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https://issues.apache.org/jira/browse/BEAM-12609?focusedWorklogId=628042&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-628042
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ASF GitHub Bot logged work on BEAM-12609:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 26/Jul/21 22:30
Start Date: 26/Jul/21 22:30
Worklog Time Spent: 10m
Work Description: apilloud commented on a change in pull request #15216:
URL: https://github.com/apache/beam/pull/15216#discussion_r676983861
##########
File path:
sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/io/PushdownProjector.java
##########
@@ -0,0 +1,48 @@
+/*
+ * 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.io;
+
+import org.apache.beam.sdk.annotations.Experimental;
+import org.apache.beam.sdk.schemas.FieldAccessDescriptor;
+import org.apache.beam.sdk.transforms.PTransform;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.PInput;
+import org.apache.beam.sdk.values.Row;
+
+/**
+ * Factory for creating a {@link PTransform} that can execute a projection.
+ *
+ * <p>Typically this interface will be implemented by a reader {@link
PTransform} that is capable of
+ * pushing down projection to an external source. For example, {@link
SchemaIO#buildReader()} may
+ * return a {@link PushdownProjector} to which a projection may be applied
later.
+ */
+@Experimental
+public interface PushdownProjector {
+ /**
+ * Returns a {@link PTransform} that will execute the projection specified
by the {@link
+ * FieldAccessDescriptor}.
+ */
+ PTransform<? extends PInput, PCollection<Row>> withProjectionPushdown(
Review comment:
Awesome.
##########
File path:
sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/meta/provider/SchemaIOTableProviderWrapper.java
##########
@@ -118,6 +123,34 @@ public Schema getSchema() {
return begin.apply(readerTransform);
}
+ @Override
+ public PCollection<Row> buildIOReader(
+ PBegin begin, BeamSqlTableFilter filters, List<String> fieldNames) {
+ PTransform<PBegin, PCollection<Row>> readerTransform =
schemaIO.buildReader();
+ if (readerTransform instanceof PushdownProjector) {
+ PushdownProjector pushdownProjector = (PushdownProjector)
readerTransform;
+ FieldAccessDescriptor fieldAccessDescriptor =
+ FieldAccessDescriptor.withFieldNames(fieldNames);
+ // The pushdown must return a PTransform that can be applied to a
PBegin, or this cast will
+ // fail.
+ readerTransform =
+ (PTransform<PBegin, PCollection<Row>>)
+
pushdownProjector.withProjectionPushdown(fieldAccessDescriptor);
+ }
Review comment:
Shouldn't this have an `else` that looks something like `BaseBeamTable`
and reject attempts to push down if it isn't supported? You should probably
also reject filter pushdown (the `if (!(filters instanceof DefaultTableFilter))
{` block).
https://github.com/apache/beam/blob/243128a8fc52798e1b58b0cf1a271d95ee7aa241/sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/meta/BaseBeamTable.java#L30
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Issue Time Tracking
-------------------
Worklog Id: (was: 628042)
Time Spent: 0.5h (was: 20m)
> Projection pushdown in SchemaIO
> -------------------------------
>
> Key: BEAM-12609
> URL: https://issues.apache.org/jira/browse/BEAM-12609
> Project: Beam
> Issue Type: New Feature
> Components: sdk-java-core
> Reporter: Kyle Weaver
> Assignee: Kyle Weaver
> Priority: P2
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> https://docs.google.com/document/d/1M71LrbjfPZwk5C0IpI13Su63UWSBFKYjSrz9SsyBM_Y/edit
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