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https://issues.apache.org/jira/browse/DRILL-7359?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16950407#comment-16950407
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ASF GitHub Bot commented on DRILL-7359:
---------------------------------------
paul-rogers commented on issue #1870: DRILL-7359: Add support for DICT type in
RowSet Framework
URL: https://github.com/apache/drill/pull/1870#issuecomment-541440586
Let's continue to assume that `DICT` is, essentially, `DICT<KEY_TYPE,
VALUE_TYPE>` and that we can think of the `DICT`, when writing, as a pair of
arrays: one for keys, one for values. (Because vectors are write-once, we have
to add (key, value) pairs one by one. If so, then we need a new form of writer,
a `DictWriter` that has semantics such as:
```
ObjectWriter key();
ObjectWriter value();
void save();
```
The `key()` gives us an object writer that lets us access the key writer. If
we restrict keys to be scalars, then we can just do:
```
ScalarWriter key();
```
Values can, I imagine, be of any type. So, the `ObjectWriter` lets us work
with them generically. Suppose we had a `DICT<VARCHAR,DOUBLE>`, we could do:
```
DictWriter dictWriter = rowWriter.dict("myDict");
dictWriter.key().setString("fred");
dictWriter.value().scalar().setDouble(123.45)
dictWriter.save();
dictWriter.key().setString("barney");
dictWriter.value().scalar().setDouble(98.76)
dictWriter.save();
```
This means that, in the `ObjectWriter()`, we need to add a new method,
`dict()`, which will return a `DictWriter`, and we need to define the
`DictWriter` interface.
There is quite a bit of commentary in the column accessor package that
(tries) to explain the structure behind these writers. Perhaps that might help
explain the ideas here.
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> Add support for DICT type in RowSet Framework
> ---------------------------------------------
>
> Key: DRILL-7359
> URL: https://issues.apache.org/jira/browse/DRILL-7359
> Project: Apache Drill
> Issue Type: New Feature
> Reporter: Bohdan Kazydub
> Assignee: Bohdan Kazydub
> Priority: Major
> Fix For: 1.17.0
>
>
> Add support for new DICT data type (see DRILL-7096) in RowSet Framework
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