Detects nullable fields with LEFT_JOIN, OUTER_JOIN, or RIGHT_JOIN

- Builds on top of #733
- Properly detects left, right, full joins
- Uses proper enum ordering

Author: ryad-lindner

examples/booktest/postgresql/db_test.go

@@ -139,7 +139,7 @@ func TestBooks(t *testing.T) {
 		t.Fatal(err)
 	}
 	for _, ab := range res {
-		t.Logf("Book %d: '%s', Author: '%s', ISBN: '%s' Tags: '%v'\n", ab.BookID, ab.Title, ab.Name, ab.Isbn, ab.Tags)
+		t.Logf("Book %d: '%s', Author: '%s', ISBN: '%s' Tags: '%v'\n", ab.BookID, ab.Title, ab.Name.String, ab.Isbn, ab.Tags)
 	}
 
 	// TODO: call say_hello(varchar)

examples/booktest/postgresql/query.sql.go

@@ -23,7 +23,7 @@ WHERE tags && ?::varchar[]
 data class BooksByTagsRow (
   val bookId: Int,
   val title: String,
-  val name: String,
+  val name: String?,
   val isbn: String,
   val tags: List<String>
 )

examples/kotlin/src/main/kotlin/com/example/booktest/postgresql/QueriesImpl.kt

@@ -27,7 +27,7 @@
 class BooksByTagsRow:
     book_id: int
     title: str
-    name: str
+    name: Optional[str]
     isbn: str
     tags: List[str]
 

examples/python/src/booktest/query.py

@@ -206,9 +206,57 @@ func outputColumns(qc *QueryCatalog, node ast.Node) ([]*Column, error) {
 		}
 	}
 
+	if n, ok := node.(*ast.SelectStmt); ok {
+		for _, col := range cols {
+			if !col.NotNull || col.Table == nil {
+				continue
+			}
+			for _, f := range n.FromClause.Items {
+				if res := isCollNotNull(f, col.Table.Name, colNotNull); res != colNotFound {
+					col.NotNull = res == colNotNull
+					break
+				}
+			}
+		}
+	}
+
 	return cols, nil
 }
 
+const (
+	colNotFound = iota
+	colNotNull
+	colNull
+)
+
+func isCollNotNull(n ast.Node, tableName string, prior int) int {
+	switch n := n.(type) {
+	case *ast.RangeVar:
+		if *n.Relname == tableName {
+			return prior
+		}
+	case *ast.JoinExpr:
+		helper := func(l, r int) int {
+			if res := isCollNotNull(n.Larg, tableName, l); res != colNotFound {
+				return res
+			}
+			if res := isCollNotNull(n.Rarg, tableName, r); res != colNotFound {
+				return res
+			}
+			return colNotFound
+		}
+		switch n.Jointype {
+		case ast.JoinTypeLeft:
+			return helper(colNotNull, colNull)
+		case ast.JoinTypeRight:
+			return helper(colNull, colNotNull)
+		case ast.JoinTypeFull:
+			return helper(colNull, colNull)
+		}
+	}
+	return colNotFound
+}
+
 // Compute the output columns for a statement.
 //
 // Return an error if column references are ambiguous

internal/compiler/output_columns.go

@@ -0,0 +1,8 @@
+CREATE TABLE foo (id serial not null, bar_id int references bar(id));
+CREATE TABLE bar (id serial not null);
+
+-- name: NullableJoin :many
+SELECT f.id, f.bar_id, b.id
+FROM foo f
+FULL OUTER JOIN bar b ON b.id = f.bar_id
+WHERE f.id = $1;

internal/endtoend/testdata/join_nullable/mysql/go/db.go

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