Fix issue with detecting many to many relationships

psql/schema.go

@@ -66,7 +66,14 @@ func NewDBSchema(info *DBInfo, aliases map[string][]string) (*DBSchema, error) {
 	}
 
 	for i, t := range info.Tables {
-		err := schema.updateRelationships(t, info.Columns[i])
+		err := schema.firstDegreeRels(t, info.Columns[i])
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	for i, t := range info.Tables {
+		err := schema.secondDegreeRels(t, info.Columns[i])
 		if err != nil {
 			return nil, err
 		}
@@ -131,8 +138,7 @@ func (s *DBSchema) addTable(
 	return nil
 }
 
-func (s *DBSchema) updateRelationships(t DBTable, cols []DBColumn) error {
-	jcols := make([]DBColumn, 0, len(cols))
+func (s *DBSchema) firstDegreeRels(t DBTable, cols []DBColumn) error {
 	ct := t.Key
 	cti, ok := s.t[ct]
 	if !ok {
@@ -230,6 +236,51 @@ func (s *DBSchema) updateRelationships(t DBTable, cols []DBColumn) error {
 		if err := s.SetRel(ft, ct, rel2); err != nil {
 			return err
 		}
+	}
+
+	return nil
+}
+
+func (s *DBSchema) secondDegreeRels(t DBTable, cols []DBColumn) error {
+	jcols := make([]DBColumn, 0, len(cols))
+	ct := t.Key
+	cti, ok := s.t[ct]
+	if !ok {
+		return fmt.Errorf("invalid foreign key table '%s'", ct)
+	}
+
+	for i := range cols {
+		c := cols[i]
+
+		if len(c.FKeyTable) == 0 {
+			continue
+		}
+
+		// Foreign key column name
+		ft := strings.ToLower(c.FKeyTable)
+
+		ti, ok := s.t[ft]
+		if !ok {
+			return fmt.Errorf("invalid foreign key table '%s'", ft)
+		}
+
+		// This is an embedded relationship like when a json/jsonb column
+		// is exposed as a table
+		if c.Name == c.FKeyTable && len(c.FKeyColID) == 0 {
+			continue
+		}
+
+		if len(c.FKeyColID) == 0 {
+			continue
+		}
+
+		// Foreign key column id
+		fcid := c.FKeyColID[0]
+
+		if _, ok := ti.ColIDMap[fcid]; !ok {
+			return fmt.Errorf("invalid foreign key column id '%d' for table '%s'",
+				fcid, ti.Name)
+		}
 
 		jcols = append(jcols, c)
 	}
@@ -322,6 +373,9 @@ func (s *DBSchema) GetTable(table string) (*DBTableInfo, error) {
 }
 
 func (s *DBSchema) SetRel(child, parent string, rel *DBRel) error {
+	sp := strings.ToLower(flect.Singularize(parent))
+	pp := strings.ToLower(flect.Pluralize(parent))
+
 	sc := strings.ToLower(flect.Singularize(child))
 	pc := strings.ToLower(flect.Pluralize(child))
 
@@ -333,9 +387,6 @@ func (s *DBSchema) SetRel(child, parent string, rel *DBRel) error {
 		s.rm[pc] = make(map[string]*DBRel)
 	}
 
-	sp := strings.ToLower(flect.Singularize(parent))
-	pp := strings.ToLower(flect.Pluralize(parent))
-
 	if _, ok := s.rm[sc][sp]; !ok {
 		s.rm[sc][sp] = rel
 	}

psql/strings.go

@@ -19,6 +19,10 @@ func (rt RelType) String() string {
 }
 
 func (re *DBRel) String() string {
+	if re.Type == RelOneToManyThrough {
+		return fmt.Sprintf("'%s.%s' --(Through: %s)--> '%s.%s'",
+			re.Left.Table, re.Left.Col, re.Through, re.Right.Table, re.Right.Col)
+	}
 	return fmt.Sprintf("'%s.%s' --(%s)--> '%s.%s'",
 		re.Left.Table, re.Left.Col, re.Type, re.Right.Table, re.Right.Col)
 }

psql/test_schema.go

@@ -92,7 +92,14 @@ func getTestSchema() *DBSchema {
 	}
 
 	for i, t := range tables {
-		err := schema.updateRelationships(t, columns[i])
+		err := schema.firstDegreeRels(t, columns[i])
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+
+	for i, t := range tables {
+		err := schema.secondDegreeRels(t, columns[i])
 		if err != nil {
 			log.Fatal(err)
 		}