目录
- 1、思路
- 2、实验
- 3、总结
1、思路
一个field的设置是不能被修改的，如果要修改一个Field，那么应该重新按照新的mapping，建立一个index_new，然后将数据批量查询出来，重新用bulk api写入index_new中批量查询的时候，建议采用scroll api，并且采用多线程并发的方式来reindex数据，每次scoll就查询指定日期的一段数据，交给一个线程即可，当数据导入index_new完毕时，客户端在切换到新的index_new即可。
2、实验
（1）一开始，依靠dynamic mapping，插入数据，但是不小心有些数据是2017-01-01这种日期格式的，所以title这种field被自动映射为了【date】类型，实际上它应该是【string】类型的。
导入数据
PUT /my_index/my_type/1
{
"title":"2019-01-01"
}
PUT /my_index/my_type/2
{
"title":"2019-01-02"
}
PUT /my_index/my_type/3
{
"title":"2019-01-03"
}
查看mapping 类型
get /my_index/_mapping/my_type
{
"my_index": {
"mappings": {
"my_type": {
"properties": {
"title": {
"type": "date"
}
}
}
}
}
}
（2）当后期向索引中加入string类型的title值的时候，就会报错
插入数据
PUT /my_index/my_type/4
{
"title":"hello elasticsearch"
}
反馈结果
{
"error": {
"root_cause": [
{
"type": "mapper_parsing_exception",
"reason": "failed to parse [title]"
}
],
"type": "mapper_parsing_exception",
"reason": "failed to parse [title]",
"caused_by": {
"type": "illegal_argument_exception",
"reason": "Invalid format: \"hello elasticsearch\""
}
},
"status": 400
}
（3）如果此时想修改title的类型，是不可能的
PUT /my_index/_mapping/my_type
{
"properties": {
"title":{
"type": "text"
}
}
}
反馈信息
{
"error": {
"root_cause": [
{
"type": "illegal_argument_exception",
"reason": "mapper [title] of different type, current_type [date], merged_type [text]"
}
],
"type": "illegal_argument_exception",
"reason": "mapper [title] of different type, current_type [date], merged_type [text]"
},
"status": 400
}
（4）此时，唯一的办法，就是进行reindex，也就是说，重新建立一个索引，将旧索引的数据查询出来，再导入新索引
（5）如果说旧索引的名字，是old_index，新索引的名字是new_index，终端java应用，已经在使用old_index在操作了，难道还要去停止java应用，修改使用的index为new_index，才重新启动java应用吗？这个过程中，就会导致java应用停机，可用性降低
（6）所以说，给java应用一个别名，这个别名是指向旧索引的，java应用先用着，java应用先用goods_index alias来操作，此时实际指向的是旧的my_index
PUT /my_index/_alias/goods_index
反馈信息
{
"acknowledged": true
}
（7）新建一个index，调整其title的类型为string
PUT /my_index_new
{
"mappings": {
"my_type":{
"properties": {
"title":{
"type": "text"
}
}
}
}
}
（8）使用scroll api将数据批量查询出来,
实例查询一条即可：
GET /my_index/_search?scroll=1m
{
"query": {
"match_all": {}
},
"sort": ["_doc"],
"size": 1
}
反馈信息
{
"_scroll_id": "DnF1ZXJ5VGhlbkZldGNoBQAAAAAAAAO5Fm1vRkdXOXJzU2VxaVRaaXBsLXZvZlEAAAAAAAADuhZtb0ZHVzlyc1NlcWlUWmlwbC12b2ZRAAAAAAAAA7cWbW9GR1c5cnNTZXFpVFppcGwtdm9mUQAAAAAAAAO7Fm1vRkdXOXJzU2VxaVRaaXBsLXZvZlEAAAAAAAADuBZtb0ZHVzlyc1NlcWlUWmlwbC12b2ZR",
"took": 3,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 3,
"max_score": null,
"hits": [
{
"_index": "my_index",
"_type": "my_type",
"_id": "2",
"_score": null,
"_source": {
"title": "2019-01-02"
},
"sort": [
]
}
]
}
}
（9）采用bulk api将scoll查出来的一批数据，批量写入新索引
POST /_bulk
{ "index": { "_index": "my_index_new", "_type": "my_type", "_id": "2" }}
{ "title": "2017-01-02" }
反馈信息
{
"took": 2161,
"errors": false,
"items": [
{
"index": {
"_index": "my_index_new",
"_type": "my_type",
"_id": "2",
"_version": 1,
"result": "created",
"_shards": {
"total": 2,
"successful": 1,
"failed": 0
},
"created": true,
"status": 201
}
}
]
}
（10）反复循环8~9，查询一批又一批的数据出来，采取bulk api将每一批数据批量写入新索引
（11）将goods_index alias切换到my_index_new上去，java应用会直接通过index别名使用新的索引中的数据，java应用程序不需要停机，零提交，高可用
POST /_aliases
{
"actions": [
{ "remove": { "index": "my_index", "alias": "goods_index" }},
{ "add": { "index": "my_index_new", "alias": "goods_index" }}
]
}
反馈信息
{
"acknowledged": true
}
（12）直接通过goods_index别名来查询，是否ok
GET /goods_index/my_type/_search
{
"query": {
"match_all": {}
}
}
反馈信息：
{
"took": 1,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 1,
"max_score": 1,
"hits": [
{
"_index": "my_index_new",
"_type": "my_type",
"_id": "2",
"_score": 1,
"_source": {
"title": "2017-01-02"
}
}
]
}
}
查看新的index 的 type类型
GET /goods_index/_mapping/my_type
{
"my_index_new": {
"mappings": {
"my_type": {
"properties": {
"title": {
"type": "text"
}
}
}
}
}
}
插入string类型的数据
PUT /goods_index/my_type/6
{
"title":"hello elasticsearch"
}
反馈信息
{
"_index": "my_index_new",
"_type": "my_type",
"_id": "6",
"_version": 1,
"result": "created",
"_shards": {
"total": 2,
"successful": 1,
"failed": 0
},
"created": true
}
查询所有信息
GET /goods_index/my_type/_search
{
"query": {
"match_all": {}
}
}
反馈信息
{
"took": 2,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 2,
"max_score": 1,
"hits": [
{
"_index": "my_index_new",
"_type": "my_type",
"_id": "2",
"_score": 1,
"_source": {
"title": "2017-01-02"
}
},
{
"_index": "my_index_new",
"_type": "my_type",
"_id": "6",
"_score": 1,
"_source": {
"title": "hello elasticsearch"
}
}
]
}
}
3、总结
string 类型数据 可以 添加到新的index在中，并且原来的信息已经导入（本次实例导入原来的一条数据）
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