remove incomplete mysql and cockroachdb support

storage/sql/sql.go

@@ -6,11 +6,9 @@ import (
 	"regexp"
 	"time"
 
-	"github.com/cockroachdb/cockroach-go/crdb"
 	"github.com/sirupsen/logrus"
 
 	// import third party drivers
-	_ "github.com/go-sql-driver/mysql"
 	_ "github.com/lib/pq"
 	_ "github.com/mattn/go-sqlite3"
 )
@@ -21,13 +19,7 @@ import (
 type flavor struct {
 	queryReplacers []replacer
 
-	// Optional function to create and finish a transaction. This is mainly for
-	// cockroachdb support which requires special retry logic provided by their
-	// client package.
-	//
-	// This will be nil for most flavors.
-	//
-	// See: https://github.com/cockroachdb/docs/blob/63761c2e/_includes/app/txn-sample.go#L41-L44
+	// Optional function to create and finish a transaction.
 	executeTx func(db *sql.DB, fn func(*sql.Tx) error) error
 
 	// Does the flavor support timezones?
@@ -91,18 +83,6 @@ var (
 			{regexp.MustCompile(`\bnow\(\)`), "date('now')"},
 		},
 	}
-
-	// Incomplete.
-	flavorMySQL = flavor{
-		queryReplacers: []replacer{
-			{bindRegexp, "?"},
-		},
-	}
-
-	// Not tested.
-	flavorCockroach = flavor{
-		executeTx: crdb.ExecuteTx,
-	}
 )
 
 func (f flavor) translate(query string) string {