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https://issues.apache.org/jira/browse/DRILL-8450?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17752099#comment-17752099
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ASF GitHub Bot commented on DRILL-8450:
---------------------------------------
cgivre commented on code in PR #2819:
URL: https://github.com/apache/drill/pull/2819#discussion_r1287295957
##########
common/src/main/java/org/apache/drill/common/Typifier.java:
##########
@@ -88,6 +96,40 @@ public class Typifier {
// If a String contains any of these, try to evaluate it as an equation
private static final char[] MathCharacters = new char[]{'+', '-', '/', '*',
'='};
+ /**
+ * This function infers the Drill data type of unknown data.
+ * @param data The input text of unknown data type.
+ * @return A {@link MinorType} of the Drill data type.
+ */
+ public static MinorType typifyToDrill (String data) {
+ Entry<Class, String> result = Typifier.typify(data);
+ String dataType = result.getKey().getSimpleName();
+
+ // If the string is empty, return UNKNOWN
Review Comment:
@mbeckerle Drill doesn't really have an `UNKNOWN` data type. The way the
typifier works is that if it can't determine the datatype, it falls back to
string which can basically accept anything.
Regarding the lists... The issue is that to create a list, you have to set
the data mode to `REPEATED`. The problem with XML is that there's no real way
to know if a field is repeated or not. Consider this:
```xml
<book>
<author>a</author>
</book>
<book>
<author>a1</author>
<author>a2</author>
</book>
```
Since Drill uses the streaming reader, when it first encounters the `author`
field, it would add an entry for a VARCHAR field. However, when it gets to the
next author record, it should be list, but there's no way to really know that
w/o a schema.
With JSON we don't have this problem because it uses `[` to denote lists.
Does that make sense?
> Add Data Type Inference to XML Format Plugin
> --------------------------------------------
>
> Key: DRILL-8450
> URL: https://issues.apache.org/jira/browse/DRILL-8450
> Project: Apache Drill
> Issue Type: Improvement
> Components: Format - XML
> Affects Versions: 1.21.1
> Reporter: Charles Givre
> Assignee: Charles Givre
> Priority: Major
> Fix For: 1.22.0
>
>
> This PR adds data type inference to the XML format plugin. In similar
> fashion to other plugins, it adds a new configuration parameter: allTextMode,
> which when set to true, reads all data as strings. The default is true.
> Note that the inference is limited to doubles, date, timestamps, boolean and
> strings.
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