postgres: Column merging for table inheritence

internal/endtoend/testdata/ddl_create_table_inherits/postgresql/pgx/v4/schema.sql

@@ -11,3 +11,8 @@ CREATE TABLE person (
 CREATE TABLE organisation (
     legal_name text
 ) INHERITS (party);
+
+CREATE TABLE llc (
+   incorporation_date timestamp,
+   legal_name text NOT NULL
+) INHERITS (organisation); 

internal/endtoend/testdata/ddl_create_table_inherits/postgresql/pgx/v5/schema.sql

@@ -11,3 +11,8 @@ CREATE TABLE person (
 CREATE TABLE organisation (
     legal_name text
 ) INHERITS (party);
+
+CREATE TABLE llc (
+   incorporation_date timestamp,
+   legal_name text NOT NULL
+) INHERITS (organisation); 

internal/endtoend/testdata/ddl_create_table_inherits/postgresql/stdlib/schema.sql

@@ -11,3 +11,8 @@ CREATE TABLE person (
 CREATE TABLE organisation (
     legal_name text
 ) INHERITS (party);
+
+CREATE TABLE llc (
+   incorporation_date timestamp,
+   legal_name text NOT NULL
+) INHERITS (organisation); 

internal/endtoend/testdata/ddl_create_table_invalid_inherits/postgresql/stdlib/query.sql

@@ -0,0 +1,5 @@
+-- name: GetAllParties :many
+SELECT * FROM party;
+
+-- name: GetAllOrganisations :many
+SELECT * FROM organisation;

internal/endtoend/testdata/ddl_create_table_invalid_inherits/postgresql/stdlib/schema.sql

@@ -0,0 +1,7 @@
+CREATE TABLE party (
+    name text NOT NULL
+);
+
+CREATE TABLE organisation (
+    name integer NOT NULL
+) INHERITS (party);

internal/endtoend/testdata/ddl_create_table_invalid_inherits/postgresql/stdlib/sqlc.json

@@ -0,0 +1,12 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "postgresql",
+      "name": "querytest",
+      "schema": "schema.sql",
+      "queries": "query.sql"
+    }
+  ]
+}

internal/endtoend/testdata/ddl_create_table_invalid_inherits/postgresql/stdlib/stderr.txt

@@ -0,0 +1,2 @@
+# package querytest
+schema.sql:1:1: column "name" has a type conflict

internal/sql/catalog/table.go

@@ -240,20 +240,28 @@ func (c *Catalog) createTable(stmt *ast.CreateTableStmt) error {
 	}
 
 	tbl := Table{Rel: stmt.Name, Comment: stmt.Comment}
-	m := make(map[string]struct{}) // used to check for duplicate column names
+	coltype := make(map[string]ast.TypeName) // used to check for duplicate column names
+	seen := make(map[string]bool)            // used to check for duplicate column names
 	for _, inheritTable := range stmt.Inherits {
 		t, _, err := schema.getTable(inheritTable)
 		if err != nil {
 			return err
 		}
 		// check and ignore duplicate columns
 		for _, col := range t.Columns {
-			if _, ok := m[col.Name]; ok {
+			if notNull, ok := seen[col.Name]; ok {
+				seen[col.Name] = notNull || col.IsNotNull
+				if a, ok := coltype[col.Name]; ok {
+					if !sameType(&a, &col.Type) {
+						return fmt.Errorf("column \"%s\" has a type conflict", col.Name)
+					}
+				}
 				continue
-			} else {
-				m[col.Name] = struct{}{}
-				tbl.Columns = append(tbl.Columns, col)
 			}
+
+			seen[col.Name] = col.IsNotNull
+			coltype[col.Name] = col.Type
+			tbl.Columns = append(tbl.Columns, col)
 		}
 	}
 
@@ -272,6 +280,16 @@ func (c *Catalog) createTable(stmt *ast.CreateTableStmt) error {
 		}
 	} else {
 		for _, col := range stmt.Cols {
+			if notNull, ok := seen[col.Colname]; ok {
+				seen[col.Colname] = notNull || col.IsNotNull
+				if a, ok := coltype[col.Colname]; ok {
+					if !sameType(&a, col.TypeName) {
+						return fmt.Errorf("column \"%s\" has a type conflict", col.Colname)
+					}
+				}
+				continue
+			}
+
 			tc := &Column{
 				Name:      col.Colname,
 				Type:      *col.TypeName,
@@ -293,6 +311,14 @@ func (c *Catalog) createTable(stmt *ast.CreateTableStmt) error {
 			tbl.Columns = append(tbl.Columns, tc)
 		}
 	}
+
+	// If one of the merged columns was not null, mark the column as not null
+	for i := range tbl.Columns {
+		if notNull, ok := seen[tbl.Columns[i].Name]; ok {
+			tbl.Columns[i].IsNotNull = notNull
+		}
+	}
+
 	schema.Tables = append(schema.Tables, &tbl)
 	return nil
 }