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https://issues.apache.org/jira/browse/DRILL-7509?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17015448#comment-17015448
]
ASF GitHub Bot commented on DRILL-7509:
---------------------------------------
paul-rogers commented on pull request #1954: DRILL-7509: Incorrect TupleSchema
is created for DICT column when querying Parquet files
URL: https://github.com/apache/drill/pull/1954#discussion_r366598557
##########
File path:
exec/vector/src/main/java/org/apache/drill/exec/record/metadata/MetadataUtils.java
##########
@@ -187,6 +187,10 @@ public static ColumnMetadata newMapArray(String name,
TupleMetadata schema) {
return new MapColumnMetadata(name, DataMode.REPEATED, (TupleSchema)
schema);
}
+ public static DictColumnMetadata newDictArray(String name, TupleMetadata
schema) {
+ return new DictColumnMetadata(name, DataMode.REPEATED, (TupleSchema)
schema);
Review comment:
Picking up on a comment in your PR description, I wonder if we have the
wrong semantics here. It is true that DICT is *implemented* as a map. But, at
the metadata (descriptive) level, it is not a map, and is not constructed from
a map; it is instead a `<KEY,VALUE>` pair.
I'm not sure we're doing ourselves a favor by exposing the implementation
detail (a kind of map) in our metadata description.
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> Incorrect TupleSchema is created for DICT column when querying Parquet files
> ----------------------------------------------------------------------------
>
> Key: DRILL-7509
> URL: https://issues.apache.org/jira/browse/DRILL-7509
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.16.0
> Reporter: Bohdan Kazydub
> Assignee: Bohdan Kazydub
> Priority: Major
> Fix For: 1.18.0
>
>
> When {{DICT}} column is queried from Parquet file, its {{TupleSchema}}
> contains nested element, e.g. `map`, itself contains `key` and `value`
> fields, rather than containing the `key` and `value` fields in the {{DICT}}'s
> {{TupleSchema}} itself. The nested element, `map`, comes from the inner
> structure of Parquet's {{MAP}} (which corresponds to Drill's {{DICT}})
> representation.
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