Github user chunhui-shi commented on a diff in the pull request: https://github.com/apache/drill/pull/1032#discussion_r152073873 --- 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); --- End diff -- we get to this place only when that split got an array of length 2 and after we check nullability of plugin, so 'plugin' in this line should not be null if this is your concern.
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