Fix: Always set the varchar size when creating a table in redshift (#1881)

* Fix: Always set the varchar size when creating a table in redshift

* Cast NULL instead of the original projection

Author: izeigerman

sqlmesh/core/engine_adapter/redshift.py

@@ -108,13 +108,20 @@ def _create_table_exp(
                     if target["name"] == "TARGETENTRY":
                         resdom = target["resdom"]
                         # https://github.com/postgres/postgres/blob/master/src/include/catalog/pg_type.dat
-                        if resdom["restype"] == "1043" and resdom["restypmod"] == "- 1":
+                        if resdom["restype"] == "1043":
+                            size = (
+                                int(resdom["restypmod"]) - 4
+                                if resdom["restypmod"] != "- 1"
+                                else "MAX"
+                            )
+                            # Cast NULL instead of the original projection to trick the planner into assigning a
+                            # correct type to the column.
                             select.select(
                                 exp.cast(
-                                    exp.to_identifier(resdom["resname"]),
-                                    "VARCHAR(MAX)",
+                                    exp.null(),
+                                    f"VARCHAR({size})",
                                     dialect=self.dialect,
-                                ),
+                                ).as_(resdom["resname"]),
                                 copy=False,
                             )
                         else:

tests/core/engine_adapter/test_redshift.py

@@ -84,8 +84,8 @@ def test_create_table_from_query_exists_no_if_not_exists(
 
     assert to_sql_calls(adapter) == [
         'EXPLAIN VERBOSE CREATE TABLE "test_table" AS SELECT "a", "b", "x" + 1 AS "c", "d" AS "d" FROM "table"',
-        'CREATE TABLE "test_table" AS SELECT CAST("a" AS VARCHAR(MAX)), "b", CAST("c" '
-        'AS VARCHAR(MAX)), CAST("d" AS VARCHAR(MAX)) FROM (SELECT "a", "b", "x" + 1 '
+        'CREATE TABLE "test_table" AS SELECT CAST(NULL AS VARCHAR(MAX)) AS "a", CAST(NULL AS VARCHAR(60)) AS "b", CAST(NULL '
+        'AS VARCHAR(MAX)) AS "c", CAST(NULL AS VARCHAR(MAX)) AS "d" FROM (SELECT "a", "b", "x" + 1 '
         'AS "c", "d" AS "d" FROM "table") AS "_subquery"',
     ]