如何解决根据 Elastic Search 中过滤器的最后一个条目分组
包含商店购买商品的索引,其中每个商品都有一个 order_id。 而且我只需要按每个订单的最后项的颜色分组。
数据结构:
{
"order_id": 1,"product_id":235233
"color": "Blue","purchase_date": "2020-08-21T05:53:43.362Z"
},{
"order_id": 1,"product_id":2352662
"color": "Black","purchase_date": "2020-08-23T05:53:43.362Z"
},{
"order_id": 2,"product_id":855477
"color": "Blue","purchase_date": "2020-08-22T05:53:43.362Z"
},"product_id":322352
"color": "Red","purchase_date": "2020-08-24T05:53:43.362Z"
},{
"order_id": 3,"product_id":3225235
"color": "Red","purchase_date": "2020-08-25T05:53:43.362Z"
}
预期结果
黑色:1(order_id 1 的最后一个产品的颜色)
Red:2(order_id 2,3 的最后一个产品的颜色)
基于 this answer,我可以将每个订单的最后一个项目作为整个项目,但我正在寻找的是直接获取每种颜色的项目数
POST /items/_search?search_type=count
{
"aggs": {
"group": {
"terms": {
"field": "order_id"
},"aggs": {
"group_items": {
"top_hits": {
"size": 1,"sort": [
{
"purchase_date": {
"order": "desc"
}
}
]
}
}
}
}
}
}
下面给出了所有订单商品的每种颜色的商品数量,而不仅仅是每个订单的最后一个。
GET /items/_search?search_type=count
{
"size":0,"aggs": {
"colors": {
"terms": {
"field": "color.keyword"
}
}
}
}
解决方法
解决该问题的另一种方法是创建并维护一个单独的索引 (latest_by_order
),用于跟踪每个订单的最新文档。
这可以使用转换 (see docs) 来实现。
可以使用以下命令创建此类转换:
PUT _transform/latest_by_order
{
"source": {
"index": "items"
},"dest": {
"index": "latest_by_order"
},"latest": {
"unique_key": ["order_id"],"sort": "purchase_date"
}
}
然后,可以在新的(转换后的)索引之上进行二次分析。 以下请求:
GET latest_by_order/_search
{
"size": 0,"aggs": {
"count_by_color": {
"terms": {
"field": "color.keyword"
}
}
}
}
将产生以下响应:
{
"took" : 2,"timed_out" : false,"_shards" : {
"total" : 1,"successful" : 1,"skipped" : 0,"failed" : 0
},"hits" : {
"total" : {
"value" : 3,"relation" : "eq"
},"max_score" : null,"hits" : [ ]
},"aggregations" : {
"count_by_color" : {
"doc_count_error_upper_bound" : 0,"sum_other_doc_count" : 0,"buckets" : [
{
"key" : "Red","doc_count" : 2
},{
"key" : "Black","doc_count" : 1
}
]
}
}
}
,
您可以使用 group by color
并按 purchase_date
的最大值排序,如下所示:
{
"size": 0,"aggs": {
"group": {
"terms": {
"field": "color.keyword","order": {
"by_latest_purchase": "desc"
}
},"aggs": {
"by_latest_purchase": {
"max": {
"field": "purchase_date"
}
}
}
}
}
}
但您最终仍会得到 blue
b/c,这是您的文档中存在的一种颜色,我不知道是否可以将其过滤掉。
当有疑问(或其他所有方法都失败)时,scripted metric aggregations 来救援:
{
"size": 0,"aggs": {
"by_color": {
"scripted_metric": {
"init_script": "state.by_order_id = [:]","map_script": """
def color = doc['color.keyword'].value;
def date = doc['purchase_date'].value.millis;
def order_id = doc['order_id'].value;
def current_group = ['color':color,'date': date];
if (state.by_order_id.containsKey(order_id)) {
def max_group = state.by_order_id[order_id];
if (date > max_group.date) {
// we've found a new maximum
state.by_order_id[order_id] = current_group
}
} else {
state.by_order_id[order_id] = current_group;
}
""","combine_script": """
def colors_vs_count = [:];
for (def group : state.by_order_id.entrySet()) {
def order_id = group.getKey();
def color = group.getValue()['color'];
if (colors_vs_count.containsKey(color)) {
colors_vs_count[color]++;
} else {
colors_vs_count[color] = 1;
}
}
return colors_vs_count;
""","reduce_script": "return states"
}
}
}
}
产量:
...
"aggregations" : {
"by_color" : {
"value" : [
{
"Red" : 2,"Black" : 1
}
]
}
}
这是一个 JSON 友好的精简版脚本:
{"size":0,"aggs":{"by_color":{"scripted_metric":{"init_script":"state.by_order_id = [:]","map_script":" def color = doc['color.keyword'].value;\n def date = doc['purchase_date'].value.millis;\n def order_id = doc['order_id'].value;\n \n def current_group = ['color':color,'date': date];\n \n if (state.by_order_id.containsKey(order_id)) {\n def max_group = state.by_order_id[order_id];\n if (date > max_group.date) {\n state.by_order_id[order_id] = current_group\n }\n } else {\n state.by_order_id[order_id] = current_group;\n }","combine_script":" def colors_vs_count = [:];\n \n for (def group : state.by_order_id.entrySet()) {\n def order_id = group.getKey();\n def color = group.getValue()['color'];\n if (colors_vs_count.containsKey(color)) {\n colors_vs_count[color]++;\n } else {\n colors_vs_count[color] = 1;\n }\n }\n \n return colors_vs_count;","reduce_script":"return states"}}}}
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