refactor: distinguish between Unique and UniqueIndex (#195)

migrator.go

@@ -13,25 +13,28 @@ import (
  "gorm.io/gorm/schema"
 )
 
+// See https://stackoverflow.com/questions/2204058/list-columns-with-indexes-in-postgresql
+// Here are some changes:
+// - use `LEFT JOIN` instead of `CROSS JOIN`
+// - exclude indexes used to support constraints (they are auto-generated)
 const indexSql = `
-select
- t.relname as table_name,
- i.relname as index_name,
- a.attname as column_name,
- ix.indisunique as non_unique,
- ix.indisprimary as primary
-from
- pg_class t,
- pg_class i,
- pg_index ix,
- pg_attribute a
-where
- t.oid = ix.indrelid
- and i.oid = ix.indexrelid
- and a.attrelid = t.oid
- and a.attnum = ANY(ix.indkey)
- and t.relkind = 'r'
- and t.relname = ?
+SELECT
+ ct.relname AS table_name,
+ ci.relname AS index_name,
+ i.indisunique AS non_unique,
+ i.indisprimary AS primary,
+ a.attname AS column_name
+FROM
+ pg_index i
+ LEFT JOIN pg_class ct ON ct.oid = i.indrelid
+ LEFT JOIN pg_class ci ON ci.oid = i.indexrelid
+ LEFT JOIN pg_attribute a ON a.attrelid = ct.oid
+ LEFT JOIN pg_constraint con ON con.conindid = i.indexrelid
+WHERE
+ a.attnum = ANY(i.indkey)
+ AND con.oid IS NULL
+ AND ct.relkind = 'r'
+ AND ct.relname = ?
 `
 
 var typeAliasMap = map[string][]string{
@@ -347,16 +350,6 @@ func (m Migrator) AlterColumn(value interface{}, field string) error {
  }
  }
 
- if uniq, _ := fieldColumnType.Unique(); !uniq && field.Unique {
- idxName := clause.Column{Name: m.DB.Config.NamingStrategy.IndexName(stmt.Table, field.DBName)}
- // Not a unique constraint but a unique index
- if !m.HasIndex(stmt.Table, idxName.Name) {
- if err := m.DB.Exec("ALTER TABLE ? ADD CONSTRAINT ? UNIQUE(?)", m.CurrentTable(stmt), idxName, clause.Column{Name: field.DBName}).Error; err != nil {
- return err
- }
- }
- }
-
  if v, ok := fieldColumnType.DefaultValue(); (field.DefaultValueInterface == nil && ok) || v != field.DefaultValue {
  if field.HasDefaultValue && (field.DefaultValueInterface != nil || field.DefaultValue != "") {
  if field.DefaultValueInterface != nil {
@@ -415,13 +408,11 @@ func (m Migrator) modifyColumn(stmt *gorm.Statement, field *schema.Field, target
 func (m Migrator) HasConstraint(value interface{}, name string) bool {
  var count int64
  m.RunWithValue(value, func(stmt *gorm.Statement) error {
- constraint, chk, table := m.GuessConstraintAndTable(stmt, name)
- currentSchema, curTable := m.CurrentSchema(stmt, table)
+ constraint, table := m.GuessConstraintInterfaceAndTable(stmt, name)
  if constraint != nil {
- name = constraint.Name
- } else if chk != nil {
- name = chk.Name
+ name = constraint.GetName()
  }
+ currentSchema, curTable := m.CurrentSchema(stmt, table)
 
  return m.DB.Raw(
  "SELECT count(*) FROM INFORMATION_SCHEMA.table_constraints WHERE table_schema = ? AND table_name = ? AND constraint_name = ?",