Add gorm annotations for fixed hex string length

Signed-off-by: Jim Zhang <[email protected]>

zkp/golang/pkg/core/storage.go

@@ -57,17 +57,17 @@ type SMTRoot struct {
 	Name string `gorm:"primaryKey"`
 	// this must be the hex bytes of the root index
 	// following the big-endian encoding
-	RootIndex string `gorm:"type:text"`
+	RootIndex string `gorm:"size:64"`
 }
 
 // SMTNode is the structure of a node in the merkle tree.
 // It only captures the reference key and the index of the node.
 // The value properties of a node are local states that are
 // handled outside of the merkle tree library.
 type SMTNode struct {
-	RefKey     string `gorm:"primaryKey"`
+	RefKey     string `gorm:"primaryKey;size:64"`
 	Type       byte
-	Index      *string // only leaf nodes have an index
-	LeftChild  *string // only branch nodes have children
-	RightChild *string
+	Index      *string `gorm:"size:64"` // only leaf nodes have an index
+	LeftChild  *string `gorm:"size:64"` // only branch nodes have children
+	RightChild *string `gorm:"size:64"`
 }