xref #198

In our scenario, predicate matches in a hot path and causes performance problems. the cost of reflect.ValueOf(c.predicate).Call([]reflect.Value{reflect.ValueOf(m)}) is quite expensive.

The predicate is expected to be like func (model.Model) bool Eg func (lsp *LogicalSwitchPort) bool { return lsp.Name == "lorem" }. We are trying to eliminate the reflect here. Any suggestions?

// matches returns the result of the execution of the predicate
// Type verifications are not performed
// Returns the models that match the conditions
func (c *predicateConditional) Matches() (map[string]model.Model, error) {
...
	for u, m := range tableCache.RowsShallow() {
		// very expensive and reflect.Value.Call could not cache funcLayout
 ==>		ret := reflect.ValueOf(c.predicate).Call([]reflect.Value{reflect.ValueOf(m)})
		if ret[0].Bool() {
			found[u] = model.Clone(m)
		}
	}
	return found, nil
}

https://github.com/ovn-org/libovsdb/blob/main/client/condition.go#L194-L197

I suppose we could change client API

// Create a Conditional API from a Function that is used to filter cached data
// The function must accept a Model implementation and return a boolean. E.g:
// ConditionFromFunc(func(l *LogicalSwitch) bool { return l.Enabled })
WhereCache(predicate interface{}) ConditionalAPI

to

// Create a Conditional API from a Function that is used to filter cached data
// The function must accept a Model implementation and return a boolean. E.g:
// ConditionFromFunc(func(l *LogicalSwitch) bool { return l.Enabled })
WhereCache(predicate func(model.Model)bool) ConditionalAPI

And model API, GetTableName function could add to modelgen tmpl. To get the table name from the predicate

// Conditional interface implementation
// FromFunc returns a Condition from a function
func (a api) conditionFromFunc(predicate interface{}) Conditional {
==>	table, err := a.getTableFromFunc(predicate)
	if err != nil {
		return newErrorConditional(err)
	}

	condition, err := newPredicateConditional(table, a.cache, predicate)
	if err != nil {
		return newErrorConditional(err)
	}
	return condition
}

//type MyLogicalRouter struct {
//	UUID          string            `ovsdb:"_uuid"`
//	Name          string            `ovsdb:"name"`
//	ExternalIDs   map[string]string `ovsdb:"external_ids"`
//	LoadBalancers []string          `ovsdb:"load_balancer"`
//}
type Model interface{}

to

//type MyLogicalRouter struct {
//	UUID          string            `ovsdb:"_uuid"`
//	Name          string            `ovsdb:"name"`
//	ExternalIDs   map[string]string `ovsdb:"external_ids"`
//	LoadBalancers []string          `ovsdb:"load_balancer"`
//}
type Model interface{
	GetTableName()string
}

Then Matches could refactor to

func (c *predicateConditional) Matches() (map[string]model.Model, error) {
...
	for u, m := range tableCache.RowsShallow() {
		if c.predicate(m) {
			found[u] = model.Clone(m)
		}
	}
	return found, nil
}

Edit:
According to the test file looks like there was a Table function in model.Model interface

//LogicalSwitchPort struct defines an object in Logical_Switch_Port table
type testLogicalSwitchPort struct {
	UUID             string            `ovsdb:"_uuid"`
	Up               *bool             `ovsdb:"up"`
	Dhcpv4Options    *string           `ovsdb:"dhcpv4_options"`
	Name             string            `ovsdb:"name"`
	DynamicAddresses *string           `ovsdb:"dynamic_addresses"`
	HaChassisGroup   *string           `ovsdb:"ha_chassis_group"`
	Options          map[string]string `ovsdb:"options"`
	Enabled          *bool             `ovsdb:"enabled"`
	Addresses        []string          `ovsdb:"addresses"`
	Dhcpv6Options    *string           `ovsdb:"dhcpv6_options"`
	TagRequest       *int              `ovsdb:"tag_request"`
	Tag              *int              `ovsdb:"tag"`
	PortSecurity     []string          `ovsdb:"port_security"`
	ExternalIds      map[string]string `ovsdb:"external_ids"`
	Type             string            `ovsdb:"type"`
	ParentName       *string           `ovsdb:"parent_name"`
}

// Table returns the table name. It's part of the Model interface
func (*testLogicalSwitchPort) Table() string {
	return "Logical_Switch_Port"
}