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package gorm
import (
"errors"
"fmt"
"reflect"
"strconv"
"strings"
)
// preloadCallback used to preload associations
func preloadCallback(scope *Scope) {
if _, skip := scope.InstanceGet("gorm:skip_query_callback"); skip {
return
}
if ap, ok := scope.Get("gorm:auto_preload"); ok {
// If gorm:auto_preload IS NOT a bool then auto preload.
// Else if it IS a bool, use the value
if apb, ok := ap.(bool); !ok {
autoPreload(scope)
} else if apb {
autoPreload(scope)
}
}
if scope.Search.preload == nil || scope.HasError() {
return
}
var (
preloadedMap = map[string]bool{}
fields = scope.Fields()
)
for _, preload := range scope.Search.preload {
var (
preloadFields = strings.Split(preload.schema, ".")
currentScope = scope
currentFields = fields
)
for idx, preloadField := range preloadFields {
var currentPreloadConditions []interface{}
if currentScope == nil {
continue
}
// if not preloaded
if preloadKey := strings.Join(preloadFields[:idx+1], "."); !preloadedMap[preloadKey] {
// assign search conditions to last preload
if idx == len(preloadFields)-1 {
currentPreloadConditions = preload.conditions
}
for _, field := range currentFields {
if field.Name != preloadField || field.Relationship == nil {
continue
}
switch field.Relationship.Kind {
case "has_one":
currentScope.handleHasOnePreload(field, currentPreloadConditions)
case "has_many":
currentScope.handleHasManyPreload(field, currentPreloadConditions)
case "belongs_to":
currentScope.handleBelongsToPreload(field, currentPreloadConditions)
case "many_to_many":
currentScope.handleManyToManyPreload(field, currentPreloadConditions)
default:
scope.Err(errors.New("unsupported relation"))
}
preloadedMap[preloadKey] = true
break
}
if !preloadedMap[preloadKey] {
scope.Err(fmt.Errorf("can't preload field %s for %s", preloadField, currentScope.GetModelStruct().ModelType))
return
}
}
// preload next level
if idx < len(preloadFields)-1 {
currentScope = currentScope.getColumnAsScope(preloadField)
if currentScope != nil {
currentFields = currentScope.Fields()
}
}
}
}
}
func autoPreload(scope *Scope) {
for _, field := range scope.Fields() {
if field.Relationship == nil {
continue
}
if val, ok := field.TagSettingsGet("PRELOAD"); ok {
if preload, err := strconv.ParseBool(val); err != nil {
scope.Err(errors.New("invalid preload option"))
return
} else if !preload {
continue
}
}
scope.Search.Preload(field.Name)
}
}
func (scope *Scope) generatePreloadDBWithConditions(conditions []interface{}) (*DB, []interface{}) {
var (
preloadDB = scope.NewDB()
preloadConditions []interface{}
)
for _, condition := range conditions {
if scopes, ok := condition.(func(*DB) *DB); ok {
preloadDB = scopes(preloadDB)
} else {
preloadConditions = append(preloadConditions, condition)
}
}
return preloadDB, preloadConditions
}
// handleHasOnePreload used to preload has one associations
func (scope *Scope) handleHasOnePreload(field *Field, conditions []interface{}) {
relation := field.Relationship
// get relations's primary keys
primaryKeys := scope.getColumnAsArray(relation.AssociationForeignFieldNames, scope.Value)
if len(primaryKeys) == 0 {
return
}
// preload conditions
preloadDB, preloadConditions := scope.generatePreloadDBWithConditions(conditions)
// find relations
query := fmt.Sprintf("%v IN (%v)", toQueryCondition(scope, relation.ForeignDBNames), toQueryMarks(primaryKeys))
values := toQueryValues(primaryKeys)
if relation.PolymorphicType != "" {
query += fmt.Sprintf(" AND %v = ?", scope.Quote(relation.PolymorphicDBName))
values = append(values, relation.PolymorphicValue)
}
results := makeSlice(field.Struct.Type)
scope.Err(preloadDB.Where(query, values...).Find(results, preloadConditions...).Error)
// assign find results
var (
resultsValue = indirect(reflect.ValueOf(results))
indirectScopeValue = scope.IndirectValue()
