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)
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
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SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
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