Multithreading in C functions for Postgres

Question

I'm reading documentation for SPI https://www.postgresql.org/docs/13/spi.html And I have a few questions:

is there any way to use multithreading in C to connect to Postgres (via SPI or Libpq) and read data from one table? (for example, one thread reads data from 1 to 100 rows, second from 101 to 200 etc).
I know that Postgres can use workers (for SELECT, for example), but how SPI will react to that (if I send command "select * from table_name")

The SQL language and PostGreSQL support pagination using LIMIT and OFFSET... so it should be easy to route different subsets of a query to different threads. I'm not sure how (if) it will improve performance, that would depend on specific use cases. — Myst
– Myst, Commented Mar 24, 2021 at 6:39
Do you expect faster execution or there is other reason for MT? — i486
– i486, Commented Mar 24, 2021 at 8:43
Yes, I want to work with big tables (like 1mil rows) and I want to have faster execution. — Avartiai
– Avartiai, Commented Mar 26, 2021 at 11:02

Laurenz Albe · Accepted Answer · 2021-03-24 07:18:12Z

1

Do not use multithreading in PostgreSQL backends. The system is not laid out for that, and interesting, yet undesirable, things are bound to happen if you do.

Using a custom background worker is the better idea. There is no problem with using SPI to process statements once you have attached to a database.

answered Mar 24, 2021 at 7:18

Laurenz Albe

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