledrive', 'gamma', '2017-09-21T07:03:51.074Z'),
              (0, 'googledrive', 'delta', '2017-09-21T07:03:51.074Z'),
              (0, 'googledrive', 'epsilon', '2017-09-21T07:03:51.074Z'),
              (0, 'googledrive', 'zeta', '2017-09-21T07:03:51.074Z')

          ON CONFLICT (source, source_id)
          DO UPDATE
          SET
              ingestion_date = EXCLUDED.ingestion_date,
              version = documents.version + 1

          RETURNING source_id, source, uid

模式:

    Column      |            Type             |                             Modifiers
----------------+-----------------------------+-------------------------------------------------------------------
uid             | uuid                        | not null default gen_random_uuid()
date_created    | timestamp without time zone | not null default now()
sequence_id     | bigint                      | not null default nextval('documents__sequence_id__seq'::regclass)
version         | integer                     | not null default 0
source          | text                        | not null
source_id       | text                        | not null
ingestion_date  | timestamp without time zone | not null

Indexes:
    "documents__pkey" PRIMARY KEY, btree (uid)
    "documents__sequence_id__unique" UNIQUE CONSTRAINT, btree (sequence_id)
    "documents__source__source_id__deleted" UNIQUE, btree (source, source_id)
    "documents__ingestion_date__idx" btree (ingestion_date)
    "documents__source_id__source__idx" btree (source_id, source)

我怀疑问题是这样的:“第一个事务按顺序锁定了具有source_id alpha，beta，gamma的行，而第二个事务按相反的顺序锁定了具有source_id delta，gamma的行，并且死锁发生在它们都锁定了“ Gamma 和增量”，但是这里的时机非常紧张!

对此的解决方案是什么？按source_id对值列表进行排序？

最佳答案

我可以想到三种解决方案:

每个语句仅插入一行，但是效率低下。

在对行进行排序之前，请先对它们进行排序。

如果遇到死锁或序列化错误，请重试事务。

我更喜欢第三个解决方案，除非错误经常发生。

关于postgresql - Postgres在并发更新中陷入僵局，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/46366324/