目錄
- 1、思路
- 2、實驗
- 3、總結
1、思路
一個field的設定是不能被修改的，如果要修改一個Field，那麼應該重新按照新的mapping，建立一個index_new，然後将資料批量查詢出來，重新用bulk api寫入index_new中批量查詢的時候，建議采用scroll api，并且采用多線程并發的方式來reindex資料，每次scoll就查詢指定日期的一段資料，交給一個線程即可，當資料導入index_new完畢時，用戶端在切換到新的index_new即可。
2、實驗
（1）一開始，依靠dynamic mapping，插入資料，但是不小心有些資料是2017-01-01這種日期格式的，是以title這種field被自動映射為了【date】類型，實際上它應該是【string】類型的。
導入資料
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"
}
檢視mapping 類型
get /my_index/_mapping/my_type
{
"my_index": {
"mappings": {
"my_type": {
"properties": {
"title": {
"type": "date"
}
}
}
}
}
}
（2）當後期向索引中加入string類型的title值的時候，就會報錯
插入資料
PUT /my_index/my_type/4
{
"title":"hello elasticsearch"
}
回報結果
{
"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）如果此時想修改title的類型，是不可能的
PUT /my_index/_mapping/my_type
{
"properties": {
"title":{
"type": "text"
}
}
}
回報資訊
{
"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）此時，唯一的辦法，就是進行reindex，也就是說，重建立立一個索引，将舊索引的資料查詢出來，再導入新索引
（5）如果說舊索引的名字，是old_index，新索引的名字是new_index，終端java應用，已經在使用old_index在操作了，難道還要去停止java應用，修改使用的index為new_index，才重新啟動java應用嗎？這個過程中，就會導緻java應用停機，可用性降低
（6）是以說，給java應用一個别名，這個别名是指向舊索引的，java應用先用着，java應用先用goods_index alias來操作，此時實際指向的是舊的my_index
PUT /my_index/_alias/goods_index
回報資訊
{
"acknowledged": true
}
（7）建立一個index，調整其title的類型為string
PUT /my_index_new
{
"mappings": {
"my_type":{
"properties": {
"title":{
"type": "text"
}
}
}
}
}
（8）使用scroll api将資料批量查詢出來,
執行個體查詢一條即可：
GET /my_index/_search?scroll=1m
{
"query": {
"match_all": {}
},
"sort": ["_doc"],
"size": 1
}
回報資訊
{
"_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查出來的一批資料，批量寫入新索引
POST /_bulk
{ "index": { "_index": "my_index_new", "_type": "my_type", "_id": "2" }}
{ "title": "2017-01-02" }
回報資訊
{
"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）反複循環8~9，查詢一批又一批的資料出來，采取bulk api将每一批資料批量寫入新索引
（11）将goods_index alias切換到my_index_new上去，java應用會直接通過index别名使用新的索引中的資料，java應用程式不需要停機，零送出，高可用
POST /_aliases
{
"actions": [
{ "remove": { "index": "my_index", "alias": "goods_index" }},
{ "add": { "index": "my_index_new", "alias": "goods_index" }}
]
}
回報資訊
{
"acknowledged": true
}
（12）直接通過goods_index别名來查詢，是否ok
GET /goods_index/my_type/_search
{
"query": {
"match_all": {}
}
}
回報資訊：
{
"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"
}
}
]
}
}
檢視新的index 的 type類型
GET /goods_index/_mapping/my_type
{
"my_index_new": {
"mappings": {
"my_type": {
"properties": {
"title": {
"type": "text"
}
}
}
}
}
}
插入string類型的資料
PUT /goods_index/my_type/6
{
"title":"hello elasticsearch"
}
回報資訊
{
"_index": "my_index_new",
"_type": "my_type",
"_id": "6",
"_version": 1,
"result": "created",
"_shards": {
"total": 2,
"successful": 1,
"failed": 0
},
"created": true
}
查詢所有資訊
GET /goods_index/my_type/_search
{
"query": {
"match_all": {}
}
}
回報資訊
{
"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、總結
string 類型資料 可以 添加到新的index在中，并且原來的資訊已經導入（本次執行個體導入原來的一條資料）
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