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Posted to github@beam.apache.org by GitBox <gi...@apache.org> on 2021/10/17 00:37:37 UTC
[GitHub] [beam] robertwb commented on a change in pull request #15712: [BEAM-12976] Add Java interfaces for projection pushdown.
robertwb commented on a change in pull request #15712:
URL: https://github.com/apache/beam/pull/15712#discussion_r729995118
##########
File path: sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/ProjectionProducer.java
##########
@@ -0,0 +1,57 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.beam.sdk.schemas;
+
+import org.apache.beam.sdk.annotations.Experimental;
+
+/**
+ * A factory for operations that execute a projection on a {@link Schema}-aware {@link
+ * org.apache.beam.sdk.values.PCollection}.
+ *
+ * <p>Typically this interface will be implemented by a reader {@link
+ * org.apache.beam.sdk.transforms.PTransform} that is capable of pushing down a projection to an
+ * external source.
+ */
+@Experimental
+public interface ProjectionProducer<T> {
+ /** What kinds of projection support (if any) an operation offers. */
+ enum ProjectSupport {
+ /**
+ * No projections are supported. In other words, the operation can only return a fixed set of
+ * transforms from its input.
+ */
+ NONE,
+ /**
+ * Projections are supported as long as fields are projected in the same order as the data
+ * source.
+ */
+ WITHOUT_FIELD_REORDERING,
Review comment:
Are there cases where this is actuall required?
##########
File path: sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/ProjectionProducer.java
##########
@@ -0,0 +1,57 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.beam.sdk.schemas;
+
+import org.apache.beam.sdk.annotations.Experimental;
+
+/**
+ * A factory for operations that execute a projection on a {@link Schema}-aware {@link
+ * org.apache.beam.sdk.values.PCollection}.
+ *
+ * <p>Typically this interface will be implemented by a reader {@link
+ * org.apache.beam.sdk.transforms.PTransform} that is capable of pushing down a projection to an
+ * external source.
+ */
+@Experimental
+public interface ProjectionProducer<T> {
Review comment:
We might have DoFn -> DoFn, BoundedSource -> BoundedSource, etc. Unfortunately the Java type system isn't powerful enough to declare something as returning the same type as self. We should document this though.
##########
File path: sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/meta/provider/SchemaIOTableProviderWrapper.java
##########
@@ -153,10 +154,16 @@ public Schema getSchema() {
@Override
public ProjectSupport supportsProjects() {
PTransform<PBegin, PCollection<Row>> readerTransform = schemaIO.buildReader();
- if (readerTransform instanceof PushdownProjector) {
- return ((PushdownProjector) readerTransform).supportsFieldReordering()
- ? ProjectSupport.WITH_FIELD_REORDERING
- : ProjectSupport.WITHOUT_FIELD_REORDERING;
+ if (readerTransform instanceof ProjectionProducer) {
+ switch (((ProjectionProducer<?>) readerTransform).supportsProjectionPushdown()) {
Review comment:
Any reason not to just `return readerTransform).supportsProjectionPushdown()`?
##########
File path: sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/ProjectionProducer.java
##########
@@ -0,0 +1,57 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.beam.sdk.schemas;
+
+import org.apache.beam.sdk.annotations.Experimental;
+
+/**
+ * A factory for operations that execute a projection on a {@link Schema}-aware {@link
+ * org.apache.beam.sdk.values.PCollection}.
+ *
+ * <p>Typically this interface will be implemented by a reader {@link
+ * org.apache.beam.sdk.transforms.PTransform} that is capable of pushing down a projection to an
+ * external source.
+ */
+@Experimental
+public interface ProjectionProducer<T> {
+ /** What kinds of projection support (if any) an operation offers. */
+ enum ProjectSupport {
+ /**
+ * No projections are supported. In other words, the operation can only return a fixed set of
+ * transforms from its input.
Review comment:
Not sure what you mean by "transforms."
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