Change postgres name truncation logic to be overridable. (#5656)

* Change postgres name truncation logic to be overridable. Add exception with debugging instructions.

* Add changelog.

Co-authored-by: Mila Page <versusfacit@users.noreply.github.com>
(cherry picked from commit 0d02446)

.changes/unreleased/Fixes-20220815-230409.yaml

@@ -0,0 +1,7 @@
+kind: Fixes
+body: Finishing logic upgrade to Redshift for name truncation collisions.
+time: 2022-08-15T23:04:09.173645-07:00
+custom:
+  Author: versusfacit
+  Issue: "5586"
+  PR: "5656"

core/dbt/adapters/cache.py

@@ -1,3 +1,4 @@
+import re
 import threading
 from copy import deepcopy
 from typing import Any, Dict, Iterable, List, Optional, Set, Tuple
@@ -413,9 +414,24 @@ def _check_rename_constraints(self, old_key, new_key):
         :raises InternalError: If the new key is already present.
         """
         if new_key in self.relations:
+            # Tell user when collision caused by model names truncated during
+            # materialization.
+            match = re.search("__dbt_backup|__dbt_tmp$", new_key.identifier)
+            if match:
+                truncated_model_name_prefix = new_key.identifier[: match.start()]
+                message_addendum = (
+                    "\n\nName collisions can occur when the length of two "
+                    "models' names approach your database's builtin limit. "
+                    "Try restructuring your project such that no two models "
+                    "share the prefix '{}'.".format(truncated_model_name_prefix)
+                    + " Then, clean your warehouse of any removed models."
+                )
+            else:
+                message_addendum = ""
+
             dbt.exceptions.raise_cache_inconsistent(
-                "in rename, new key {} already in cache: {}".format(
-                    new_key, list(self.relations.keys())
+                "in rename, new key {} already in cache: {}{}".format(
+                    new_key, list(self.relations.keys()), message_addendum
                 )
             )
 

plugins/postgres/dbt/include/postgres/macros/adapters.sql

@@ -146,7 +146,7 @@
       {% set suffix = suffix ~ dtstring %}
     {% endif %}
     {% set suffix_length = suffix|length %}
-    {% set relation_max_name_length = 63 %}
+    {% set relation_max_name_length = base_relation.relation_max_name_length() %}
     {% if suffix_length > relation_max_name_length %}
         {% do exceptions.raise_compiler_error('Relation suffix is too long (' ~ suffix_length ~ ' characters). Maximum length is ' ~ relation_max_name_length ~ ' characters.') %}
     {% endif %}