out of range temporal cols as UnknownColType

issue 786 #786

data_diff/databases/redshift.py

@@ -1,4 +1,5 @@
-from typing import ClassVar, List, Dict, Type
+import logging
+from typing import ClassVar, List, Dict, Optional, Type
 
 import attrs
 
@@ -10,6 +11,7 @@
     FractionalType,
     DbPath,
     TimestampTZ,
+    UnknownColType,
 )
 from data_diff.databases.postgresql import (
     BaseDialect,
@@ -21,6 +23,8 @@
     PostgresqlDialect,
 )
 
+logger = logging.getLogger("redshift")
+
 
 @attrs.define(frozen=False)
 class Dialect(PostgresqlDialect):
@@ -183,3 +187,29 @@ def _normalize_table_path(self, path: DbPath) -> DbPath:
         raise ValueError(
             f"{self.name}: Bad table path for {self}: '{'.'.join(path)}'. Expected format: table, schema.table, or database.schema.table"
         )
+
+    def _refine_coltypes(
+        self, table_path: DbPath, col_dict: Dict[str, ColType], where: str | None = None, sample_size=64
+    ):
+        super()._refine_coltypes(table_path, col_dict, where, sample_size)
+        refine_columns = {k for k, v in col_dict.items() if isinstance(v, (TemporalType))}
+        if not refine_columns:
+            return
+
+        # values in a timestamp column in redshift can technically be "out of range"
+        # this causes issues when treating them as a valid timestamp, so do not treat a column with
+        # out of range issues as a TemporalType
+        for column_name in refine_columns:
+            # TRUE = strict_mode
+            try:
+                # check if the min + max are out of range
+                self.query(
+                    f"select to_timestamp(max({column_name}),'YYYY-mm-dd HH24:MI:SS.US', TRUE), "
+                    + f"to_timestamp(min({column_name}),'YYYY-mm-dd HH24:MI:SS.US', TRUE) from {'.'.join(table_path)}"
+                )
+            except Exception:
+                self.query("rollback")
+                logger.warning(f"Temporal column {column_name} has out of range values, falling back to text.")
+                col_dict[column_name] = UnknownColType("Temporal type contains out of range values.")
+
+        return