Execute single-statement migrations without batch_execute about diesel HOT 6 CLOSED

Thanks for filling this PR. Can you clarify if that's a CockroachDB specific feature or if that's something that could happen with other backends as well? In the first case it's just a matter of using a not officially supported database which does not support all required features, which is something that should be fixed in that database system or by providing a third party backend/connection implementation.

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@weiznich SET CLUSTER SETTING is CockroachDB specific feature, but the case of executing a single statement as batch in diesel migrations is misleading imho.

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Well, as a migration can and will contain several statements in general it's the only meaningful solution to use batch_execute for this, as otherwise we would need to have a full sql parsers to detect if a migration is a single or multiple statements. That's clearly out of scope for this project, especially if that is related to an feature of a not supported backend.

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@weiznich The problem is also related to supported backends I think:

For example if I turn off multi-statement execution in MySQL (MYSQL_OPTION_MULTI_STATEMENTS_OFF) and try to run migrations contains single statements only I will get an error.

as otherwise we would need to have a full sql parsers to detect if a migration is a single or multiple statements.

Multiple statements separates with ; in most cases, isn't it enough to detect multi-statement queries?

p.s. Or maybe just run a query as single-statement, and if error occurs - run as batch?

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Multiple statements separates with ; in most cases, isn't it enough to detect multi-statement queries?

That will not work for queries like UPDATE some_table SET foo = ';'

For example if I turn off multi-statement execution in MySQL (MYSQL_OPTION_MULTI_STATEMENTS_OFF) and try to run migrations contains single statements only I will get an error.

Given that this is not the default I do not see that as critical problem. We likely would accept a PR that improves the handling of such situations by just enforcing that this option is not set.

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@weiznich Ok, got your point. 👌

Closing the issue, due the problem is out of project scope.

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