druid-docs-cn/development/extensions-core/orc.md

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---
id: orc
title: "ORC Extension"
---
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## ORC extension
This Apache Druid extension enables Druid to ingest and understand the Apache ORC data format.
The extension provides the [ORC input format](../../ingestion/data-formats.md#orc) and the [ORC Hadoop parser](../../ingestion/data-formats.md#orc-hadoop-parser)
for [native batch ingestion](../../ingestion/native-batch.md) and [Hadoop batch ingestion](../../ingestion/hadoop.md), respectively.
Please see corresponding docs for details.
To use this extension, make sure to [include](../../development/extensions.md#loading-extensions) `druid-orc-extensions`.
### Migration from 'contrib' extension
This extension, first available in version 0.15.0, replaces the previous 'contrib' extension which was available until
0.14.0-incubating. While this extension can index any data the 'contrib' extension could, the JSON spec for the
ingestion task is *incompatible*, and will need modified to work with the newer 'core' extension.
To migrate to 0.15.0+:
* In `inputSpec` of `ioConfig`, `inputFormat` must be changed from `"org.apache.hadoop.hive.ql.io.orc.OrcNewInputFormat"` to
`"org.apache.orc.mapreduce.OrcInputFormat"`
* The 'contrib' extension supported a `typeString` property, which provided the schema of the
ORC file, of which was essentially required to have the types correct, but notably _not_ the column names, which
facilitated column renaming. In the 'core' extension, column renaming can be achieved with
[`flattenSpec`](../../ingestion/index.md#flattenspec). For example, `"typeString":"struct<time:string,name:string>"`
with the actual schema `struct<_col0:string,_col1:string>`, to preserve Druid schema would need replaced with:
```json
"flattenSpec": {
"fields": [
{
"type": "path",
"name": "time",
"expr": "$._col0"
},
{
"type": "path",
"name": "name",
"expr": "$._col1"
}
]
...
}
```
* The 'contrib' extension supported a `mapFieldNameFormat` property, which provided a way to specify a dimension to
flatten `OrcMap` columns with primitive types. This functionality has also been replaced with
[`flattenSpec`](../../ingestion/index.md#flattenspec). For example: `"mapFieldNameFormat": "<PARENT>_<CHILD>"`
for a dimension `nestedData_dim1`, to preserve Druid schema could be replaced with
```json
"flattenSpec": {
"fields": [
{
"type": "path",
"name": "nestedData_dim1",
"expr": "$.nestedData.dim1"
}
]
...
}
```