hasher := h.pool.Get().(hash.Hash)
	h.borrowed = append(h.borrowed, hasher)
	hasher.Reset()
	return hasher
}

// ReturnAll will return all borrowed hashes.
func (h *HashBorrower) ReturnAll() {
	for _, hasher := range h.borrowed {
		h.pool.Put(hasher)
	}
	h.borrowed = nil
}

// StandardClaims are basically standard claims with "accessKey"
type StandardClaims struct {
	AccessKey string `json:"accessKey,omitempty"`

// Instances should be treated idempotent and not change once created.
type JSONPath struct {
	BaseKey  *Identifier        `parser:" @@"`
	PathExpr []*JSONPathElement `parser:"(@@)*"`

	// Cached values:
	pathString         string
	strippedTableAlias string
	strippedPathExpr   []*JSONPathElement
}

// AliasedExpression is an expression that can be optionally named
type AliasedExpression struct {