/*
* Copyright 1999-2015 dangdang.com.
* <p>
* Licensed 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.
* </p>
*/
package com.dangdang.ddframe.rdb.sharding.parser.visitor.basic.mysql;
import com.alibaba.druid.sql.ast.SQLExpr;
import com.alibaba.druid.sql.ast.SQLOrderBy;
import com.alibaba.druid.sql.ast.expr.SQLAggregateExpr;
import com.alibaba.druid.sql.ast.expr.SQLAllColumnExpr;
import com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr;
import com.alibaba.druid.sql.ast.expr.SQLIntegerExpr;
import com.alibaba.druid.sql.ast.expr.SQLNumericLiteralExpr;
import com.alibaba.druid.sql.ast.expr.SQLPropertyExpr;
import com.alibaba.druid.sql.ast.expr.SQLVariantRefExpr;
import com.alibaba.druid.sql.ast.statement.SQLExprTableSource;
import com.alibaba.druid.sql.ast.statement.SQLSelectItem;
import com.alibaba.druid.sql.ast.statement.SQLSelectOrderByItem;
import com.alibaba.druid.sql.dialect.mysql.ast.expr.MySqlSelectGroupByExpr;
import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlSelectQueryBlock;
import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlOutputVisitor;
import com.dangdang.ddframe.rdb.sharding.exception.SQLParserException;
import com.dangdang.ddframe.rdb.sharding.parser.result.merger.AbstractSortableColumn;
import com.dangdang.ddframe.rdb.sharding.parser.result.merger.AggregationColumn;
import com.dangdang.ddframe.rdb.sharding.parser.result.merger.AggregationColumn.AggregationType;
import com.dangdang.ddframe.rdb.sharding.parser.result.merger.Limit;
import com.dangdang.ddframe.rdb.sharding.parser.result.merger.OrderByColumn.OrderByType;
import com.google.common.base.Optional;
import com.google.common.base.Strings;
import java.util.List;
/**
* MySQL的SELECT语句访问器.
*
* @author gaohongtao
* @author zhangliang
*/
public class MySQLSelectVisitor extends AbstractMySQLVisitor {
@Override
protected void printSelectList(final List<SQLSelectItem> selectList) {
super.printSelectList(selectList);
// TODO 提炼成print，或者是否不应该由token的方式替换？
printToken(getParseContext().getAutoGenTokenKey(), null);
}
@Override
public boolean visit(final MySqlSelectQueryBlock x) {
stepInQuery();
if (x.getFrom() instanceof SQLExprTableSource) {
SQLExprTableSource tableExpr = (SQLExprTableSource) x.getFrom();
getParseContext().setCurrentTable(tableExpr.getExpr().toString(), Optional.fromNullable(tableExpr.getAlias()));
}
return super.visit(x);
}
/**
* 解析 {@code SELECT item1,item2 FROM }中的item.
*
* @param x SELECT item 表达式
* @return true表示继续遍历AST, false表示终止遍历AST
*/
// TODO SELECT * 导致index不准，不支持SELECT *，且生产环境不建议使用SELECT *
public boolean visit(final SQLSelectItem x) {
getParseContext().increaseItemIndex();
if (Strings.isNullOrEmpty(x.getAlias())) {
SQLExpr expr = x.getExpr();
if (expr instanceof SQLIdentifierExpr) {
getParseContext().registerSelectItem(((SQLIdentifierExpr) expr).getName());
} else if (expr instanceof SQLPropertyExpr) {
getParseContext().registerSelectItem(((SQLPropertyExpr) expr).getName());
} else if (expr instanceof SQLAllColumnExpr) {
getParseContext().registerSelectItem("*");
}
} else {
getParseContext().registerSelectItem(x.getAlias());
}
return super.visit(x);
}
@Override
public boolean visit(final SQLAggregateExpr x) {
if (!(x.getParent() instanceof SQLSelectItem)) {
return super.visit(x);
}
AggregationType aggregationType;
try {
aggregationType = AggregationType.valueOf(x.getMethodName().toUpperCase());
} catch (final IllegalArgumentException ex) {
return super.visit(x);
}
StringBuilder expression = new StringBuilder();
x.accept(new MySqlOutputVisitor(expression));
// TODO index获取不准，考虑使用别名替换
AggregationColumn column = new AggregationColumn(expression.toString(), aggregationType, Optional.fromNullable(((SQLSelectItem) x.getParent()).getAlias()),
null == x.getOption() ? Optional.<String>absent() : Optional.of(x.getOption().toString()), getParseContext().getItemIndex());
getParseContext().getParsedResult().getMergeContext().getAggregationColumns().add(column);
if (AggregationType.AVG.equals(aggregationType)) {
getParseContext().addDerivedColumnsForAvgColumn(column);
// TODO 将AVG列替换成常数，避免数据库再计算无用的AVG函数
}
return super.visit(x);
}
public boolean visit(final SQLOrderBy x) {
for (SQLSelectOrderByItem each : x.getItems()) {
SQLExpr expr = each.getExpr();
OrderByType orderByType = null == each.getType() ? OrderByType.ASC : OrderByType.valueOf(each.getType());
if (expr instanceof SQLIntegerExpr) {
getParseContext().addOrderByColumn(((SQLIntegerExpr) expr).getNumber().intValue(), orderByType);
} else if (expr instanceof SQLIdentifierExpr) {
getParseContext().addOrderByColumn(Optional.<String>absent(), ((SQLIdentifierExpr) expr).getName(), orderByType);
} else if (expr instanceof SQLPropertyExpr) {
SQLPropertyExpr sqlPropertyExpr = (SQLPropertyExpr) expr;
getParseContext().addOrderByColumn(Optional.of(sqlPropertyExpr.getOwner().toString()), sqlPropertyExpr.getName(), orderByType);
}
}
return super.visit(x);
}
/**
* 将GROUP BY列放入parseResult.
