Cockroach delete limit (#697)

* DELETE FROM must have LIMIT support

CockroachDB is not able to deal well with massive deletes and their recommended approach is to batch delete statements. Thus, support for LIMIT statement is a must in the adapter.

* Updated tests

Author: jgirtakovskis

adapter/cockroachdb/template.go

@@ -123,6 +123,9 @@ const (
     DELETE
       FROM {{.Table | compile}}
       {{.Where | compile}}
+      {{if .Limit}}
+        LIMIT {{.Limit}}
+      {{end}}
   `
 	adapterUpdateLayout = `
     UPDATE

adapter/cockroachdb/template_test.go

@@ -259,4 +259,9 @@ func TestTemplateDelete(t *testing.T) {
 		`DELETE FROM "artist" WHERE (id > 5)`,
 		b.DeleteFrom("artist").Where("id > 5").String(),
 	)
+
+	assert.Equal(
+		`DELETE FROM "artist" WHERE (id > 5) LIMIT 10`,
+		b.DeleteFrom("artist").Where("id > 5").Limit(10).String(),
+	)
 }