Vincenz Priesnitz created AVRO-1347:
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Summary: Improve name and alias matching for named schemas
Key: AVRO-1347
URL: https://issues.apache.org/jira/browse/AVRO-1347
Project: Avro
Issue Type: Improvement
Components: java
Reporter: Vincenz Priesnitz
When reading an avro file with a named schema, the aliases of the writers
schema are not taken into account; only the aliases of the readers are matched
against the writers name. Even if the writers aliases match the readers name,
the schemas will not be matched.
For example, the following two enum schemas will not be matched, even though
they share a common alias.
{code}
{
"type" : "enum",
"name" : "foo",
"alias" : "CommonAlias",
"symbols" : ["LEFT", "RIGHT"]
}
{code}
{code}
{
"type" : "enum",
"name" : "bar",
"alias" : "CommonAlias",
"symbols" : ["LEFT", "RIGHT"]
}
{code}
In most cases, the DatumReader resolves records of different names or
namespaces by matching their fields.
Unfortunately, there are some cases, where this sort of matching is not
happening, but just the names are compared:
* Other named nodes, like enums, fixed or fieldschemas are not matched this
way.
* A record inside a union is also only matched by the full name.
The latter one is especially tricky, since two recordschemas that match
structurally but differ in name or space, are interexchangable until they are
put into an union, at which point an exception is thrown.
I propose that two named schemas are matched, when they share a common name or
alias.
I implemented said changes and added a java annotation @AvroAlias(alias, space)
that allows one to add an alias to a record, enum or field.
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