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Add support for asynchronous fetching, the `async_capable` table option

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
48/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Quiet
Tech stack
c, clickhouse, postgresql
Domain
databases

Research direction

Start with PostgreSQL's postgres_fdw changes referenced in commits 27e1f1456, bb684c82, and 5c854e7, then read the FDW Routines for Asynchronous Execution documentation. Trace pg_clickhouse's foreign-table option handling and fetch entry points; done means async_capable is supported and fetches can execute asynchronously alongside other foreign tables.

Written by the indexing model from the issue text.

Description

enhancement planner

Add support for the async_capable option to allow async fetching of result sets, as described in All Your GUCs in a Row: enable_async_append and the FDW Routines for Asynchronous Execution docs. The option was added to postgres_fdw in postgres/postgres@27e1f1456 and modified in postgres/postgres@bb684c82 and postgres/postgres@5c854e7.

This will allow Postgres to execute fetches via pg_clickhouse asynchronously with other foreign tables, via pg_clickhouse or otherwise. Note, however, that its utility will be limited for fetches from the same foreign server, as pg_clickhouse uses a a single connection for all queries for a given server, so they'll run synchronously. Thus this feature, while desirable, is less important than improving join pushdown in general.

Suggested by @heavycrystal.

Dominant language
C
Stars
284
Forks
21
Avg merge
23h 1m
Merged PRs (30d)
20

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