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https://issues.apache.org/jira/browse/AVRO-600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12891325#action_12891325
]
Doug Cutting commented on AVRO-600:
-----------------------------------
An example:
Data written with:
{code}
{"type": "record", "name": "org.x.Foo", "fields": [
{"name": "a", "type": "int"},
{"name": "b", "type": "int"}
]
}
{code}
Could be read with:
{code}
{"type": "record", "name": "org.y.Bar", "fields": [
{"name": "c", "type": "int", "aliases": ["a"]},
{"name": "d", "type": "int", "default": 0}
],
"aliases": ["org.x.Foo"]
}
{code}
It would be an error for a type alias to name an already-defined type or for a
field alias to name an already-defined field.
The semantics would be equivalent to rewriting the writer's schema, replacing
matching aliased types and fields with their names in the reader's schema. In
the above example, the writer's schema would be rewritten as:
{code}
{"type": "record", "name": "org.y.Bar", "fields": [
{"name": "c", "type": "int"},
{"name": "b", "type": "int"}
]
}
{code}
When instances are read, values for "a" would be read into the "c" field,
values for "b" would be dropped, and "d" would have the default value of zero.
> add support for type and field name aliases
> -------------------------------------------
>
> Key: AVRO-600
> URL: https://issues.apache.org/jira/browse/AVRO-600
> Project: Avro
> Issue Type: New Feature
> Components: java, spec
> Reporter: Doug Cutting
>
> It would be good if Avro would permit one to still read data if a type or
> field name has been changed. I propose we add a notion of name _aliases_.
> Aliases could be listed for every named type and for record fields. The
> writers schema would be permitted to contain any of the aliases.
> In general, this permits one to construct schemas that can read different
> types into a single type. One could use this not just to handle renamings,
> but also to join different datasets. For example, if two datasets each
> contain differently named records with a date and an ip address field, this
> could be used be used to project these both to a single record with just
> those fields.
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