)
if indirectScopeValue.Kind() == reflect.Slice {
foreignValuesToResults := make(map[string]reflect.Value)
for i := 0; i < resultsValue.Len(); i++ {
result := resultsValue.Index(i)
foreignValues := toString(getValueFromFields(result, relation.ForeignFieldNames))
foreignValuesToResults[foreignValues] = result
}
for j := 0; j < indirectScopeValue.Len(); j++ {
indirectValue := indirect(indirectScopeValue.Index(j))
valueString := toString(getValueFromFields(indirectValue, relation.AssociationForeignFieldNames))
if result, found := foreignValuesToResults[valueString]; found {
indirectValue.FieldByName(field.Name).Set(result)
}
}
} else {
for i := 0; i < resultsValue.Len(); i++ {
result := resultsValue.Index(i)
scope.Err(field.Set(result))
}
}
}
// handleHasManyPreload used to preload has many associations
func (scope *Scope) handleHasManyPreload(field *Field, conditions []interface{}) {
relation := field.Relationship
// get relations's primary keys
primaryKeys := scope.getColumnAsArray(relation.AssociationForeignFieldNames, scope.Value)
if len(primaryKeys) == 0 {
return
}
// preload conditions
preloadDB, preloadConditions := scope.generatePreloadDBWithConditions(conditions)
// find relations
query := fmt.Sprintf("%v IN (%v)", toQueryCondition(scope, relation.ForeignDBNames), toQueryMarks(primaryKeys))
values := toQueryValues(primaryKeys)
if relation.PolymorphicType != "" {
query += fmt.Sprintf(" AND %v = ?", scope.Quote(relation.PolymorphicDBName))
values = append(values, relation.PolymorphicValue)
}
results := makeSlice(field.Struct.Type)
scope.Err(preloadDB.Where(query, values...).Find(results, preloadConditions...).Error)
// assign find results
var (
resultsValue = indirect(reflect.ValueOf(results))
indirectScopeValue = scope.IndirectValue()
)
if indirectScopeValue.Kind() == reflect.Slice {
preloadMap := make(map[string][]reflect.Value)
for i := 0; i < resultsValue.Len(); i++ {
result := resultsValue.Index(i)
foreignValues := getValueFromFields(result, relation.ForeignFieldNames)
preloadMap[toString(foreignValues)] = append(preloadMap[toString(foreignValues)], result)
}
for j := 0; j < indirectScopeValue.Len(); j++ {
object := indirect(indirectScopeValue.Index(j))
objectRealValue := getValueFromFields(object, relation.AssociationForeignFieldNames)
f := object.FieldByName(field.Name)
if results, ok := preloadMap[toString(objectRealValue)]; ok {
f.Set(reflect.Append(f, results...))
} else {
f.Set(reflect.MakeSlice(f.Type(), 0, 0))
}
}
} else {
scope.Err(field.Set(resultsValue))
}
}
// handleBelongsToPreload used to preload belongs to associations
func (scope *Scope) handleBelongsToPreload(field *Field, conditions []interface{}) {
relation := field.Relationship
// preload conditions
preloadDB, preloadConditions := scope.generatePreloadDBWithConditions(conditions)
// get relations's primary keys
primaryKeys := scope.getColumnAsArray(relation.ForeignFieldNames, scope.Value)
if len(primaryKeys) == 0 {
return
}
// find relations
results := makeSlice(field.Struct.Type)
scope.Err(preloadDB.Where(fmt.Sprintf("%v IN (%v)", toQueryCondition(scope, relation.AssociationForeignDBNames), toQueryMarks(primaryKeys)), toQueryValues(primaryKeys)...).Find(results, preloadConditions...).Error)
// assign find results
var (
resultsValue = indirect(reflect.ValueOf(results))
indirectScopeValue = scope.IndirectValue()
)
foreignFieldToObjects := make(map[string][]*reflect.Value)
if indirectScopeValue.Kind() == reflect.Slice {
for j := 0; j < indirectScopeValue.Len(); j++ {
object := indirect(indirectScopeValue.Index(j))
valueString := toString(getValueFromFields(object, relation.ForeignFieldNames))
foreignFieldToObjects[valueString] = append(foreignFieldToObjects[valueString], &object)
}
}
for i := 0; i < resultsValue.Len(); i++ {
result := resultsValue.Index(i)
