Name relationship link between two different types in Apache Atlas - apache-atlas

Question

I am trying to name relationship link (by using attributeDefs) between two different types. The relationship is now registered in Atlas and definition fetch results as below:
{
"category": "RELATIONSHIP",
"guid": "9b1059c3-8707-46db-ae3c-e8d1b4ef6333",
"createdBy": "admin",
"updatedBy": "admin",
"createTime": 1625233869809,
"updateTime": 1625496519772,
"version": 6,
"name": "field_assignment",
"description": "someDescription.",
"typeVersion": "1.0",
"attributeDefs": [
{
"name": "LinkInformation",
"typeName": "string",
"isOptional": true,
"cardinality": "SINGLE",
"valuesMinCount": 0,
"valuesMaxCount": 1,
"isUnique": false,
"isIndexable": false,
"includeInNotification": false,
"searchWeight": -1
}
],
"relationshipCategory": "ASSOCIATION",
"propagateTags": "NONE",
"endDef1": {
"type": "custom_dataset",
"name": "fields",
"isContainer": false,
"cardinality": "SET",
"isLegacyAttribute": false
},
"endDef2": {
"type": "custom_field",
"name": "datasets",
"isContainer": false,
"cardinality": "SET",
"isLegacyAttribute": false
}
}
Now, I am trying to create a relationship between two types while defining an Entity for either type like
{
"entities": [
{
"typeName": "custom_field",
"createdBy": "admin",
"guid": -1000,
"attributes": {
"name": "type",
"datasets": [
{
"guid": "-200",
"typeName": "custom_dataset"
}
]
},
"classifications": [],
}
],
"referredEntities": {
"-200": {
"guid": "-200",
"typeName": "custome_dataset",
"relationshipAttributes" : {"LinkInformation": "key"},
"attributes": {
"qualifiedName": "test"
}
}
}
}
Through, while executing this, I don't see any error and entities are created but LinkInformation is null by simply doing a search by GUID for entities.
...
"relationshipAttributes": {
"typeName": "field_assignment",
"attributes": {
"LinkInformation": null
}
}
...
I am not able to find a good documentation anywhere for this. Can anyone help?

Answer 1

Atlas relationship between existing entities can be created either using entity GUIDs or uniqueAttributes in end1 and end2 which can be qualifiedName or any other unique attribute .
Please do note that top level typeName is the relationship def typeName while typeName inside end1 and end2 is entity typeName.
In case of relationship between hive_table and hive_db the relationship def typeName is: hive_table_db
So, if you want to create a relationship between hive_table and hive_db, the request would be:
POST: /api/atlas/v2/relationship
{
"typeName": "hive_table_db",
"end1": {
"typeName": "hive_table",
"uniqueAttributes": {
"qualifiedName": "db.table#cluster"
}
},
"end2": {
"typeName": "hive_db",
"uniqueAttributes": {
"qualifiedName": "db#cluster"
}
}
}
For predefined Atlas types you can find the relationship typeName from its definition inside relationshipAttributeDefs field
GET: /api/atlas/v2/types/typedef/name/hive_db
Which gives the following response:
{
"category": "ENTITY",
"guid": "9b1059c3-8707-46db-ae3c-e8d1b4ef6333",
"createdBy": "root",
"updatedBy": "root",
"createTime": 1548175553859,
"updateTime": 1548175822249,
"version": 2,
"name": "hive_db",
"description": "hive_db",
"typeVersion": "1.2",
"serviceType": "hive",
"attributeDefs": [
{
"name": "clusterName",
"typeName": "string",
"isOptional": false,
"cardinality": "SINGLE",
"valuesMinCount": 1,
"valuesMaxCount": 1,
"isUnique": false,
"isIndexable": true,
"includeInNotification": true,
"searchWeight": -1
},
{
"name": "location",
"typeName": "string",
"isOptional": true,
"cardinality": "SINGLE",
"valuesMinCount": 0,
"valuesMaxCount": 1,
"isUnique": false,
"isIndexable": false,
"includeInNotification": false,
"searchWeight": -1
},
{
"name": "parameters",
"typeName": "map<string,string>",
"isOptional": true,
"cardinality": "SINGLE",
"valuesMinCount": 0,
"valuesMaxCount": 1,
"isUnique": false,
"isIndexable": false,
"includeInNotification": false,
"searchWeight": -1
},
{
"name": "ownerType",
"typeName": "hive_principal_type",
"isOptional": true,
"cardinality": "SINGLE",
"valuesMinCount": 0,
"valuesMaxCount": 1,
"isUnique": false,
"isIndexable": false,
"includeInNotification": false,
"searchWeight": -1
}
],
"superTypes": [
"Asset"
],
"subTypes": [],
"relationshipAttributeDefs": [
{
"name": "tables",
"typeName": "array<hive_table>",
"isOptional": true,
"cardinality": "SET",
"valuesMinCount": -1,
"valuesMaxCount": -1,
"isUnique": false,
"isIndexable": false,
"includeInNotification": false,
"searchWeight": -1,
"constraints": [
{
"type": "ownedRef"
}
],
"relationshipTypeName": "hive_table_db",
"isLegacyAttribute": false
},
{
"name": "ddlQueries",
"typeName": "array<hive_db_ddl>",
"isOptional": true,
"cardinality": "SET",
"valuesMinCount": -1,
"valuesMaxCount": -1,
"isUnique": false,
"isIndexable": false,
"includeInNotification": false,
"searchWeight": -1,
"constraints": [
{
"type": "ownedRef"
}
],
"relationshipTypeName": "hive_db_ddl_queries",
"isLegacyAttribute": false
},
{
"name": "meanings",
"typeName": "array<AtlasGlossaryTerm>",
"isOptional": true,
"cardinality": "SET",
"valuesMinCount": -1,
"valuesMaxCount": -1,
"isUnique": false,
"isIndexable": false,
"includeInNotification": false,
"searchWeight": -1,
"relationshipTypeName": "AtlasGlossarySemanticAssignment",
"isLegacyAttribute": false
}
]
}
Further, you need to make sure the typeName in end1 and end2 is as per the relationship def, which you can check in type definition:
GET: /api/atlas/v2/types/typedef/name/hive_table_db
{
"category": "RELATIONSHIP",
"guid": "9b1059c3-8707-46db-ae3c-e8d1b4ef6333",
"createdBy": "root",
"updatedBy": "root",
"createTime": 1548175553894,
"updateTime": 1548175553894,
"version": 1,
"name": "hive_table_db",
"description": "hive_table_db",
"typeVersion": "1.0",
"serviceType": "hive",
"attributeDefs": [],
"relationshipCategory": "COMPOSITION",
"propagateTags": "NONE",
"endDef1": {
"type": "hive_table",
"name": "db",
"isContainer": false,
"cardinality": "SINGLE",
"isLegacyAttribute": true
},
"endDef2": {
"type": "hive_db",
"name": "tables",
"isContainer": true,
"cardinality": "SET",
"isLegacyAttribute": false
}
}