Fix: handle column default types correctly in SchemaCache

CHANGELOG.md

@@ -4,7 +4,8 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
-
+### Fixed
+- **fix**: Improved handling of column default values in `SchemaCache`. This addresses issue #3706 by ensuring all relevant cases are covered, including scenarios where `ad.adbin` is not NULL.
 
 ### Added
 
@@ -1095,3 +1096,6 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 - Make filter position match docs, e.g. `?order=col.asc` rather
   than `?order=asc.col`.
+
+
+

src/PostgREST/SchemaCache.hs

@@ -622,10 +622,12 @@ tablesSqlQuery =
           d.description AS description,
           -- typbasetype and typdefaultbin handles `CREATE DOMAIN .. DEFAULT val`,  attidentity/attgenerated handles generated columns, pg_get_expr gets the default of a column
           CASE
-            WHEN t.typbasetype  != 0  THEN pg_get_expr(t.typdefaultbin, 0)
-            WHEN a.attidentity  = 'd' THEN format('nextval(%L)', seq.objid::regclass)
-            WHEN a.attgenerated = 's' THEN null
-            ELSE pg_get_expr(ad.adbin, ad.adrelid)::text
+            WHEN a.attdefault IS NOT NULL THEN pg_get_expr(a.attdefault, a.attrelid)::text  -- Column default
+            WHEN t.typbasetype != 0 THEN pg_get_expr(t.typdefaultbin, 0)  -- Domain default
+            WHEN a.attidentity = 'd' THEN format('nextval(%L)', seq.objid::regclass)  -- Identity column
+            WHEN a.attgenerated = 's' THEN NULL  -- Generated column
+            WHEN ad.adbin IS NOT NULL THEN pg_get_expr(ad.adbin, ad.adrelid)::text  -- Other default expressions
+            ELSE NULL
           END AS column_default,
           not (a.attnotnull OR t.typtype = 'd' AND t.typnotnull) AS is_nullable,
           CASE

test/spec/Feature/Query/InsertSpec.hs

@@ -563,6 +563,16 @@ spec actualPgVersion = do
                 }|])
               { matchStatus  = 400 }
 
+        it "inserts a default on a DOMAIN with default" $ 
+          request methodPost "/evil_friends?columns=id,name" 
+          [("Prefer", "return=representation"), ("Prefer", "missing=default")] 
+          [json| { "name": "Lu" } |] 
+          `shouldRespondWith` 
+          [json| [{"id": 666, "name": "Lu"}] |] 
+          { matchStatus  = 201 
+          , matchHeaders = ["Preference-Applied" <:> "missing=default, return=representation"] 
+          }
+
         it "inserts a default on a DOMAIN with default" $
           request methodPost "/evil_friends?columns=id,name" [("Prefer", "return=representation"), ("Prefer", "missing=default")]
               [json| { "name": "Lu" } |]