SchemaEnv cached twice when using `addSchema`

[0bex0]

What version of Ajv are you using? Does the issue happen if you use the latest version?
8.17.1

Ajv options object

const ajv = new Ajv()

JSON Schema

{
    "$id": "http://example.com/example.json",
    "type": "object",
    "definitions": {},
    "$schema": "http://json-schema.org/draft-07/schema#",
    "properties": {
        "exampleProperty": {
            "$id": "/properties/exampleProperty",
            "type": "string",
            "title": "An example property",
            "default": "This is an example property",
        },
    },
}

Your code

ajv.addSchema(someSchema, 'exampleSchema')

Caching

Output from logging ajv internal cache keys (stored in ajv._cache):

{"$schema":"http://json-schema.org/draft-07/schema#","$id":"http://json-schema.org/draft-07/schema#","title":"Core schema meta-schema","definitions":{"schemaArray":{"type":"array","minItems":1,"items":{"$ref":"#"}},"nonNegativeInteger": {"type":"integer","minimum":0},"nonNegativeIntegerDefault0":{"allOf":[{"$ref":"#/definitions/nonNegativeInteger"},{"default":0}]},"simpleTypes":{"enum":["array","boolean","integer","null","number","object","string"]},"stringArray":{"type":"array","items":{"type":"string"},"uniqueItems":true,"default":[]}},"type":["object","boolean"],"properties":{"$id":{"type":"string","format":"uri-reference"},"$schema":{"type":"string","format":"uri"},"$ref":{"type":"string","format":"uri-reference"},"$comment":{"type":"string"},"title":{"type":"string"},"description":{"type":"string"},"default":true,"readOnly":{"type":"boolean","default":false},"examples":{"type":"array","items":true},"multipleOf":{"type":"number","exclusiveMinimum":0},"maximum":{"type":"number"},"exclusiveMaximum":{"type":"number"},"minimum":{"type":"number"},"exclusiveMinimum":{"type":"number"},"maxLength":{"$ref":"#/definitions/nonNegativeInteger"},"minLength":{"$ref":"#/definitions/nonNegativeIntegerDefault0"},"pattern":{"type":"string","format":"regex"},"additionalItems":{"$ref":"#"},"items":{"anyOf":[{"$ref":"#"},{"$ref":"#/definitions/schemaArray"}],"default":true},"maxItems":{"$ref":"#/definitions/nonNegativeInteger"},"minItems":{"$ref":"#/definitions/nonNegativeIntegerDefault0"},"uniqueItems":{"type":"boolean","default":false},"contains":{"$ref":"#"},"maxProperties":{"$ref":"#/definitions/nonNegativeInteger"},"minProperties":{"$ref":"#/definitions/nonNegativeIntegerDefault0"},"required":{"$ref":"#/definitions/stringArray"},"additionalProperties":{"$ref":"#"},"definitions":{"type":"object","additionalProperties":{"$ref":"#"},"default":{}},"properties":{"type":"object","additionalProperties":{"$ref":"#"},"default":{}},"patternProperties":{"type":"object","additionalProperties":{"$ref":"#"},"propertyNames":{"format":"regex"},"default":{}},"dependencies":{"type":"object","additionalProperties":{"anyOf":[{"$ref":"#"},{"$ref":"#/definitions/stringArray"}]}},"propertyNames":{"$ref":"#"},"const":true,"enum":{"type":"array","items":true,"minItems":1,"uniqueItems":true},"type":{"anyOf":[{"$ref":"#/definitions/simpleTypes"},{"type":"array","items":{"$ref":"#/definitions/simpleTypes"},"minItems":1,"uniqueItems":true}]},"format":{"type":"string"},"contentMediaType":{"type":"string"},"contentEncoding":{"type":"string"},"if":{"$ref":"#"},"then":{"$ref":"#"},"else":{"$ref":"#"},"allOf":{"$ref":"#/definitions/schemaArray"},"anyOf":{"$ref":"#/definitions/schemaArray"},"oneOf":{"$ref":"#/definitions/schemaArray"},"not":{"$ref":"#"}},"default":true}
{"$id":"http://example.com/example.json","type":"object","properties":{"exampleProperty":{"$id":"/properties/exampleProperty","type":"string","title":"An example property","default":"This is an example property"}}}

Output from console.log(ajv.schemas):

{
  'http://json-schema.org/draft-07/schema': <ref *1> SchemaEnv {
    refs: {
      'http://json-schema.org/draft-07/schema#/definitions/nonNegativeInteger': [Object],
      'http://json-schema.org/draft-07/schema#/definitions/nonNegativeIntegerDefault0': [SchemaEnv],
      'http://json-schema.org/draft-07/schema#/definitions/schemaArray': [SchemaEnv],
      'http://json-schema.org/draft-07/schema#/definitions/stringArray': [Object],
      'http://json-schema.org/draft-07/schema#/definitions/simpleTypes': [Object]
    },
    dynamicAnchors: {},
    schema: {
      '$schema': 'http://json-schema.org/draft-07/schema#',
      '$id': 'http://json-schema.org/draft-07/schema#',
      title: 'Core schema meta-schema',
      definitions: [Object],
      type: [Array],
      properties: [Object],
      default: true
    },
    schemaId: '$id',
    root: [Circular *1],
    baseId: 'http://json-schema.org/draft-07/schema',
    schemaPath: undefined,
    localRefs: {},
    meta: true,
    '$async': undefined,
    validateName: ValueScopeName {
      str: 'validate0',
      prefix: 'validate',
      value: [Object],
      scopePath: [_Code]
    },
    validate: [Function: validate0] {
      errors: null,
      schema: [Object],
      schemaEnv: [Circular *1]
    }
  },
  exampleSchema: <ref *2> SchemaEnv {
    refs: {},
    dynamicAnchors: {},
    schema: {
      '$id': 'http://example.com/example.json',
      type: 'object',
      properties: [Object]
    },
    schemaId: '$id',
    root: [Circular *2],
    baseId: 'http://example.com/example.json',
    schemaPath: undefined,
    localRefs: {},
    meta: undefined,
    '$async': undefined
  }
}

What results did you expect?
I would expect the SchemaEnv object to only be cached in one place, when adding a schema through addSchema function the schema is cached twice:

• Within this._cache in _addSchema call here.
• Within this.schemas in addSchema call here.

For extremely large schemas the entry in this._cache is particularly memory intensive since it stores the SchemaEnv object using the entire schema as a key. It would be preferable to be able to use addSchema to cache the SchemaEnv object only once using the key provided in the addSchema call to optimise the memory used by caching.

Are you going to resolve the issue?
Yes