eagle-core/eagle-query/eagle-entity-base/src/main/java/org/apache/eagle/log/entity/GenericEntityStreamReader.java

/*
 * 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.eagle.log.entity;

import org.apache.eagle.log.entity.index.NonClusteredIndexStreamReader;
import org.apache.eagle.log.entity.index.UniqueIndexStreamReader;
import org.apache.eagle.log.entity.meta.EntityDefinition;
import org.apache.eagle.log.entity.meta.EntityDefinitionManager;
import org.apache.eagle.log.entity.meta.IndexDefinition;
import org.apache.eagle.query.parser.ORExpression;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.List;

public class GenericEntityStreamReader extends StreamReader {
    private static final Logger LOG = LoggerFactory.getLogger(GenericEntityStreamReader.class);

    private EntityDefinition entityDef;
    private SearchCondition condition;
    private String prefix;
    private StreamReader readerAfterPlan;

    public GenericEntityStreamReader(String serviceName, SearchCondition condition)
        throws InstantiationException, IllegalAccessException {
        this(serviceName, condition, null);
    }

    public GenericEntityStreamReader(EntityDefinition entityDef, SearchCondition condition)
        throws InstantiationException, IllegalAccessException {
        this(entityDef, condition, entityDef.getPrefix());
    }

    public GenericEntityStreamReader(String serviceName, SearchCondition condition, String prefix)
        throws InstantiationException, IllegalAccessException {
        this.prefix = prefix;
        checkNotNull(serviceName, "serviceName");
        this.entityDef = EntityDefinitionManager.getEntityByServiceName(serviceName);
        checkNotNull(entityDef, "EntityDefinition");
        this.condition = condition;
        this.readerAfterPlan = selectQueryReader();
    }

    public GenericEntityStreamReader(EntityDefinition entityDef, SearchCondition condition, String prefix)
        throws InstantiationException, IllegalAccessException {
        this.prefix = prefix;
        checkNotNull(entityDef, "entityDef");
        this.entityDef = entityDef;
        checkNotNull(entityDef, "EntityDefinition");
        this.condition = condition;
        this.readerAfterPlan = selectQueryReader();
    }

    private void checkNotNull(Object o, String message) {
        if (o == null) {
            throw new IllegalArgumentException(message + " should not be null");
        }
    }

    public EntityDefinition getEntityDefinition() {
        return entityDef;
    }

    public SearchCondition getSearchCondition() {
        return condition;
    }

    @Override
    public void readAsStream() throws Exception {
        readerAfterPlan.listeners.addAll(this.listeners);
        readerAfterPlan.readAsStream();
    }

    private StreamReader selectQueryReader() throws InstantiationException, IllegalAccessException {
        final ORExpression query = condition.getQueryExpression();
        IndexDefinition[] indexDefs = entityDef.getIndexes();

        // Index just works with query condition
        if (indexDefs != null && condition.getQueryExpression() != null) {
            List<byte[]> rowkeys = new ArrayList<>();
            for (IndexDefinition index : indexDefs) {
                // Check unique index first
                if (index.isUnique()) {
                    final IndexDefinition.IndexType type = index.canGoThroughIndex(query, rowkeys);
                    if (!IndexDefinition.IndexType.NON_INDEX.equals(type)) {
                        LOG.info("Selectd query unique index " + index.getIndexName() + " for query: "
                                 + condition.getQueryExpression());
                        return new UniqueIndexStreamReader(index, condition, rowkeys);
                    }
                }
            }
            for (IndexDefinition index : indexDefs) {
                // Check non-clustered index
                if (!index.isUnique()) {
                    final IndexDefinition.IndexType type = index.canGoThroughIndex(query, rowkeys);
                    if (!IndexDefinition.IndexType.NON_INDEX.equals(type)) {
                        LOG.info("Selectd query non clustered index " + index.getIndexName() + " for query: "
                                 + condition.getQueryExpression().toString());
                        return new NonClusteredIndexStreamReader(index, condition, rowkeys);
                    }
                }
            }
        }
        return new GenericEntityScanStreamReader(entityDef, condition, this.prefix);
    }

    @Override
    public long getLastTimestamp() {
        return readerAfterPlan.getLastTimestamp();
    }

    @Override
    public long getFirstTimestamp() {
        return readerAfterPlan.getFirstTimestamp();
    }
}