/
SelectItemsEngine.java
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/
SelectItemsEngine.java
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/*
* 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.shardingsphere.core.optimize.statement.sharding.dml.select.item.engine;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import lombok.RequiredArgsConstructor;
import org.apache.shardingsphere.core.metadata.table.ShardingTableMetaData;
import org.apache.shardingsphere.core.optimize.statement.sharding.dml.select.groupby.GroupBy;
import org.apache.shardingsphere.core.optimize.statement.sharding.dml.select.item.DerivedCommonSelectItem;
import org.apache.shardingsphere.core.optimize.statement.sharding.dml.select.item.SelectItem;
import org.apache.shardingsphere.core.optimize.statement.sharding.dml.select.item.SelectItems;
import org.apache.shardingsphere.core.optimize.statement.sharding.dml.select.item.ShorthandSelectItem;
import org.apache.shardingsphere.core.optimize.statement.sharding.dml.select.orderby.OrderBy;
import org.apache.shardingsphere.core.optimize.statement.sharding.dml.select.orderby.OrderByItem;
import org.apache.shardingsphere.core.parse.constant.DerivedColumn;
import org.apache.shardingsphere.core.parse.sql.context.table.Table;
import org.apache.shardingsphere.core.parse.sql.segment.dml.SelectItemsSegment;
import org.apache.shardingsphere.core.parse.sql.segment.dml.item.SelectItemSegment;
import org.apache.shardingsphere.core.parse.sql.segment.dml.order.item.ColumnOrderByItemSegment;
import org.apache.shardingsphere.core.parse.sql.segment.dml.order.item.IndexOrderByItemSegment;
import org.apache.shardingsphere.core.parse.sql.segment.dml.order.item.OrderByItemSegment;
import org.apache.shardingsphere.core.parse.sql.segment.dml.order.item.TextOrderByItemSegment;
import org.apache.shardingsphere.core.parse.sql.statement.SQLStatement;
import org.apache.shardingsphere.core.parse.sql.statement.dml.SelectStatement;
import java.util.Collection;
import java.util.LinkedList;
/**
* Select items engine.
*
* @author zhangliang
*/
@RequiredArgsConstructor
public final class SelectItemsEngine {
private final ShardingTableMetaData shardingTableMetaData;
private final SelectItemEngine selectItemEngine = new SelectItemEngine();
/**
* Create select items.
*
* @param selectStatement SQL statement
* @param groupBy group by
* @param orderBy order by
* @return select items
*/
public SelectItems createSelectItems(final SelectStatement selectStatement, final GroupBy groupBy, final OrderBy orderBy) {
SelectItemsSegment selectItemsSegment = getSelectItemsSegment(selectStatement);
Collection<SelectItem> items = getSelectItemList(selectItemsSegment, selectStatement);
SelectItems result = new SelectItems(items, selectItemsSegment.isDistinctRow(), selectItemsSegment.getStopIndex());
result.getItems().addAll(getDerivedGroupByColumns(selectStatement, items, groupBy));
result.getItems().addAll(getDerivedOrderByColumns(selectStatement, items, orderBy));
return result;
}
private SelectItemsSegment getSelectItemsSegment(final SelectStatement selectStatement) {
Optional<SelectItemsSegment> result = selectStatement.findSQLSegment(SelectItemsSegment.class);
Preconditions.checkState(result.isPresent());
return result.get();
}
private Collection<SelectItem> getSelectItemList(final SelectItemsSegment selectItemsSegment, final SQLStatement sqlStatement) {
Collection<SelectItem> result = new LinkedList<>();
for (SelectItemSegment each : selectItemsSegment.getSelectItems()) {
Optional<SelectItem> selectItem = selectItemEngine.createSelectItem(each, sqlStatement);
if (selectItem.isPresent()) {
result.add(selectItem.get());
}
}
return result;
}
private Collection<SelectItem> getDerivedGroupByColumns(final SelectStatement selectStatement, final Collection<SelectItem> selectItems, final GroupBy groupBy) {
return getDerivedOrderColumns(selectStatement, selectItems, groupBy.getItems(), DerivedColumn.GROUP_BY_ALIAS);
}
private Collection<SelectItem> getDerivedOrderByColumns(final SelectStatement selectStatement, final Collection<SelectItem> selectItems, final OrderBy orderBy) {
return getDerivedOrderColumns(selectStatement, selectItems, orderBy.getItems(), DerivedColumn.ORDER_BY_ALIAS);
}
private Collection<SelectItem> getDerivedOrderColumns(final SelectStatement selectStatement,
final Collection<SelectItem> selectItems, final Collection<OrderByItem> orderItems, final DerivedColumn derivedColumn) {
Collection<SelectItem> result = new LinkedList<>();
int derivedColumnOffset = 0;
for (OrderByItem each : orderItems) {