* 直接返回false,防止重复解析GROUP BY表达式.
*
* @param x GROUP BY 表达式
* @return false 停止遍历AST
*/
@Override
public boolean visit(final MySqlSelectGroupByExpr x) {
OrderByType orderByType = null == x.getType() ? OrderByType.ASC : OrderByType.valueOf(x.getType());
if (x.getExpr() instanceof SQLPropertyExpr) {
SQLPropertyExpr expr = (SQLPropertyExpr) x.getExpr();
getParseContext().addGroupByColumns(Optional.of(expr.getOwner().toString()), expr.getName(), orderByType);
} else if (x.getExpr() instanceof SQLIdentifierExpr) {
SQLIdentifierExpr expr = (SQLIdentifierExpr) x.getExpr();
getParseContext().addGroupByColumns(Optional.<String>absent(), expr.getName(), orderByType);
}
return super.visit(x);
}
/**
* LIMIT 解析.
*
* @param x LIMIT表达式
* @return false 停止遍历AST
*/
@Override
public boolean visit(final MySqlSelectQueryBlock.Limit x) {
if (getParseContext().getParseContextIndex() > 0) {
return super.visit(x);
}
print("LIMIT ");
int offset = 0;
int offSetIndex = -1;
if (null != x.getOffset()) {
if (x.getOffset() instanceof SQLNumericLiteralExpr) {
offset = ((SQLNumericLiteralExpr) x.getOffset()).getNumber().intValue();
printToken(Limit.OFFSET_NAME, String.valueOf(offset));
print(", ");
} else {
offset = ((Number) getParameters().get(((SQLVariantRefExpr) x.getOffset()).getIndex())).intValue();
offSetIndex = ((SQLVariantRefExpr) x.getOffset()).getIndex();
print("?, ");
}
}
int rowCount;
int rowCountIndex = -1;
if (x.getRowCount() instanceof SQLNumericLiteralExpr) {
rowCount = ((SQLNumericLiteralExpr) x.getRowCount()).getNumber().intValue();
printToken(Limit.COUNT_NAME, String.valueOf(rowCount));
} else {
rowCount = ((Number) getParameters().get(((SQLVariantRefExpr) x.getRowCount()).getIndex())).intValue();
rowCountIndex = ((SQLVariantRefExpr) x.getRowCount()).getIndex();
print("?");
}
if (offset < 0 || rowCount < 0) {
throw new SQLParserException("LIMIT offset and row count can not be a negative value");
}
// "LIMIT {rowCount} OFFSET {offset}" will transform to "LIMIT {offset}, {rowCount}".So exchange parameter index
if (offSetIndex > -1 && rowCountIndex > -1 && offSetIndex > rowCountIndex) {
int tmp = rowCountIndex;
rowCountIndex = offSetIndex;
offSetIndex = tmp;
}
getParseContext().getParsedResult().getMergeContext().setLimit(new Limit(offset, rowCount, offSetIndex, rowCountIndex));
return false;
}
@Override
public void endVisit(final MySqlSelectQueryBlock x) {
StringBuilder derivedSelectItems = new StringBuilder();
for (AggregationColumn aggregationColumn : getParseContext().getParsedResult().getMergeContext().getAggregationColumns()) {
for (AggregationColumn derivedColumn : aggregationColumn.getDerivedColumns()) {
derivedSelectItems.append(", ").append(derivedColumn.getExpression()).append(" AS ").append(derivedColumn.getAlias().get());
}
}
appendSortableColumn(derivedSelectItems, getParseContext().getParsedResult().getMergeContext().getGroupByColumns());
appendSortableColumn(derivedSelectItems, getParseContext().getParsedResult().getMergeContext().getOrderByColumns());
if (0 != derivedSelectItems.length()) {
getSQLBuilder().buildSQL(getParseContext().getAutoGenTokenKey(), derivedSelectItems.toString(), true);
}
super.endVisit(x);
stepOutQuery();
}
private void appendSortableColumn(final StringBuilder derivedSelectItems, final List<? extends AbstractSortableColumn> sortableColumns) {
for (AbstractSortableColumn each : sortableColumns) {
if (!each.getAlias().isPresent()) {
continue;
}
derivedSelectItems.append(", ");
if (each.getOwner().isPresent()) {
derivedSelectItems.append(each.getOwner().get()).append(".");
}
derivedSelectItems.append(each.getName().get()).append(" AS ").append(each.getAlias().get());
}
}
}