ES Parent-Child document query

Features of parent-child documents

1. The parent/subdocument is completely independent.

2. Parent document updates do not affect sub-documents.

3. Sub-document updates do not affect parent documents or other subdocuments.

Mapping and indexing of parent-child documents

1. The establishment of a parent-child relationship type must be determined when the index is new or update-mapping

PUT/company{"Mappings": {    "Branch": {},//Parent Document Type    "Employee": {                  "_parent": {        "type":"Branch"      //Child Document Type      }    }  }}

2. The index of the parent document is the same as the normal document index.

post/company/branch/_bulk{"Index": {"_id":"London" }}{ "name":"London Westminster"," City":"London","Country":"UK" }

3. The subdocument index must specify its corresponding parent document ID, acting as:

• Establish associations between parent-child documents
• Ensure that the subdocument can be indexed to the Shard where the parent document resides (parent ID as Route)

put/company/employee/1? parent=london//Specify ID = parent document for London{  "name":"Alice Smith",  "DOB":"1970-10-24",  "Hobby":"Hiking"}

4. If you want to change the document's parent document, you cannot just update or reindex the old document (the new parent document may be on a different shard), you need to delete the old document and then re-index it.

Application of parent-child relationship

Seeing Parent-child relationships, it's easy to think of a variety of JOIN operations like SQL-such as querying a document and retrieving all of the parent or child documents.

However, similar JOIN queries are not supported in ES.

The parent-child relationship in ES is basically understood to be just a filter condition, as follows:

//query a document, only the document has a "parent document" and meets certain criteria to match{"has_parent": {//whether the document has a parent      "type":"Branch",//its parent must be of type branch      "Query": {//its parent must meet the following query criteria        "Match": {          "Country":"UK"        }      }    }                           //if the above conditions are met, hit the document}//query a document, only the document has a "subdocument" and meet certain criteria to calculate the match{"Has_child": {//whether the document has a child      "type":"Employee",//the child's type must be an employee      "Query": {//its parent must meet the following query criteria        "Match": {          "name":"Alice Smith"        }      }    }                                //if the above conditions are met, hit the document}

1. Has_child: Find the parent document based on the content of the subdocument

//Requestget/company/branch/_search{"Query": {    "Has_child": {//Query the parent document that satisfies the criteria based on the child's content      "type":"Employee",      "Query": {//to perform a match query operation in child        "Match": {          "name":"Alice Smith"        }      }    }  }}//Results{  "took":2,  "timed_out":false,  "_shards": {    " Total":5,    "successful":5,    "failed":0  },  "hits": {    " Total":1,    "Max_score":1,    "hits": [      {        "_index":" Company",        "_type":"Branch",//Attention!!! Returns the parent's document        "_id":"London",        "_score":1,        "_source": {          "name":"London Westminster",          " City":"London",          "Country":"UK"        }      }    ]  }}

2. Has_parent: Find sub-documents based on the contents of the parent document

//Request Get/company/employee/_search{  "Query": {    "has_parent": {//Query the child document that satisfies the criteria, based on the contents of the parent      "type":"Branch",       "Query": {//to execute a match query query in the parent        "Match": {          "Country":"UK"        }      }    }  }}//Results{  "took":2,  "timed_out":false,  "_shards": {    " Total":5,    "successful":5,    "failed":0  },  "hits": {    " Total":1,    "Max_score":1,    "hits": [      {        "_index":" Company",        "_type":"Employee",//Attention!!! The child's document is returned        "_id":"1",        "_score":1,        "_routing":"London",        "_parent":"London",        "_source": {          "name":"Alice Smith",          "DOB":"1970-10-24",          "Hobby":"Hiking"        }      }    ]  }}

3. Children Aggregation:

ES Parent-Child document query