review: bigint-unsigned warning names the real hazard (describe round-trip) and the lossless escape hatch (decimal(20,0)); fix the match-vs-fullmatch comment

Author: dimitri-yatsenko

src/datajoint/heading.py

@@ -484,10 +484,10 @@ def _init_from_database(self) -> None:
                 in_key=(attr["key"] == "PRI"),
                 nullable=attr["nullable"],  # Already boolean from parse_column_info
                 autoincrement=bool(re.search(r"auto_increment", attr["extra"], flags=re.I)),
-                # NOTE: these use prefix matching, unlike match_type() which requires a
-                # full match. attr["type"] is reported by the server and is not
-                # normalized, so PostgreSQL spellings such as "double precision" and
-                # "timestamp without time zone" are matched on their leading word.
+                # NOTE: .match() here is equivalent to .fullmatch() — every pattern in
+                # these tuples is anchored with $ — so this is not prefix matching.
+                # Server-reported spellings match because the patterns themselves cover
+                # them, not because of the matching mode.
                 numeric=any(TYPE_PATTERN[t].match(attr["type"]) for t in ("DECIMAL", "NUMERIC", "INTEGER", "FLOAT")),
                 string=any(TYPE_PATTERN[t].match(attr["type"]) for t in ("ENUM", "TEMPORAL", "STRING")),
                 is_blob=any(TYPE_PATTERN[t].match(attr["type"]) for t in ("BYTES", "NATIVE_BLOB")),

src/datajoint/migrate.py

@@ -202,8 +202,13 @@ def analyze_columns(schema: Schema) -> dict:
                         logger.warning(
                             f"Column `{col_info['table']}`.`{col_info['column']}` is "
                             "`bigint unsigned` and will be labeled `int64`. DataJoint 2.0 "
-                            "provides no unsigned integer types; values above 2**63-1 do "
-                            "not fit in int64. Verify the stored range before migrating."
+                            "provides no unsigned integer types. The physical column and "
+                            "stored data are unchanged by migration, but `describe()` will "
+                            "report `int64`, so a describe->recreate->copy round trip "
+                            "produces a signed column: values above 2**63-1 do not survive "
+                            "that copy. Verify the stored range before migrating; if the "
+                            "full unsigned range is in use, declare the attribute as "
+                            "decimal(20,0), which holds it losslessly."
                         )
                     result["needs_migration"].append(col_info)
                 # Types that don't need migration (varchar, date, datetime, json, etc.)