Make version table customizable by dialects

[maver1ck]

Describe the use case
Starrocks is Open-Source, High-Performance Analytical Database.
https://www.starrocks.io

Databases / Backends / Drivers targeted

Starrocks

Example Use
Management of Tables in Starrocks.

Additional context
I will create PR with detailed technical solution.

Have a nice day!

[zzzeek]

Alembic only includes support for SQLAlchemy's built-in dialects: oracle, postgresql, sqlite, mysql, mssql. To add alembic implementations to third party dialects, you should contribute your PR to that dialect's github repository.

[maver1ck]

@zzzeek I understand.
But this query makes this support very difficult to achieve in starrocks dialect because sqlalchemy assumes that version_num is first column in alembic_version table. This change doesn't have any impact on existing behaviour.

[zzzeek]

the alembic_version table has only one column. it is by definition the first column in the table.

[zzzeek]

both statements are identical

>>> from sqlalchemy import table, column
>>> alembic_version = table("alembic_version", column("version_num"))
>>> print(alembic_version.select())
SELECT alembic_version.version_num 
FROM alembic_version
>>> print(alembic_version.select().with_only_columns(alembic_version.c.version_num))
SELECT alembic_version.version_num 
FROM alembic_version

[zzzeek]

this is why, let's open a discussion and step through what's happening

[CaselIT]

I think the issue is that they want to use a table that has two columns with an autoincrement id as the first column. Not sure if it's a constraint of starrocks the fact that it requires one such column as the fist one.

[sqla-tester]

Maciek Bryński has proposed a fix for this issue in the main branch:

Add ability to configure alembic_version table in DialectImpl https://gerrit.sqlalchemy.org/c/sqlalchemy/alembic/+/5556

[zzzeek]

ok you're released thanks for the patience

[maver1ck]

Thanks @zzzeek.