fix: enforce 255-character identifier length limit for Databricks relations

Add relation_max_name_length() returning 255 and a __post_init__
validation to DatabricksRelation, following the same pattern used by
the Postgres adapter. This catches overly-long table names (commonly
generated by store_failures for tests with verbose names) at relation
creation time with a clear error message instead of a cryptic runtime
DatabricksExecutionError from the SQL engine.

Closes #1309

Author: psaikaushik

dbt/adapters/databricks/relation.py

@@ -18,6 +18,13 @@
 
 KEY_TABLE_PROVIDER = "Provider"
 
+# Databricks (Unity Catalog / Hive Metastore) enforces a 255-character limit
+# on table and view names. This constant is used by relation_max_name_length()
+# to validate identifier lengths at relation creation time rather than at
+# SQL execution time, providing a clear error message instead of a cryptic
+# DatabricksExecutionError.
+MAX_CHARACTERS_IN_IDENTIFIER = 255
+
 
 @dataclass
 class DatabricksQuotePolicy(Policy):
@@ -86,6 +93,27 @@ class DatabricksRelation(BaseRelation):
     databricks_table_type: Optional[DatabricksTableType] = None
     temporary: Optional[bool] = False
 
+    def __post_init__(self):
+        # Validate identifier length against Databricks' 255-character limit.
+        # Check self.type to exclude test relation identifiers that may not
+        # have a type set yet.
+        if (
+            self.identifier is not None
+            and self.type is not None
+            and len(self.identifier) > self.relation_max_name_length()
+        ):
+            raise DbtRuntimeError(
+                f"Relation name '{self.identifier}' "
+                f"is longer than {self.relation_max_name_length()} characters. "
+                f"Databricks has a maximum identifier length of "
+                f"{self.relation_max_name_length()} characters. "
+                f"If this is a store_failures table, consider using a shorter "
+                f"test name or setting a custom alias."
+            )
+
+    def relation_max_name_length(self):
+        return MAX_CHARACTERS_IN_IDENTIFIER
+
     @classmethod
     def __pre_deserialize__(cls, data: dict[Any, Any]) -> dict[Any, Any]:
         data = super().__pre_deserialize__(data)