cloud-fan commented on a change in pull request #23266: [SPARK-26313][SQL] move
`newScanBuilder` from Table to read related mix-in traits
URL: https://github.com/apache/spark/pull/23266#discussion_r241298370
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File path: sql/core/src/main/java/org/apache/spark/sql/sources/v2/Table.java
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@@ -43,17 +41,8 @@
String name();
/**
- * Returns the schema of this table.
+ * Returns the schema of this table. If the table is not readable and
doesn't have a schema, an
+ * empty schema can be returned here.
*/
StructType schema();
Review comment:
I think schema is a property of table, it should be consistent between read
and write.
But you do have a point that, fetching schema can be potentially expensive,
and we shouldn't do it at write side if validation is not needed.
We discussed this in the data source v2 community meeting today. We will
introduce a capability API, so that data source can tell Spark it doesn't want
to do validation, and Spark would not call `schema()`.
Does it sound good to you?
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