Registry, tw interface draft, sub handler

plugin/lib.py

@@ -0,0 +1,21 @@
+from typing import Any
+from psycopg import sql
+
+from data import RawExpr, Expression
+
+
+def LOWER(expression: Expression) -> RawExpr:
+    """
+    Wrap an Expression in the SQL function LOWER().
+    """
+    expr, values = expression.as_tuple()
+    final_expr = sql.SQL("LOWER({})").format(expr)
+    final_values = values
+
+    return RawExpr(final_expr, final_values)
+
+def asexpr(value: Any) -> RawExpr:
+    """
+    Turn a value into an expression.
+    """
+    return RawExpr(sql.Placeholder(), (value,))