if (!containsItem(selectStatement, selectItems, each.getSegment())) {
result.add(new DerivedCommonSelectItem(((TextOrderByItemSegment) each.getSegment()).getText(), derivedColumn.getDerivedColumnAlias(derivedColumnOffset++)));
}
}
return result;
}
private boolean containsItem(final SelectStatement selectStatement, final Collection<SelectItem> items, final OrderByItemSegment orderByItemSegment) {
return orderByItemSegment instanceof IndexOrderByItemSegment
|| containsItemInShorthandItems(selectStatement, items, orderByItemSegment) || containsItemInSelectItems(items, orderByItemSegment);
}
private boolean containsItemInShorthandItems(final SelectStatement selectStatement, final Collection<SelectItem> items, final OrderByItemSegment orderByItemSegment) {
return isUnqualifiedShorthandItem(items)
|| containsItemWithOwnerInShorthandItems(selectStatement, items, orderByItemSegment) || containsItemWithoutOwnerInShorthandItems(selectStatement, items, orderByItemSegment);
}
private boolean isUnqualifiedShorthandItem(final Collection<SelectItem> items) {
if (1 != items.size()) {
return false;
}
SelectItem item = items.iterator().next();
return item instanceof ShorthandSelectItem && !((ShorthandSelectItem) item).getOwner().isPresent();
}
private boolean containsItemWithOwnerInShorthandItems(final SelectStatement selectStatement, final Collection<SelectItem> items, final OrderByItemSegment orderItem) {
return orderItem instanceof ColumnOrderByItemSegment && ((ColumnOrderByItemSegment) orderItem).getColumn().getOwner().isPresent()
&& findShorthandItem(selectStatement, items, ((ColumnOrderByItemSegment) orderItem).getColumn().getOwner().get().getName()).isPresent();
}
private Optional<ShorthandSelectItem> findShorthandItem(final SelectStatement selectStatement, final Collection<SelectItem> items, final String tableNameOrAlias) {
Optional<Table> table = selectStatement.getTables().find(tableNameOrAlias);
if (!table.isPresent()) {
return Optional.absent();
}
for (SelectItem each : items) {
if (!(each instanceof ShorthandSelectItem)) {
continue;
}
ShorthandSelectItem shorthandSelectItem = (ShorthandSelectItem) each;
if (shorthandSelectItem.getOwner().isPresent() && selectStatement.getTables().find(shorthandSelectItem.getOwner().get()).equals(table)) {
return Optional.of(shorthandSelectItem);
}
}
return Optional.absent();
}
private boolean containsItemWithoutOwnerInShorthandItems(final SelectStatement selectStatement, final Collection<SelectItem> items, final OrderByItemSegment orderItem) {
if (!(orderItem instanceof ColumnOrderByItemSegment)) {
return false;
}
if (!((ColumnOrderByItemSegment) orderItem).getColumn().getOwner().isPresent()) {
for (ShorthandSelectItem each : getQualifiedShorthandItems(items)) {
if (isSameSelectItem(selectStatement, each, (ColumnOrderByItemSegment) orderItem)) {
return true;
}
}
}
return false;
}
private Collection<ShorthandSelectItem> getQualifiedShorthandItems(final Collection<SelectItem> items) {
Collection<ShorthandSelectItem> result = new LinkedList<>();
for (SelectItem each : items) {
if (each instanceof ShorthandSelectItem && ((ShorthandSelectItem) each).getOwner().isPresent()) {
result.add((ShorthandSelectItem) each);
}
}
return result;
}
private boolean isSameSelectItem(final SelectStatement selectStatement, final ShorthandSelectItem shorthandSelectItem, final ColumnOrderByItemSegment orderItem) {
Preconditions.checkState(shorthandSelectItem.getOwner().isPresent());
Optional<Table> table = selectStatement.getTables().find(shorthandSelectItem.getOwner().get());
return table.isPresent() && shardingTableMetaData.containsColumn(table.get().getName(), orderItem.getColumn().getName());
}
private boolean containsItemInSelectItems(final Collection<SelectItem> items, final OrderByItemSegment orderItem) {
for (SelectItem each : items) {
if (orderItem instanceof IndexOrderByItemSegment) {
return true;
}
if (isSameAlias(each, (TextOrderByItemSegment) orderItem) || isSameQualifiedName(each, (TextOrderByItemSegment) orderItem)) {
return true;
}
}
return false;
}
private boolean isSameAlias(final SelectItem selectItem, final TextOrderByItemSegment orderItem) {
return selectItem.getAlias().isPresent() && (orderItem.getText().equalsIgnoreCase(selectItem.getAlias().get()) || orderItem.getText().equalsIgnoreCase(selectItem.getExpression()));
}
private boolean isSameQualifiedName(final SelectItem selectItem, final TextOrderByItemSegment orderItem) {
return !selectItem.getAlias().isPresent() && selectItem.getExpression().equalsIgnoreCase(orderItem.getText());
}
}