Fixed #24920 -- Added support for DecimalField with no precision.

Thanks Lily for the review.

3 files changed, 12 insertions, 3 deletions

diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
index e2728afea5..42b37ab3c2 100644
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -89,6 +89,12 @@ def _get_varchar_column(data):
     return "varchar(%(max_length)s)" % data
 
 
+def _get_decimal_column(data):
+    if data["max_digits"] is None and data["decimal_places"] is None:
+        return "numeric"
+    return "numeric(%(max_digits)s, %(decimal_places)s)" % data
+
+
 class DatabaseWrapper(BaseDatabaseWrapper):
     vendor = "postgresql"
     display_name = "PostgreSQL"
@@ -105,7 +111,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         "CharField": _get_varchar_column,
         "DateField": "date",
         "DateTimeField": "timestamp with time zone",
-        "DecimalField": "numeric(%(max_digits)s, %(decimal_places)s)",
+        "DecimalField": _get_decimal_column,
         "DurationField": "interval",
         "FileField": "varchar(%(max_length)s)",
         "FilePathField": "varchar(%(max_length)s)",
diff --git a/django/db/backends/postgresql/features.py b/django/db/backends/postgresql/features.py
index 5bbf4b86cb..5e4ed320be 100644
--- a/django/db/backends/postgresql/features.py
+++ b/django/db/backends/postgresql/features.py
@@ -68,6 +68,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     supports_covering_indexes = True
     supports_stored_generated_columns = True
     supports_nulls_distinct_unique_constraints = True
+    supports_no_precision_decimalfield = True
     can_rename_index = True
     test_collations = {
         "deterministic": "C",
diff --git a/django/db/backends/postgresql/introspection.py b/django/db/backends/postgresql/introspection.py
index 791d729ea4..69dd776aa3 100644
--- a/django/db/backends/postgresql/introspection.py
+++ b/django/db/backends/postgresql/introspection.py
@@ -137,8 +137,10 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
                 # display_size is always None on psycopg2.
                 line.internal_size if line.display_size is None else line.display_size,
                 line.internal_size,
-                line.precision,
-                line.scale,
+                # precision and scale are always 2^16 - 1 on psycopg2 for
+                # DecimalFields with no precision.
+                None if line.precision == 2**16 - 1 else line.precision,
+                None if line.scale == 2**16 - 1 else line.scale,
                 *field_map[line.name],
             )
             for line in cursor.description