/*
* Copyright 1999-2017 Alibaba Group Holding Ltd.
*
* 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.
*/
package com.alibaba.druid.sql.dialect.oracle.visitor;
import com.alibaba.druid.sql.ast.SQLExpr;
import com.alibaba.druid.sql.ast.expr.SQLBinaryOpExpr;
import com.alibaba.druid.sql.ast.expr.SQLBinaryOperator;
import com.alibaba.druid.sql.ast.expr.SQLIdentifierExpr;
import com.alibaba.druid.sql.ast.expr.SQLIntegerExpr;
import com.alibaba.druid.sql.ast.statement.SQLSelect;
import com.alibaba.druid.sql.ast.statement.SQLSelectItem;
import com.alibaba.druid.sql.ast.statement.SQLSelectQueryBlock;
import com.alibaba.druid.sql.ast.statement.SQLSelectStatement;
import com.alibaba.druid.sql.ast.statement.SQLSubqueryTableSource;
import com.alibaba.druid.sql.ast.statement.SQLTableSource;
import com.alibaba.druid.sql.dialect.oracle.ast.stmt.OracleSelectQueryBlock;
public class OracleToMySqlOutputVisitor extends OracleOutputVisitor {
public OracleToMySqlOutputVisitor(Appendable appender, boolean printPostSemi){
super(appender, printPostSemi);
}
public OracleToMySqlOutputVisitor(Appendable appender){
super(appender);
}
public boolean visit(OracleSelectQueryBlock x) {
boolean parentIsSelectStatment = false;
{
if (x.getParent() instanceof SQLSelect) {
SQLSelect select = (SQLSelect) x.getParent();
if (select.getParent() instanceof SQLSelectStatement || select.getParent() instanceof SQLSubqueryTableSource) {
parentIsSelectStatment = true;
}
}
}
if (!parentIsSelectStatment) {
return super.visit(x);
}
if (x.getWhere() instanceof SQLBinaryOpExpr //
&& x.getFrom() instanceof SQLSubqueryTableSource //
) {
int rownum;
String ident;
SQLBinaryOpExpr where = (SQLBinaryOpExpr) x.getWhere();
if (where.getRight() instanceof SQLIntegerExpr && where.getLeft() instanceof SQLIdentifierExpr) {
rownum = ((SQLIntegerExpr) where.getRight()).getNumber().intValue();
ident = ((SQLIdentifierExpr) where.getLeft()).getName();
} else {
return super.visit(x);
}
SQLSelect select = ((SQLSubqueryTableSource) x.getFrom()).getSelect();
SQLSelectQueryBlock queryBlock = null;
SQLSelect subSelect = null;
SQLBinaryOpExpr subWhere = null;
boolean isSubQueryRowNumMapping = false;
if (select.getQuery() instanceof SQLSelectQueryBlock) {
queryBlock = (SQLSelectQueryBlock) select.getQuery();
if (queryBlock.getWhere() instanceof SQLBinaryOpExpr) {
subWhere = (SQLBinaryOpExpr) queryBlock.getWhere();
}
for (SQLSelectItem selectItem : queryBlock.getSelectList()) {
if (isRowNumber(selectItem.getExpr())) {
if (where.getLeft() instanceof SQLIdentifierExpr
&& ((SQLIdentifierExpr) where.getLeft()).getName().equals(selectItem.getAlias())) {
isSubQueryRowNumMapping = true;
}
}
}
SQLTableSource subTableSource = queryBlock.getFrom();
if (subTableSource instanceof SQLSubqueryTableSource) {
subSelect = ((SQLSubqueryTableSource) subTableSource).getSelect();
}
}
if ("ROWNUM".equalsIgnoreCase(ident)) {
SQLBinaryOperator op = where.getOperator();
Integer limit = null;
if (op == SQLBinaryOperator.LessThanOrEqual) {
limit = rownum;
} else if (op == SQLBinaryOperator.LessThan) {
limit = rownum - 1;
}
if (limit != null) {
select.accept(this);
println();
print0(ucase ? "LIMIT " : "limit ");
print(limit);
return false;
}
} else if (isSubQueryRowNumMapping) {
SQLBinaryOperator op = where.getOperator();
SQLBinaryOperator subOp = subWhere.getOperator();
if (isRowNumber(subWhere.getLeft()) //
&& subWhere.getRight() instanceof SQLIntegerExpr) {
int subRownum = ((SQLIntegerExpr) subWhere.getRight()).getNumber().intValue();
Integer offset = null;
if (op == SQLBinaryOperator.GreaterThanOrEqual) {
offset = rownum + 1;
} else if (op == SQLBinaryOperator.GreaterThan) {
offset = rownum;
}
if (offset != null) {
Integer limit = null;
if (subOp == SQLBinaryOperator.LessThanOrEqual) {
limit = subRownum - offset;
} else if (subOp == SQLBinaryOperator.LessThan) {
limit = subRownum - 1 - offset;
}
if (limit != null) {
subSelect.accept(this);
println();
print0(ucase ? "LIMIT " : "limit ");
print(offset);
print0(", ");
print(limit);
return false;
}
}
}
}
}
return super.visit(x);
}
static boolean isRowNumber(SQLExpr expr) {
if (expr instanceof SQLIdentifierExpr) {
String lownerName = ((SQLIdentifierExpr) expr).getLowerName();
return "rownum".equals(lownerName);
}
return false;
}
}