"<i>What will happen if you insert 5 billion rows as independent transactions?<\/i>如果将 50 亿行作为独立事务插入会发生什么？<\/b> <i>What will the vaccum do to the xmin column?<\/i> vaccum 会对 xmin 列做什么？<\/b>"
[英]What will happen if you insert 5 billion rows as independent transactions? What will the vaccum do to the xmin column?
问题描述
I understand that xmin is limited to 2^32-1, about 4 billion entries.
我了解 xmin 限制为 2^32-1，大约 40 亿个条目。 Vacuum cleans up dead tuples, postgres maintains a transaction for every update to a row and those are cleaned up as a process of vacuum. Vacuum 清理死元组，postgres 为对行的每次更新维护一个事务，并且这些事务作为一个清理过程被清理。 Lets say, i am just inserting 5 billion records all independent transactions.可以说，我只是插入了 50 亿条记录，所有独立交易。
- What is the dead tuple, in the above scenario?在上述场景中，死元组是什么？<\/li>
- When does the vacuum run automatically, around the 2 billion entries, what does it clean at this point?真空何时自动运行，大约 20 亿个条目，此时它会清理什么？<\/li>
- what happens to the xmin for the 1st 2 billion records as the vacuum process starts ?当真空过程开始时，第一个 20 亿条记录的 xmin 会发生什么变化？<\/li>
- Let's say, i stored the xmin of the 100,000 transactions, as in keep pushing the insert transactions.比方说，我存储了 100,000 个事务的 xmin，因为不断推送插入事务。 After i inserted the 5 billion transactions, i want to query for all of my transaction after the 100,000 xmin and xmin < 500,000.插入 50 亿笔交易后，我想查询 100,000 xmin 和 xmin < 500,000 之后的所有交易。 Will this work?这行得通吗？<\/li><\/ol>"
2 个解决方案
解决方案1
0 2022-02-05 20:58:30
Postgresql will trigger an autovacuum to avoid WRAPAROUND, the autovacuum will freez old transaction. Postgresql 将触发自动清理以避免 WRAPROUND，自动清理将冻结旧事务。
you can read: https:\/\/www.cybertec-postgresql.com\/en\/autovacuum-wraparound-protection-in-postgresql\/<\/a>您可以阅读： https<\/a> :\/\/www.cybertec-postgresql.com\/en\/autovacuum-wraparound-protection-in-postgresql\/
"
解决方案2
0 2022-02-06 02:22:05
In old versions, freezing a tuple involved changing the xmin to a magic value of 2. see src\/include\/access\/transam.h:在旧版本中，冻结元组涉及将 xmin 更改为魔法值 2。请参阅 src\/include\/access\/transam.h：
#define FrozenTransactionId ((TransactionId) 2)
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