parquet-cli reports nested columns as null
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描述
### Describe the bug, including details regarding any error messages, version, and platform.
Using Parquet CLI 1.15.0 via Mac Homebrew, I noticed some surprising behaviour with the `parquet-cli` and nested columns.
`parquet schema catalog.parquet` returns a schema showing the nested types (I've trimmed the field list slightly):
```avro
{
"type" : "record",
"name" : "schema",
"fields" : [ {
"name" : "item_id",
"type" : "string"
}, {
"name" : "title",
"type" : [ "null", "string" ],
"default" : null
}, {
"name" : "language",
"type" : [ "null", "string" ],
"default" : null
}, {
"name" : "subjects",
"type" : [ "null", {
"type" : "array",
"items" : {
"type" : "record",
"name" : "list",
"fields" : [ {
"name" : "element",
"type" : "string"
} ]
}
} ],
"default" : null
}, {
"name" : "authors",
"type" : [ "null", {
"type" : "array",
"items" : {
"type" : "record",
"name" : "list",
"namespace" : "list2",
"fields" : [ {
"name" : "element",
"type" : "string"
} ]
}
} ],
"default" : null
} ]
}
```
`parquet dictionary -c subjects.list.element catalog.parquet` will return the expected values for those fields as well:
```
Row group 0 dictionary for "subjects.list.element":
0: "Bestsellers"
1: "Biography"
2: "Fantasy Fiction"
3: "Music Theory"
4: "Disability"
5: "Family"
6: "Young Adult"
```
However, when using `cat` or `head` to display the file contents those fields are displayed as null:
```
{"bmc_id": "id1", "title": null, "language": "en", "subjects": null, "authors": null}
{"bmc_id": "id2", "title": null, "language": "en", "subjects": null, "authors": null,}
{"bmc_id": "id3", "title": null, "language": "en", "subjects": null, "authors": null}
```
Other tools like PyArrow or Pandas do display those values as arrays. I created this as a bug because it _looks_ like it's working and if those fields are nullable, there's no way to tell whether the null value is correct.
### Component(s)
_No response_
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调研方向
使用 `parquet schema`、`parquet dictionary -c subjects.list.element` 以及对 `catalog.parquet` 执行的 `cat` 或 `head`,复现 Parquet CLI 1.15.0 中的问题。将 dictionary 命令报告的嵌套列值与显示的记录进行比较,并检查处理这些命令的 parquet-cli 路径。完成标准是 `cat` 和 `head` 显示嵌套数组,而不是错误地将其显示为 null。
由索引模型根据 Issue 内容生成。
评估
- 技术栈
- java
- 领域
- cli, data
- Issue 类型
- 缺陷
- 难度
- 3/5
- 预计耗时
- 1-2 天
- 活跃度
- 停滞
- 描述清晰度
- 需要澄清
- 新手友好度
- 35/100