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The descriptors TableDescriptor/Schema only defines the meta information (just like DDL string) used to build the CatalogTable. The implementation of TableEnvironment#createTemporaryTable(path, descriptor) will translate the descriptor into CatalogTable.

TableDescriptor stores the meta information in the package-visible member fields/methods, e.g. schema, partitionedKeys, connectorOptions(), so does the Schema class. 

TableEnvironmentImpl#createTemporaryTable will create a new instance of TableDescriptorRegistration to register descriptor as a CatalogTable into catalog. It is an @Internal class located in org.apache.flink.table.descriptors. So that TableDescriptorRegistration can access member fields in TableDescriptor/Schema. TableDescriptorRegistration will convert schema into TableSchema (with the help of CatalogTableSchemaResolver), and convert partitionedKeys, options, tableSchema into CatalogTableImpl. 

TableEnvironment#from(descriptor) will register descriptor under a system generated table path (just like TableImpl#toString) first, and scan from the table path to get derive the Table. Table#executeInsert Table#executeInsert() does it in the similar way. 

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