From 3dc9a4a2392d033f9d1bd79dd6b6ecea6281a61c Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Mon, 16 Dec 2019 17:06:43 -0500
Subject: introduce deferred lambdas

The coercions system allows us to add in lambdas as arguments
to Core and ORM elements without changing them at all.   By allowing
the lambda to produce a deterministic cache key where we can also
cheat and yank out literal parameters means we can move towards
having 90% of "baked" functionality in a clearer way right in
Core / ORM.

As a second step, we can have whole statements inside the lambda,
and can then add generation with __add__(), so then we have
100% of "baked" functionality with full support of ad-hoc
literal values.

Adds some more short_selects tests for the moment for comparison.

Other tweaks inside cache key generation as we're trying to
approach a certain level of performance such that we can
remove the use of "baked" from the loader strategies.

As we have not yet closed #4639, however the caching feature
has been fully integrated as of
b0cfa7379cf8513a821a3dbe3028c4965d9f85bd, we will also
add complete caching documentation here and close that issue
as well.

Closes: #4639
Fixes: #5380
Change-Id: If91f61527236fd4d7ae3cad1f24c38be921c90ba
---
 lib/sqlalchemy/sql/expression.py | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'lib/sqlalchemy/sql/expression.py')

diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py
index e25063372..37441a125 100644
--- a/lib/sqlalchemy/sql/expression.py
+++ b/lib/sqlalchemy/sql/expression.py
@@ -29,6 +29,8 @@ __all__ = [
     "Insert",
     "Join",
     "Lateral",
+    "LambdaElement",
+    "StatementLambdaElement",
     "Select",
     "Selectable",
     "TableClause",
@@ -59,6 +61,7 @@ __all__ = [
     "join",
     "label",
     "lateral",
+    "lambda_stmt",
     "literal",
     "literal_column",
     "not_",
@@ -135,6 +138,9 @@ from .functions import func  # noqa
 from .functions import Function  # noqa
 from .functions import FunctionElement  # noqa
 from .functions import modifier  # noqa
+from .lambdas import lambda_stmt  # noqa
+from .lambdas import LambdaElement  # noqa
+from .lambdas import StatementLambdaElement  # noqa
 from .selectable import Alias  # noqa
 from .selectable import AliasedReturnsRows  # noqa
 from .selectable import CompoundSelect  # noqa
-- 
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