Support composite types with fields that are of type `citext`

• asyncpg version: 0.28
• PostgreSQL version: 15
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: Local version
• Python version: 3.11
• Platform: Linux
• Do you use pgbouncer?: No
• Did you install asyncpg with pip?: Yes
• If you built asyncpg locally, which version of Cython did you use?: -
• Can the issue be reproduced under both asyncio and
  uvloop?: not tested

I am using citext for fields that really need to be citext (as in, I care about the case only for displaying but other than that the case should not matter). Now I have a query that goes like

SELECT * FROM project WHERE (owner::citext, name::citext)::record = ANY($1);

Throughout asyncpg it is mentioned to get this to work (normally) you add a composite type. So we add a composite type and cast the array to the composite type.

CREATE TYPE project_fqn AS (
    owner citext,
    name citext
);

SELECT * FROM project WHERE (owner::citext, name::citext) = ANY($1::project_fqn[]);

Sadly this fails due to an <class 'asyncpg.exceptions._base.UnsupportedClientFeatureError'>: cannot decode type "public"."project_fqn": text encoding of composite types is not supported. error. It can be "fixed" by changing all citext types for a text type but then we lose the case insensitive search.

Is this something that can be fixed or are there any workarounds? I tried doing a set_builtin_type_codec("citext", codec_name=25) but that seems to have no impact.

Some references:

• https://github.com/MagicStack/asyncpg/issues/476
• https://github.com/MagicStack/asyncpg/issues/82

Tái hiện SQL đã được báo cáo bằng asyncpg 0.28 với PostgreSQL 15 và một kiểu composite có các trường là citext. Bắt đầu bằng cách lần theo quá trình giải mã composite và điểm vào set_builtin_type_codec("citext"); hoàn thành nghĩa là các giá trị project_fqn[] được giải mã mà không có UnsupportedClientFeatureError, đồng thời vẫn giữ nguyên hành vi của citext.