Simple and Powerful ORM for Go, support mysql,postgres,tidb,sqlite3,mssql,oracle https://xorm.io
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// Copyright 2016 The Xorm Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package xorm
import (
"reflect"
"xorm.io/xorm/internal/utils"
)
// IterFunc only use by Iterate
type IterFunc func(idx int, bean interface{}) error
// Rows return sql.Rows compatible Rows obj, as a forward Iterator object for iterating record by record, bean's non-empty fields
// are conditions.
func (session *Session) Rows(bean interface{}) (*Rows, error) {
return newRows(session, bean)
}
// Iterate record by record handle records from table, condiBeans's non-empty fields
// are conditions. beans could be []Struct, []*Struct, map[int64]Struct
// map[int64]*Struct
func (session *Session) Iterate(bean interface{}, fun IterFunc) error {
if session.isAutoClose {
defer session.Close()
}
if session.statement.LastError != nil {
return session.statement.LastError
}
if session.statement.BufferSize > 0 {
return session.bufferIterate(bean, fun)
}
rows, err := session.Rows(bean)
if err != nil {
return err
}
defer rows.Close()
i := 0
for rows.Next() {
b := reflect.New(rows.beanType).Interface()
err = rows.Scan(b)
if err != nil {
return err
}
err = fun(i, b)
if err != nil {
return err
}
i++
}
return err
}
// BufferSize sets the buffersize for iterate
func (session *Session) BufferSize(size int) *Session {
session.statement.BufferSize = size
return session
}
func (session *Session) bufferIterate(bean interface{}, fun IterFunc) error {
var bufferSize = session.statement.BufferSize
var pLimitN = session.statement.LimitN
if pLimitN != nil && bufferSize > *pLimitN {
bufferSize = *pLimitN
}
var start = session.statement.Start
v := utils.ReflectValue(bean)
sliceType := reflect.SliceOf(v.Type())
var idx = 0
session.autoResetStatement = false
defer func() {
session.autoResetStatement = true
}()
for bufferSize > 0 {
slice := reflect.New(sliceType)
if err := session.NoCache().Limit(bufferSize, start).find(slice.Interface(), bean); err != nil {
return err
}
for i := 0; i < slice.Elem().Len(); i++ {
if err := fun(idx, slice.Elem().Index(i).Addr().Interface()); err != nil {
return err
}
idx++
}
if bufferSize > slice.Elem().Len() {
break
}
start = start + slice.Elem().Len()
if pLimitN != nil && start+bufferSize > *pLimitN {
bufferSize = *pLimitN - start
}
}
return nil
}