if indirectScopeValue.Kind() == reflect.Slice {
valueString := toString(getValueFromFields(result, relation.AssociationForeignFieldNames))
if objects, found := foreignFieldToObjects[valueString]; found {
for _, object := range objects {
object.FieldByName(field.Name).Set(result)
}
}
} else {
scope.Err(field.Set(result))
}
}
}
// handleManyToManyPreload used to preload many to many associations
func (scope *Scope) handleManyToManyPreload(field *Field, conditions []interface{}) {
var (
relation = field.Relationship
joinTableHandler = relation.JoinTableHandler
fieldType = field.Struct.Type.Elem()
foreignKeyValue interface{}
foreignKeyType = reflect.ValueOf(&foreignKeyValue).Type()
linkHash = map[string][]reflect.Value{}
isPtr bool
)
if fieldType.Kind() == reflect.Ptr {
isPtr = true
fieldType = fieldType.Elem()
}
var sourceKeys = []string{}
for _, key := range joinTableHandler.SourceForeignKeys() {
sourceKeys = append(sourceKeys, key.DBName)
}
// preload conditions
preloadDB, preloadConditions := scope.generatePreloadDBWithConditions(conditions)
// generate query with join table
newScope := scope.New(reflect.New(fieldType).Interface())
preloadDB = preloadDB.Table(newScope.TableName()).Model(newScope.Value)
if len(preloadDB.search.selects) == 0 {
preloadDB = preloadDB.Select("*")
}
preloadDB = joinTableHandler.JoinWith(joinTableHandler, preloadDB, scope.Value)
// preload inline conditions
if len(preloadConditions) > 0 {
preloadDB = preloadDB.Where(preloadConditions[0], preloadConditions[1:]...)
}
rows, err := preloadDB.Rows()
if scope.Err(err) != nil {
return
}
defer rows.Close()
columns, _ := rows.Columns()
for rows.Next() {
var (
elem = reflect.New(fieldType).Elem()
fields = scope.New(elem.Addr().Interface()).Fields()
)
// register foreign keys in join tables
var joinTableFields []*Field
for _, sourceKey := range sourceKeys {
joinTableFields = append(joinTableFields, &Field{StructField: &StructField{DBName: sourceKey, IsNormal: true}, Field: reflect.New(foreignKeyType).Elem()})
}
scope.scan(rows, columns, append(fields, joinTableFields...))
scope.New(elem.Addr().Interface()).
InstanceSet("gorm:skip_query_callback", true).
callCallbacks(scope.db.parent.callbacks.queries)
var foreignKeys = make([]interface{}, len(sourceKeys))
// generate hashed forkey keys in join table
for idx, joinTableField := range joinTableFields {
if !joinTableField.Field.IsNil() {
foreignKeys[idx] = joinTableField.Field.Elem().Interface()
}
}
hashedSourceKeys := toString(foreignKeys)
if isPtr {
linkHash[hashedSourceKeys] = append(linkHash[hashedSourceKeys], elem.Addr())
} else {
linkHash[hashedSourceKeys] = append(linkHash[hashedSourceKeys], elem)
}
}
if err := rows.Err(); err != nil {
scope.Err(err)
}
// assign find results
var (
indirectScopeValue = scope.IndirectValue()
fieldsSourceMap = map[string][]reflect.Value{}
foreignFieldNames = []string{}
)
for _, dbName := range relation.ForeignFieldNames {
if field, ok := scope.FieldByName(dbName); ok {
foreignFieldNames = append(foreignFieldNames, field.Name)
}
}
if indirectScopeValue.Kind() == reflect.Slice {
for j := 0; j < indirectScopeValue.Len(); j++ {
object := indirect(indirectScopeValue.Index(j))
key := toString(getValueFromFields(object, foreignFieldNames))
fieldsSourceMap[key] = append(fieldsSourceMap[key], object.FieldByName(field.Name))
}
} else if indirectScopeValue.IsValid() {
key := toString(getValueFromFields(indirectScopeValue, foreignFieldNames))
fieldsSourceMap[key] = append(fieldsSourceMap[key], indirectScopeValue.FieldByName(field.Name))
}
for source, link := range linkHash {
for i, field := range fieldsSourceMap[source] {
//If not 0 this means Value is a pointer and we already added preloaded models to it
if fieldsSourceMap[source][i].Len() != 0 {
continue
}
field.Set(reflect.Append(fieldsSourceMap[source][i], link...))
}
}
}