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创建临时表不会导致pg_class表碎片

[英]Does creating a temp table cause the pg_class table to fragment

原文 2016-08-11 15:16:34 2 1 performance/ postgresql

MS-SQL developer on this end working in a Postgres shop (PG 8.4 and PG 9.4) 为此，MS-SQL开发人员在Postgres商店中工作（PG 8.4和PG 9.4）

Another developer mentioned as a reason for not using temp tables in Postgres SQL is that it will cause fragmentation in the Postgres system tables (pg_class specifically) leading to performance degradation. 提到的另一个在Postgres SQL中不使用临时表的原因是，这将导致Postgres系统表（特别是pg_class）中的碎片，从而导致性能下降。 Is this true? 这是真的？

Cheers 干杯

1 个解决方案

Fragmentation is a rather meaningless term when applied to a database table, as they always consist of blocks of a fixed size (8 KB in PostgreSQL). 当将碎片应用于数据库表时，它是一个毫无意义的术语，因为它们始终由固定大小的块（PostgreSQL中为8 KB）组成。

What is true is that using a temporary table will create entries in system catalog tables and indexes like pg_class which will be deleted when the temporary table goes away. 确实，使用临时表将在系统目录表和pg_class索引中创建条目，当临时表消失时，这些条目将被删除。 If you do a lot of that, the same thing could happen as with any other table that is heavily updated: autovacuum may not be able to keep up, and your system catalog tables and their indexes might get bloated. 如果执行大量操作 ，则可能会发生与其他任何表进行大量更新的情况相同的情况：自动清理可能无法跟上，并且系统目录表及其索引可能会膨胀。

There is a proposal on pgsql-hackers right now to invent a new kind of temporary table that avoids this kind of problem. 现在有一个关于pgsql-hackers的建议，发明一种避免这种问题的新型临时表。

However, unless you use really a lot of temporary tables all the time, there is no need to worry. 但是，除非您一直真正使用大量临时表，否则不必担心。 Just use them when you need to! 只需在需要时使用它们即可！