Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/16626#discussion_r107063198
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala
---
@@ -296,6 +311,47 @@ class SessionCatalog(
}
/**
+ * Alter the schema of a table identified by the provided table
identifier. The new schema
+ * should still contain the existing bucket columns and partition
columns used by the table. This
+ * method will also update any Spark SQL-related parameters stored as
Hive table properties (such
+ * as the schema itself).
+ *
+ * @param identifier TableIdentifier
+ * @param newSchema Updated schema to be used for the table (must
contain existing partition and
+ * bucket columns, and partition columns need to be at
the end)
+ */
+ def alterTableSchema(
+ identifier: TableIdentifier,
+ newSchema: StructType): Unit = {
+ val db =
formatDatabaseName(identifier.database.getOrElse(getCurrentDatabase))
+ val table = formatTableName(identifier.table)
+ val tableIdentifier = TableIdentifier(table, Some(db))
+ requireDbExists(db)
+ requireTableExists(tableIdentifier)
+ checkDuplication(newSchema)
+
+ val catalogTable = externalCatalog.getTable(db, table)
+ val oldSchema = catalogTable.schema
+
+ // not supporting dropping columns yet
+ val nonExistentColumnNames =
oldSchema.map(_.name).filterNot(columnNameResolved(newSchema, _))
+ if (nonExistentColumnNames.nonEmpty) {
+ throw new AnalysisException(
+ s"""
+ |Some existing schema fields
(${nonExistentColumnNames.mkString("[", ",", "]")}) are
+ |not present in the new schema. We don't support dropping
columns yet.
+ """.stripMargin)
+ }
+
+ // assuming the newSchema has all partition columns at the end as
required
+ externalCatalog.alterTableSchema(db, table, StructType(newSchema))
+ }
+
+ def columnNameResolved(schema: StructType, colName: String): Boolean = {
--- End diff --
private?
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