How to define a default value when creating an index in Elasticsearch - python-3.x

Question

I need to create an index in elasticsearch by assigning a default value for a field. Ex,
In python3,
request_body = {
"settings":{
"number_of_shards":1,
"number_of_replicas":1
},
"mappings":{
"properties":{
"name":{
"type":"keyword"
},
"school":{
"type":"keyword"
},
"pass":{
"type":"keyword"
}
}
}
}
from elasticsearch import Elasticsearch
es = Elasticsearch(['https://....'])
es.indices.create(index="test-index", ignore=400, body= request_body)
in above scenario, the index will be created with those fields. But i need to put a default value to "pass" as True. Can i do that here?

Answer 1

Elastic search is schema-less. It allows any number of fields and any content in fields without any logical constraints.
In a distributed system integrity checking can be expensive so checks like RDBMS are not available in elastic search.
Best way is to do validations at client side.
Another approach is to use ingest
Ingest pipelines let you perform common transformations on your data before indexing. For example, you can use pipelines to remove fields, extract values from text, and enrich your data.
**For testing**
POST _ingest/pipeline/_simulate
{
"pipeline": {
"processors": [
{
"script": {
"lang": "painless",
"source": "if (ctx.pass ===null) { ctx.pass='true' }"
}
}
]
},
"docs": [
{
"_index": "index",
"_type": "type",
"_id": "2",
"_source": {
"name": "a",
"school":"aa"
}
}
]
}
PUT _ingest/pipeline/default-value_pipeline
{
"description": "Set default value",
"processors": [
{
"script": {
"lang": "painless",
"source": "if (ctx.pass ===null) { ctx.pass='true' }"
}
}
]
}
**Indexing document**
POST my-index-000001/_doc?pipeline=default-value_pipeline
{
"name":"sss",
"school":"sss"
}
**Result**
{
"_index" : "my-index-000001",
"_type" : "_doc",
"_id" : "hlQDGXoB5tcHqHDtaEQb",
"_score" : 1.0,
"_source" : {
"school" : "sss",
"pass" : "true",
"name" : "sss"
}
},