Stop using pointers for OpCreateIndex fields (#565)

Set JSON schema defaults for the optional fields in `OpCreateIndex` so
that the generated types don't use pointers.

This simplifies the use of those fields.

pkg/migrations/op_create_index.go

@@ -20,27 +20,27 @@ func (o *OpCreateIndex) Start(ctx context.Context, conn db.DB, latestSchema stri
 
 	// create index concurrently
 	stmtFmt := "CREATE INDEX CONCURRENTLY %s ON %s"
-	if o.Unique != nil && *o.Unique {
+	if o.Unique {
 		stmtFmt = "CREATE UNIQUE INDEX CONCURRENTLY %s ON %s"
 	}
 	stmt := fmt.Sprintf(stmtFmt,
 		pq.QuoteIdentifier(o.Name),
 		pq.QuoteIdentifier(table.Name))
 
-	if o.Method != nil {
-		stmt += fmt.Sprintf(" USING %s", string(*o.Method))
+	if o.Method != "" {
+		stmt += fmt.Sprintf(" USING %s", string(o.Method))
 	}
 
 	stmt += fmt.Sprintf(" (%s)", strings.Join(
 		quoteColumnNames(table.PhysicalColumnNamesFor(o.Columns...)), ", "),
 	)
 
-	if o.StorageParameters != nil {
-		stmt += fmt.Sprintf(" WITH (%s)", *o.StorageParameters)
+	if o.StorageParameters != "" {
+		stmt += fmt.Sprintf(" WITH (%s)", o.StorageParameters)
 	}
 
-	if o.Predicate != nil {
-		stmt += fmt.Sprintf(" WHERE %s", *o.Predicate)
+	if o.Predicate != "" {
+		stmt += fmt.Sprintf(" WHERE %s", o.Predicate)
 	}
 
 	_, err := conn.ExecContext(ctx, stmt)

pkg/migrations/op_create_index_test.go

@@ -143,7 +143,7 @@ func TestCreateIndex(t *testing.T) {
 							Name:      "idx_users_name_after_2019",
 							Table:     "users",
 							Columns:   []string{"registered_at_year"},
-							Predicate: ptr("registered_at_year > 2019"),
+							Predicate: "registered_at_year > 2019",
 						},
 					},
 				},
@@ -235,8 +235,8 @@ func TestCreateIndex(t *testing.T) {
 							Name:              "idx_users_name_hash",
 							Table:             "users",
 							Columns:           []string{"name"},
-							Method:            ptr(migrations.OpCreateIndexMethodHash),
-							StorageParameters: ptr("fillfactor = 70"),
+							Method:            migrations.OpCreateIndexMethodHash,
+							StorageParameters: "fillfactor = 70",
 						},
 					},
 				},

schema.json

@@ -238,20 +238,24 @@
         },
         "predicate": {
           "description": "Conditional expression for defining a partial index",
-          "type": "string"
+          "type": "string",
+          "default": ""
         },
         "method": {
           "description": "Index method to use for the index: btree, hash, gist, spgist, gin, brin",
           "type": "string",
-          "enum": ["btree", "hash", "gist", "spgist", "gin", "brin"]
+          "enum": ["btree", "hash", "gist", "spgist", "gin", "brin"],
+          "default": "btree"
         },
         "storage_parameters": {
           "description": "Storage parameters for the index",
-          "type": "string"
+          "type": "string",
+          "default": ""
         },
         "unique": {
           "description": "Indicates if the index is unique",
-          "type": "boolean"
+          "type": "boolean",
+          "default": false
         }
       },
       "required": ["columns", "name", "table"],