Github user arina-ielchiieva commented on a diff in the pull request:
https://github.com/apache/drill/pull/1032#discussion_r151732407
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/DynamicRootSchema.java
---
@@ -0,0 +1,140 @@
+/*
+ * 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.drill.exec.planner.sql;
+
+import com.google.common.collect.ImmutableSortedSet;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
+import org.apache.calcite.DataContext;
+import org.apache.calcite.jdbc.CalciteRootSchema;
+import org.apache.calcite.jdbc.CalciteSchema;
+
+import org.apache.calcite.linq4j.tree.Expression;
+import org.apache.calcite.linq4j.tree.Expressions;
+import org.apache.calcite.schema.SchemaPlus;
+import org.apache.calcite.schema.impl.AbstractSchema;
+import org.apache.calcite.util.BuiltInMethod;
+import org.apache.calcite.util.Compatible;
+import org.apache.drill.common.exceptions.ExecutionSetupException;
+import org.apache.drill.exec.store.SchemaConfig;
+import org.apache.drill.exec.store.StoragePlugin;
+import org.apache.drill.exec.store.StoragePluginRegistry;
+import org.apache.drill.exec.store.SubSchemaWrapper;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+import java.util.NavigableSet;
+import java.util.Set;
+
+/**
+ * This class is to allow us loading schemas from storage plugins later
when {@link #getSubSchema(String, boolean)}
+ * is called.
+ */
+public class DynamicRootSchema extends DynamicSchema
+ implements CalciteRootSchema {
+ private static final org.slf4j.Logger logger =
org.slf4j.LoggerFactory.getLogger(DynamicRootSchema.class);
+ /** Creates a root schema. */
+ DynamicRootSchema(StoragePluginRegistry storages, SchemaConfig
schemaConfig) {
+ super(null, new RootSchema(), "");
+ this.schemaConfig = schemaConfig;
+ this.storages = storages;
+ }
+
+ @Override
+ public CalciteSchema getSubSchema(String schemaName, boolean
caseSensitive) {
+ CalciteSchema retSchema = getSubSchemaMap().get(schemaName);
+ if (retSchema != null) {
+ return retSchema;
+ }
+
+ loadSchemaFactory(schemaName, caseSensitive);
+ retSchema = getSubSchemaMap().get(schemaName);
+ return retSchema;
+ }
+
+ @Override
+ public NavigableSet<String> getTableNames() {
+ Set<String> pluginNames = Sets.newHashSet();
+ for (Map.Entry<String, StoragePlugin> storageEntry :
getSchemaFactories()) {
+ pluginNames.add(storageEntry.getKey());
+ }
+ return Compatible.INSTANCE.navigableSet(
+ ImmutableSortedSet.copyOf(
+ Sets.union(pluginNames, getSubSchemaMap().keySet())));
+ }
+
+ /**
+ * load schema factory(storage plugin) for schemaName
+ * @param schemaName
+ * @param caseSensitive
+ */
+ public void loadSchemaFactory(String schemaName, boolean caseSensitive) {
+ try {
+ SchemaPlus thisPlus = this.plus();
+ StoragePlugin plugin = getSchemaFactories().getPlugin(schemaName);
+ if (plugin != null) {
+ plugin.registerSchemas(schemaConfig, thisPlus);
+ return;
+ }
+
+ // we could not find the plugin, the schemaName could be `dfs.tmp`,
a 2nd level schema under 'dfs'
+ String[] paths = schemaName.split("\\.");
+ if (paths.length == 2) {
+ plugin = getSchemaFactories().getPlugin(paths[0]);
+ if (plugin == null) {
+ return;
+ }
+
+ // we could find storage plugin for first part(e.g. 'dfs') of
schemaName (e.g. 'dfs.tmp')
+ // register schema for this storage plugin to 'this'.
+ plugin.registerSchemas(schemaConfig, thisPlus);
+
+ // we load second level schemas for this storage plugin
+ final SchemaPlus firstlevelSchema =
thisPlus.getSubSchema(paths[0]);
+ final List<SchemaPlus> secondLevelSchemas = Lists.newArrayList();
+ for (String secondLevelSchemaName :
firstlevelSchema.getSubSchemaNames()) {
+
secondLevelSchemas.add(firstlevelSchema.getSubSchema(secondLevelSchemaName));
+ }
+
+ for (SchemaPlus schema : secondLevelSchemas) {
+ org.apache.drill.exec.store.AbstractSchema drillSchema;
+ try {
+ drillSchema =
schema.unwrap(org.apache.drill.exec.store.AbstractSchema.class);
+ } catch (ClassCastException e) {
+ throw new RuntimeException(String.format("Schema '%s' is not
expected under root schema", schema.getName()));
+ }
+ SubSchemaWrapper wrapper = new SubSchemaWrapper(drillSchema);
+ thisPlus.add(wrapper.getName(), wrapper);
+ }
+ }
+ } catch(ExecutionSetupException | IOException ex) {
+ logger.warn("Failed to load schema for \"" + schemaName + "\"!", ex);
+ }
+ }
+
+ static class RootSchema extends AbstractSchema {
+ @Override public Expression getExpression(SchemaPlus parentSchema,
--- End diff --
Could you please explain why we override `getExpression` method?
---
