Thank you so much, Mike!
I roughly had that same @compiles in my tests, but I didn't trust myself...
and the .dbapi looked like what I wanted, but I really wasn't sure!
On Monday, March 8, 2021 at 4:36:03 PM UTC-5 Mike Bayer wrote:
>
>
> On Mon, Mar 8, 2021, at 12:06 PM, 'Jonathan Vanasco' via sqlalchemy wrote:
>
> I have a project that, in a few rare situations, may run on a version of
> sqlite that does not support function indexes, and "need" to run a unique
> index on `lower(name)`. For simplicity, I'll just use a normal index on
> correct systems,
>
> I'm trying to figure out the best way to implement this.
>
> 1. in terms of sqlite3, what is the best way to access the version
> Sqlalchemy is using? the import is in a classmethod, and could either be
> pysqlite2 or sqlite3? i seriously doubt anyone would deploy with
> pysqlite2, but I feel like I should do things the right way.
>
>
> you'd get this from the dbapi:
>
> >>> from sqlalchemy import create_engine
> >>> e = create_engine("sqlite://")
> >>> e.dialect.dbapi.sqlite_version
> '3.34.1'
>
>
>
>
>
> 2. What is the best way to implement this contextual switch? I thought
> about a `expression.FunctionElement` with custom `@compiles`.
>
>
> yeah that is probably the best approach
>
> from sqlalchemy.sql import expression
> from sqlalchemy.ext.compiler import compiles
>
> class maybe_lower(expression.FunctionElement):
> type = String()
>
> @compiles(maybe_lower, 'sqlite')
> def sl_maybe_lower(element, compiler, **kw):
> args = list(element.clauses)
> if compiler.dialect.dbapi_version < ...:
> return "LOWER(%s)" % (compiler.process(args[0], **kw))
> else:
> return compiler.process(args[0], **kw)
>
> @compiles(maybe_lower)
> def default_maybe_lower(element, compiler, **kw):
> args = list(element.clauses)
> return compiler.process(args[0], **kw)
>
>
>
>
>
> --
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> The Python SQL Toolkit and Object Relational Mapper
>
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