HyukjinKwon 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_r241289160
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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:
Eh, sorry if I missed something. I guess `SupportsBatchWrite` is also going
to extend `Table` .. Am I correct?
Let's suppose one datasource implements both read support and write support.
How the implemented datasource knows we're in read side or write side when
`schema` is called?
The source might not be able to know the schema, or fetching schema can be
potentially expensive. We need a way to distinguish. Otherwise, the interface
will force to read the schema everytime, which might not be able every time, or
potentially expensive.
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