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https://issues.apache.org/jira/browse/PARQUET-2292?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17719365#comment-17719365
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ASF GitHub Bot commented on PARQUET-2292:
-----------------------------------------
gszadovszky commented on code in PR #1078:
URL: https://github.com/apache/parquet-mr/pull/1078#discussion_r1185124781
##########
parquet-avro/src/main/java/org/apache/parquet/avro/AvroRecordConverter.java:
##########
@@ -169,6 +172,46 @@ public void add(Object value) {
}
}
+ /**
+ * Returns the specific data model for a given SpecificRecord schema by
reflecting the underlying
+ * Avro class's `MODEL$` field, or Null if the class is not on the classpath
or reflection fails.
+ */
+ static SpecificData getModelForSchema(Schema schema) {
+ final Class<?> clazz;
+
+ if (schema != null && (schema.getType() == Schema.Type.RECORD ||
schema.getType() == Schema.Type.UNION)) {
+ clazz = SpecificData.get().getClass(schema);
+ } else {
+ return null;
+ }
+
+ final SpecificData model;
+ try {
+ final Field modelField = clazz.getDeclaredField("MODEL$");
+ modelField.setAccessible(true);
+
+ model = (SpecificData) modelField.get(null);
+ } catch (Exception e) {
+ return null;
+ }
+
+ try {
+ final String avroVersion =
Schema.Parser.class.getPackage().getImplementationVersion();
+ // Avro 1.8 doesn't include conversions in the MODEL$ field
+ if (avroVersion.startsWith("1.8.")) {
Review Comment:
> so I've tested 1.7 and 1.8; since 1.9 Avro has stably used the `MODEL$`
field to hold all conversions, so I feel reasonably confident about relying on
this. If that changes, we'll catch it in the new unit tests +1
This sounds perfect to me. Thanks a lot for the additional work!
> If you want, I can surround invocations of `getModelForSchema` in a
try/catch (in `AvroReadSupport`/`AvroWriteSupport`), and just use the default
SpecificDataSupplier if they throw anything. That way any unexpected behavior
would just result in logical types not being used.
Yes, I think this fallback mechanism sounds reasonable to me.
> Improve default SpecificRecord model selection for Avro{Write,Read}Support
> --------------------------------------------------------------------------
>
> Key: PARQUET-2292
> URL: https://issues.apache.org/jira/browse/PARQUET-2292
> Project: Parquet
> Issue Type: Improvement
> Reporter: Claire McGinty
> Assignee: Claire McGinty
> Priority: Major
>
> AvroWriteSupport/AvroReadSupport can improve the precision of their default
> `model` selection. Currently they default to new
> SpecificDataSupplier().get()[0]. This means that SpecificRecord classes that
> contain logical types will fail out-of-the-box unless a specific
> DATA_SUPPLIER is configured that contains logical type conversions.
> I think we can improve this and make logical types work by default by
> defaulting to the value of the `MODEL$` field that every SpecificRecordBase
> implementation contains, which already contains all the logical conversions
> for that Avro type. It would require reflection, but that's what the Avro
> library is already doing to fetch models for Specific types[1].
>
> [0]
> [https://github.com/apache/parquet-mr/blob/d38044f5395494e1543581a4b763f624305d3022/parquet-avro/src/main/java/org/apache/parquet/avro/AvroWriteSupport.java#L403-L407]
> [1]
> https://github.com/apache/avro/blob/release-1.11.1/lang/java/avro/src/main/java/org/apache/avro/specific/SpecificData.java#L76-L86
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