alpreu opened a new issue, #16959:
URL: https://github.com/apache/pulsar/issues/16959
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## Motivation
Currently, the `Schema` interface in the public client-api does not provide
access to a sensible hash function. The fallback to Java’s object-equality
makes it unfit for use in most hash-based collections. For example, it prevents
usage as a key in a cache.
Further, the lack of a reliable equals function means that there is no way
to identify if two schemas are the same thing.
## Goal
The goal of this proposal is to provide a sensible `hashCode` and `equals`
implementation for Schema as part of the public API.
Currently, pulsar-common contains `SchemaHash`, a wrapper class that exists
to solve the aforementioned problems. However, `SchemaHash` is not part of the
public API, so users should not depend on it.
## API Changes
There is no further change required as moving `SchemaHash` from
pulsar-common to the public API. The only further change could be to re-think
the class name, as the wrapper offers more than just a schemas hash.
## Implementation
Move `SchemaHash` from pulsar-common
`org.apache.pulsar.common.protocol.schema` package into pulsar-client-api
`org.apache.pulsar.common.schema` package.
## Reject Alternatives
Providing default methods for `equals` and `hashCode` directly on the
`Schema` interface is not possible because Java prohibits overriding the base
Object methods.
Another option would be to provide the `hashCode` and `equals` functionality
through similarly-named default methods that could be used by any `Schema`
implementation. The drawback of this idea is that it requires developers to
override the equals and hashCode to use these provided methods, as well as
possibly polluting the interface.
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