Github user jacques-n commented on a diff in the pull request:
https://github.com/apache/drill/pull/193#discussion_r41630368
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/handlers/NonDeferredSchemaTableLimit0Visitor.java
---
@@ -0,0 +1,126 @@
+/**
+ * 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
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * 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.drill.exec.planner.sql.handlers;
+
+import com.google.common.collect.Lists;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.RelShuttleImpl;
+import org.apache.calcite.rel.core.TableScan;
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.sql.type.SqlTypeFactoryImpl;
+import org.apache.calcite.sql.type.SqlTypeName;
+import org.apache.drill.common.exceptions.ExecutionSetupException;
+import org.apache.drill.common.expression.SchemaPath;
+import org.apache.drill.common.types.TypeProtos;
+import org.apache.drill.exec.exception.SchemaChangeException;
+import org.apache.drill.exec.expr.TypeHelper;
+import org.apache.drill.exec.ops.OperatorContext;
+import org.apache.drill.exec.physical.impl.OutputMutator;
+import org.apache.drill.exec.planner.logical.DrillConstExecutor;
+import org.apache.drill.exec.planner.logical.DrillScanRel;
+import org.apache.drill.exec.planner.logical.DrillTable;
+import org.apache.drill.exec.planner.types.DrillRelDataTypeSystem;
+import org.apache.drill.exec.record.MaterializedField;
+import org.apache.drill.exec.store.AbstractRecordReader;
+import org.apache.drill.exec.store.RecordReader;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ *
+ */
+public class NonDeferredSchemaTableLimit0Visitor extends RelShuttleImpl {
--- End diff --
I think the logic here is incorrect/incomplete. We should be:
1. traverse the entire tree to determine if all the table leaves are
FullySchemaed and the root portion of the tree is limit 0.
- For schema detection, a better possibility would be to determine if the
output is fully schemaed as opposed to all the inputs are fully schemaed. Maybe
this would work if we verify that all of the fields of the root node are not an
ANY type. @jinfengni could provide comments here.
2. If (1) is true, then we should read the schema of the root node of the
tree
3. Create a reader for the root node of the tree.
The query here can be arbitrarily complex (many joins, group bys, etc).
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
