org.apache.flink.table.sources.NestedFieldsProjectableTableSource Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
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*/
package org.apache.flink.table.sources;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.table.connector.source.DynamicTableSource;
import org.apache.flink.table.connector.source.abilities.SupportsProjectionPushDown;
/**
* Adds support for projection push-down to a {@link TableSource} with nested fields.
*
* A {@link TableSource} extending this interface is able to project the fields of its returned
* {@code DataStream} if it is a {@code StreamTableSource}.
*
* @param The return type of the {@link TableSource}.
* @deprecated This interface will not be supported in the new source design around {@link
* DynamicTableSource}. Use {@link SupportsProjectionPushDown} instead. See FLIP-95 for more
* information.
*/
@Deprecated
@PublicEvolving
public interface NestedFieldsProjectableTableSource {
/**
* Creates a copy of the {@link TableSource} that projects its output to the given field
* indexes. The field indexes relate to the physical produced data type ({@link
* TableSource#getProducedDataType()}) and not to the table schema ({@link
* TableSource#getTableSchema()} of the {@link TableSource}.
*
* The table schema ({@link TableSource#getTableSchema()} of the {@link TableSource} copy
* must not be modified by this method, but only the produced data type ({@link
* TableSource#getProducedDataType()}) and the produced {@code DataStream} ({@code
* StreamTableSource.getDataStream()}). The produced data type may only be changed by removing
* or reordering first level fields. The type of the first level fields must not be changed.
*
*
If the {@link TableSource} implements the {@link DefinedFieldMapping} interface, it might
* be necessary to adjust the mapping as well.
*
*
The {@code nestedFields} parameter contains all nested fields that are accessed by the
* query. This information can be used to only read and set the accessed fields. Non-accessed
* fields may be left empty, set to null, or to a default value.
*
*
This method is called with parameters as shown in the example below:
*
*
{@code
* // schema
* tableSchema = {
* id,
* student<\school<\city, tuition>, age, name>,
* teacher<\age, name>
* }
*
* // query
* select (id, student.school.city, student.age, teacher)
*
* // parameters
* fields = field = [0, 1, 2]
* nestedFields \[\["*"], ["school.city", "age"], ["*"\]\]
* }
*
* IMPORTANT: This method must return a true copy and must not modify the original table
* source object.
*
* @param fields The indexes of the fields to return.
* @param nestedFields The paths of all nested fields which are accessed by the query. All other
* nested fields may be empty.
* @return A copy of the {@link TableSource} that projects its output.
*/
TableSource projectNestedFields(int[] fields, String[][] nestedFields);
}